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1. A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from the Herschel Gould Belt survey⋆,⋆⋆,⋆⋆⋆

Author: Vera Könyves, P. Didelon, Matthew James Griffin, T. Hill, P. Palmeirim, Alexander Men'shchikov, Doris Arzoumanian, Stefano Pezzuto, Sarah Sadavoy, Kenneth A. Marsh, Glenn J. White, Ph. André, E. Schisano, Yoshito Shimajiri, J. Di Francesco, L. Spinoglio, Sylvain Bontemps, Peter G. Martin, Milena Benedettini, J.-Ph. Bernard, Nicola Schneider, Derek Ward-Thompson, Kazi L.J. Rygl, Jason M. Kirk, Frédérique Motte, A. Roy, Anaëlle Maury, Bilal Ladjelate, Helene Roussel, Q. Nguyen Luong, Nicolas Peretto, Davide Elia, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Département d'Astrophysique (ex SAP) (DAP), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Department of Physics and Astronomy [Victoria], University of Victoria [Canada] (UVIC), School of Physics and Astronomy [Cardiff], Cardiff University, Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Istituto Nazionale di Astrofisica (INAF), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Joint ALMA Observatory (JAO), National Radio Astronomy Observatory (NRAO)-European Southern Observatory (ESO), Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy [Preston], University of Central Lancashire [Preston] (UCLAN), Canadian Institute for Theoretical Astrophysics (CITA), Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astronomico di Bologna (OABO), Department of Physics and Astronomy [Milton Keynes], The Open University [Milton Keynes] (OU), ANR-11-BS56-0010,STARFICH,Vers une vision unifiée de la formation stellaire dans les galaxies : Origine de la structure filamentaire du milieu interstellaire, des cœurs pré-stellaires et des amas protostellaires vus avec Herschel(2011), European Project: 291294,EC:FP7:ERC,ERC-2011-ADG_20110209,ORISTARS(2012), European Project: 267934,EC:FP7:ERC,ERC-2010-AdG_20100224,MISTIC(2011), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], San Pedro de Atacama Celestial Explorations (SPACE), San Pedro de Atacama Celestial Explorations, University of California [Los Angeles] (UCLA), University of California, Service des Photons, Atomes et Molécules (SPAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), SLAC National Accelerator Laboratory (SLAC), Stanford University, Stanford Linear Accelerator Center (SLAC), Stanford University [Stanford], Smithsonian Institution-Harvard University [Cambridge], Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), European Southern Observatory (ESO)-National Radio Astronomy Observatory (NRAO), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Harvard University-Smithsonian Institution, Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), ITA, GBR, FRA, DEU, CAN, CHL, JPN, and NLD
Subjects: Initial mass function, ISM: structure, Stars: formation, Young stellar object, FOS: Physical sciences, Budget control, F500, Efficiency, Astrophysics, Surveys, Population statistics, ISM : clouds, 7. Clean energy, Submillimeter: isms, Gravitation, ISM: individual objects, Functions, Protostar, Spatial distribution, QB, Physics, Star formation, Information dissemination, Molecular cloud, Astronomy and Astrophysics, Stars, Astrophysics - Astrophysics of Galaxies, Spire, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Coremaking, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract: We present and discuss the results of the Herschel Gould Belt survey (HGBS) observations in an 11 deg2 area of the Aquila molecular cloud complex at d 260 pc, imaged with the SPIRE and PACS photometric cameras in parallel mode from 70 μm to 500 μm. Using the multi-scale, multi-wavelength source extraction algorithm getsources, we identify a complete sample of starless dense cores and embedded (Class 0-I) protostars in this region, and analyze their global properties and spatial distributions. We find a total of 651 starless cores, 60% ± 10% of which are gravitationally bound prestellar cores, and they will likely form stars inthe future. We also detect 58 protostellar cores. The core mass function (CMF) derived for the large population of prestellar cores is very similar in shape to the stellar initial mass function (IMF), confirming earlier findings on a much stronger statistical basis and supporting the view that there is a close physical link between the stellar IMF and the prestellar CMF. The global shift in mass scale observed between the CMF and the IMF is consistent with a typical star formation efficiency of 40% at the level of an individual core. By comparing the numbers of starless cores in various density bins to the number of young stellar objects (YSOs), we estimate that the lifetime of prestellar cores is 1 Myr, which is typically 4 times longer than the core free-fall time, and that it decreases with average core density. We find a strong correlation between the spatial distribution of prestellar cores and the densest filaments observed in the Aquila complex. About 90% of the Herschel-identified prestellar cores are located above a background column density corresponding to AV 7, and 75% of them lie within filamentary structures with supercritical masses per unit length ≳16 M☉/pc. These findings support a picture wherein the cores making up the peak of the CMF (and probably responsible for the base of the IMF) result primarily from the gravitational fragmentation of marginally supercritical filaments. Given that filaments appear to dominate the mass budget of dense gas at AV> 7, our findings also suggest that the physics of prestellar core formation within filaments is responsible for a characteristic "efficiency" {SFR/M_dense ̃ 5+2-2 × 10-8 yr-1} for the star formation process in dense gas. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Figures 18, 19, and Appendices are available in electronic form at http://www.aanda.orgHerschel column density and temperature maps (FITS format) and full Tables A.1 and A.2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/584/A91
Published: 2015
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2. From forced collapse to H ii region expansion in Mon R2: Envelope density structure and age determination with Herschel

Author: Frédérique Motte, D. Ward-Thompson, Annie Zavagno, D. Russeil, Marc Sauvage, Pierre Didelon, M. Hennemann, J. Di Francesco, Thomas Rayner, L. D. Anderson, A. Rivera-Ingraham, F. Louvet, Glenn J. White, Doris Arzoumanian, Sacha Hony, Alexander Men'shchikov, Ph. André, Frédéric Galliano, Nicolas Peretto, J.-P. Bernard, Tracey Hill, Pascal Tremblin, Vianney Lebouteiller, Vera Könyves, P. Palmeirim, Q. Nguyen Luong, M. Benedettini, K. L. J. Rygl, Stefano Pezzuto, Vincent Minier, M. González, Patrick Hennebelle, Matthew James Griffin, Sylvain Bontemps, Nicola Schneider, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Exeter, Maison de la Simulation (MDLS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut National de Recherche en Informatique et en Automatique (Inria)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Joint ALMA Office, Département d'Astrophysique (ex SAP) (DAP), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, National Radio Astronomy Observatory (NRAO), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), School of Physics and Astronomy [Cardiff], Cardiff University, European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude spatiale des rayonnements (CESR), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Istituto Nazionale di Astrofisica (INAF), National Research Council of Canada (NRC), Institut de recherche en astrophysique et planétologie (IRAP), Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy [Preston], University of Central Lancashire [Preston] (UCLAN), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), ANR-08-BLAN-0241,PROBES,Etoiles Proto-OB : recherche systématique dans notre Galaxie des cibles pour ALMA(2008), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Paris-Sud - Paris 11 (UP11)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), European Space Agency (ESA), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Ionization, H II region, ISM: individual objects: Mon R2, Numerical models, ISM: structure, Extinction (astronomy), FOS: Physical sciences, Collapse (topology), F500, Astrophysics, Isothermal process, Stars: protostars, Clouds, Quenching, H II regions, Solar and Stellar Astrophysics (astro-ph.SR), Envelope (waves), QB, Physics, Dust , extinction, Molecular cloud, Astronomy and Astrophysics, Stars, Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Density of gases
Abstract: The surroundings of HII regions can have a profound influence on their development, morphology, and evolution. This paper explores the effect of the environment on H II regions in the MonR2 molecular cloud. We aim to investigate the density structure of envelopes surrounding HII regions and to determine their collapse and ionisation expansion ages. The Mon R2 molecular cloud is an ideal target since it hosts an H II region association. Column density and temperature images derived from Herschel data were used together to model the structure of HII bubbles and their surrounding envelopes. The resulting observational constraints were used to follow the development of the Mon R2 ionised regions with analytical calculations and numerical simulations. The four hot bubbles associated with H II regions are surrounded by dense, cold, and neutral gas envelopes. The radial density profiles are reminiscent of those of low-mass protostellar envelopes. The inner parts of envelopes of all four HII regions could be free-falling because they display shallow density profiles. As for their outer parts, the two compact HII regions show a density profile, which is typical of the equilibrium structure of an isothermal sphere. In contrast, the central UCHii region shows a steeper outer profile, that could be interpreted as material being forced to collapse. The size of the heated bubbles, the spectral type of the irradiating stars, and the mean initial neutral gas density are used to estimate the ionisation expansion time, texp, 0.1Myr,for the dense UCHII and compact HII regions and 0.35 Myr for the extended HII region. The envelope transition radii between the shallow and steeper density profiles are used to estimate the time elapsed since the formation of the first proto stellar embryo, Tinf : 1Myr, for the ultra-compact, 1.5 / 3Myr for the compact, and greater than 6Myr for the extended HII regions., 25pages A&A sous presse
Published: 2015
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3. Filaments in the Lupus molecular clouds

Author: Stefano Pezzuto, Davide Elia, Nicola Schneider, Sergio Molinari, Kazi L.J. Rygl, P. Palmeirim, A. M. di Giorgio, Luigi Spinoglio, J. Di Francesco, Glenn J. White, Ph. André, Derek Ward-Thompson, A. Roy, Vera Könyves, Frédérique Motte, A. Rivera-Ingraham, Pascal Tremblin, Eugenio Schisano, Quang Nguyen-Luong, Doris Arzoumanian, M. Benedettini, Tracey Hill, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Exeter, Maison de la Simulation (MDLS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut National de Recherche en Informatique et en Automatique (Inria)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), foreign laboratories (FL), CERN [Genève], INAF - Osservatorio Astronomico di Roma (OAR), Istituto Nazionale di Astrofisica (INAF), Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Département d'Astrophysique (ex SAP) (DAP), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Unité expérimentale de Pech-Rouge (PECH ROUGE), Institut National de la Recherche Agronomique (INRA), SLAC National Accelerator Laboratory (SLAC), Stanford University, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), University of Victoria [Canada] (UVIC), National Research Council of Canada (NRC), National Astronomical Observatory of Japan (NAOJ), Canadian Institute for Theoretical Astrophysics (CITA), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astronomico di Bologna (OABO), Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy [Preston], University of Central Lancashire [Preston] (UCLAN), The Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, The Open University [Milton Keynes] (OU), ANR-11-BS56-0010,STARFICH,Vers une vision unifiée de la formation stellaire dans les galaxies : Origine de la structure filamentaire du milieu interstellaire, des cœurs pré-stellaires et des amas protostellaires vus avec Herschel(2011), European Project: 291294,EC:FP7:ERC,ERC-2011-ADG_20110209,ORISTARS(2012), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université Paris-Sud - Paris 11 (UP11)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Unité d'oenologie de Pech-Rouge (MONTP PECH ROUG UE), Stanford Linear Accelerator Center (SLAC), and Stanford University [Stanford]
Subjects: Physics, stars: formation, Star formation, [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Molecular cloud, Lupus (constellation), Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, F500, Critical value, Astrophysics - Astrophysics of Galaxies, ISM: clouds, Magnetic field, Protein filament, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Gravitational collapse, Astrophysics::Earth and Planetary Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract: We have studied the filaments extracted from the column density maps of the nearby Lupus 1, 3, and 4 molecular clouds, derived from photometric maps observed with the Herschel satellite. Filaments in the Lupus clouds have quite low column densities, with a median value of $\sim$1.5$\times$10$^{21}$ cm$^{-2}$ and most have masses per unit length lower than the maximum critical value for radial gravitational collapse. Indeed, no evidence of filament contraction has been seen in the gas kinematics. We find that some filaments, that on average are thermally subcritical, contain dense cores that may eventually form stars. This is an indication that in the low column density regime, the critical condition for the formation of stars may be reached only locally and this condition is not a global property of the filament. Finally, in Lupus we find multiple observational evidences of the key role that the magnetic field plays in forming filaments, and determining their confinement and dynamical evolution., Comment: 16 pages, 16 figures
Published: 2015
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4. Gas dynamics in tidal dwarf galaxies: disc formation at z=0

Author: Peter M. Weilbacher, Bärbel S. Koribalski, Federico Lelli, Médéric Boquien, Yves Revaz, Pierre-Alain Duc, Ute Lisenfeld, Frédéric Bournaud, Jonathan Braine, Elias Brinks, Pierre-Emmanuel Belles, Stacy S. McGaugh, Case Western Reserve University [Cleveland], Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre for Astrophysics Research, University of Hertfordshire [Hatfield] (UH), CAFPE and Departamento de Fisica Teorica y del Cosmos, Universidad de Granada = University of Granada (UGR), Astrophysikalisches Institut Potsdam (AIP), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), EPFL Laboratoire d’astrophysique, Ecole Polytechnique Fédérale de Lausanne (EPFL), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Australia Telescope National Facility (ATNF), Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), European Project: 257720,EC:FP7:ERC,ERC-2010-StG_20091028,GALSICO(2011), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Universidad de Granada (UGR), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Laboratoire d'Astrophysique, Ecole Polytechnique Fédérale de Lausanne (EPFL), and Australia Telescope National Facility
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Dark matter, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxy merger, dark matter, Jansky, galaxies: interactions, Astrophysics::Solar and Stellar Astrophysics, galaxies: formation, galaxies: irregular, Astrophysics::Galaxy Astrophysics, galaxies: kinematics and dynamics, Dwarf galaxy, Physics, Astronomy and Astrophysics, galaxies: dwarf, Astrophysics - Astrophysics of Galaxies, Galaxy, Baryon, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Dissipative system, Astrophysics::Earth and Planetary Astrophysics, Event (particle physics), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Tidal dwarf galaxies (TDGs) are recycled objects that form within the collisional debris of interacting/merging galaxies. They are expected to be devoid of non-baryonic dark matter, since they can form only from dissipative material ejected from the discs of the progenitor galaxies. We investigate the gas dynamics in a sample of six bona-fide TDGs around three interacting and post-interacting systems: NGC 4694, NGC 5291, and NGC 7252 ("Atoms for Peace"). For NGC 4694 and NGC 5291 we analyse existing HI data from the Very Large Array (VLA), while for NGC 7252 we present new HI observations from the Jansky VLA together with long-slit and integral-field optical spectroscopy. For all six TDGs, the HI emission can be described by rotating disc models. These HI discs, however, have undergone less than a full rotation since the time of the interaction/merger event, raising the question of whether they are in dynamical equilibrium. Assuming that these discs are in equilibrium, the inferred dynamical masses are consistent with the observed baryonic masses, implying that TDGs are devoid of dark matter. This puts constraints on putative "dark discs" (either baryonic or non-baryonic) in the progenitor galaxies. Moreover, TDGs seem to systematically deviate from the baryonic Tully-Fisher relation. These results provide a challenging test for alternative theories like MOND., Accepted for publication on A&A. Main text (20 pages, 13 figures) + Appendix (7 pages, 6 figures)
Published: 2015
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5. HOBYS and W43, two more steps towards a Galaxy-wide understanding of star formation

Author: Motte, Frederique, Bontemps, Sylvain, Nguyen Luong, Quang, Pomies, Marie-Paule, Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.ASTR.CO] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: International audience; The HOBYS key program allows to statistically study the formation of 10-20 Msun stars in molecular complexes from the first Galactic arm toward us. HOBYS therefore starts to measure the star formation rate of the Milky Way on 1-100 pc scales. The much more extreme W43 molecular complex is located at the tip of the long bar of the Milky Way and forms stars up to 50 Msun. It displays an intense star formation activity, which may originate from its dynamical cloud formation. The HOBYS and W43 surveys are necessary steps towards Galaxy-wide studies of high-mass star formation.
Published: 2015

6. Filaments, ridges and the origin of high-mass stars and clusters in Cygnus X

Author: Bontemps, Sylvain, Schneider, N., Motte, Frederique, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Procédés, Matériaux et Energie Solaire (PROMES), and Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Astrophysics::Galaxy Astrophysics
Abstract: International audience; Recent Herschel findings on filaments in nearby low-mass star-forming clouds clearly points to a new paradigm to explain the formation of high density gas in turbulent clouds leading to the protostellar collapse. These filaments are the locations for core fragmentation at roughly the local Jeans mass. The formation of massive stars and of rich stellar clusters in this new paradigm is however not yet understood. Massive elongated/filamentary structures, referred as ridges, are massive filaments observed in regions of high-mass stars formation which may host the formation of massive stars. They have large average densities and show large velocity dispersion, and are roughly as cold as their low-mass counterparts. This may indicate that a larger effective Jeans mass in these ridges due to additional turbulent support could explain a core fragmentation extending up to higher stellar masses. The level of turbulent support in ridges is however difficult to measure due a high level of dynamics (flows, rotation, infall) which may not represent well the level of true support (isotropic) for Jeans fragmentation. More generally the structure and properties of ridges/massive filaments is not well known and requires dedicated studies.I will present our most recent results obtained with Herschel and the IRAM 30m towards the DR21 ridge in Cygnus X. Several massive protostars are actually observed in the DR21 ridge confirming it is the birth place of massive stars. I will show that the whole large scale region is compatible with a global collapse of a 15 pc cloud of several 10s of thousands of solar masses. The most recent IRAM 30m observations show that the ridge is made of several sub-filaments which are all more massive than their counterparts in low-mass star forming regions. I will discuss the implications of these results in the context of the origin of massive stars.
Published: 2015

7. COnnecting LOcal to GLObal star formation via MIni-starburst

Author: Nguyen Luong, Quang, Motte, Frederique, Nguyen, Hans, Schneider, N., Louvet, Fabien, Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), MICrobiologie de l'ALImentation au Service de la Santé (MICALIS), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Département d'Astrophysique (ex SAP) (DAP), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: International audience; To connect local to global star formation, we compare the mass, size, line width, and star formation rate (SFR) density of cloud structures ranging from Galactic clouds ($\sim$1--10~pc in size) to galaxies (with $\sim$1--10~kpc sizes).Our focus is on molecular cloud structures, called massive complexes, which have intermediate sizes of $\sim$100~pc and masses larger than $10^6~\msun$.We propose using a starburstiness quantity $\zeta$ to quantify the star formation intensity of a molecular cloud complex, or how much its SFR deviates from the star formation relations such as Kennicutt and Lada ones. For molecular cloud complex that has $\zeta>3$ , we call it mini-starburst complex, otherwise normal or main-sequence complex. This $\zeta>3$ threshold leads to a SFR threshold. Most complexes can be classified as ministarburst as having $\zeta>3$. We propose that mini-starburst events represent an enhancement of the star formation activity, following dynamic events such as compression, colliding flows, or agglomeration which compress materials within a cloud complex.
Published: 2015

8. Spatially-Resolved Dense Molecular Gas and Star Formation Rate in M51

Author: Qiusheng Gu, Hao Chen, Jonathan Braine, Yu Gao, Department of mathematics, Jiangxi Normal University, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Spiral galaxy, 010504 meteorology & atmospheric sciences, Infrared, Star formation, [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Milky Way, Molecular cloud, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Galaxy, law.invention, Telescope, Orders of magnitude (time), Space and Planetary Science, law, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, 10. No inequality, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: We present the spatially-resolved observations of HCN J = 1 -- 0 emission in the nearby spiral galaxy M51 using the IRAM 30 m telescope. The HCN map covers an extent of $4\arcmin\times5\arcmin$ with spatial resolution of $28\arcsec$, which is, so far, the largest in M51. There is a correlation between infrared emission (star formation rate indicator) and HCN (1--0) emission (dense gas tracer) at kpc scale in M51, a natural extension of the proportionality between the star formation rate (SFR) and the dense gas mass established globally in galaxies. Within M51, the relation appears to be sub-linear (with a slope of 0.74$\pm$0.16) as $L_{\rm IR}$ rises less quickly than $L_{\rm HCN}$. We attribute this to a difference between center and outer disk such that the central regions have stronger HCN (1--0) emission per unit star formation. The IR-HCN correlation in M51 is further compared with global one from Milky Way to high-z galaxies and bridges the gap between giant molecular clouds (GMCs) and galaxies. Like the centers of nearby galaxies, the $L_{\rm IR}$/$L_{\rm HCN}$ ratio measured in M51 (particularly in the central regions), is slightly lower than what is measured globally in galaxies, yet is still within the scatter. This implies that though the $L_{\rm IR}$/$L_{\rm HCN}$ ratio varies as a function of physical environment in the different positions of M51, IR and HCN indeed show a linear correlation over 10 orders of magnitude., Comment: 29 pages, 8 figures, accepted for publication in ApJ
Published: 2015
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9. Herschel Observations of the W3 GMC (II): Clues to the Formation of Clusters of High-Mass Stars

Author: A. Marston, K. L. J. Rygl, Tracey Hill, D. Polychroni, M. Hennemann, Luigi Spinoglio, Frédérique Motte, Stefano Pezzuto, Cassandra Fallscheer, Nicola Schneider, Alexander Men'shchikov, Vera Konyves, G. J. White, Annie Zavagno, A. Rivera-Ingraham, Pierrick Martin, Ph. André, Sylvain Bontemps, J. Di Francesco, Q. Nguyen Luong, J.-Ph. Bernard, Department of Applied Mathematics and Statistics, Colorado School of Mines, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire d'Astrophysique de Marseille (LAM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), SLAC National Accelerator Laboratory (SLAC), Stanford University, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Stanford Linear Accelerator Center (SLAC), and Stanford University [Stanford]
Subjects: Physics, Stellar population, 010308 nuclear & particles physics, Star formation, [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Extinction (astronomy), FOS: Physical sciences, Astronomy and Astrophysics, Probability density function, Function (mathematics), Astrophysics, 01 natural sciences, Constructive, Astrophysics - Astrophysics of Galaxies, Stars, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Log-normal distribution, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: The W3 GMC is a prime target for investigating the formation of high-mass stars and clusters. This second study of W3 within the HOBYS Key Program provides a comparative analysis of subfields within W3 to further constrain the processes leading to the observed structures and stellar population. Probability density functions (PDFs) and cumulative mass distributions (CMDs) were created from dust column density maps, quantified as extinction Av. The shape of the PDF, typically represented with a lognormal function at low Av "breaking" to a power-law tail at high Av, is influenced by various processes including turbulence and self-gravity. The breaks can also be identified, often more readily, in the CMDs. The PDF break from lognormal (Av(SF)= 6-10 mag) appears to shift to higher Av by stellar feedback, so that high-mass star-forming regions tend to have higher PDF breaks. A second break at Av > 50 mag traces structures formed or influenced by a dynamic process. Because such a process has been suggested to drive high-mass star formation in W3, this second break might then identify regions with potential for hosting high-mass stars/clusters. Stellar feedback appears to be a major mechanism driving the local evolution and state of regions within W3. A high initial star formation efficiency in a dense medium could result in a self-enhancing process, leading to more compression and favourable star-formation conditions (e.g., colliding flows), a richer stellar content, and massive stars. This scenario would be compatible with the "convergent constructive feedback" model introduced in our previous Herschel study., Accepted for publication in the Astrophysical Journal
Published: 2015
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10. Ram Pressure Stripping in the Virgo Cluster

Author: P. Salomé, Jonathan Braine, Kalliopi Dasyra, C. Verdugo, Francoise Combes, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Chaire Galaxies et cosmologie, Collège de France (CdF (institution)), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), and Collège de France - Chaire Galaxies et cosmologie
Subjects: Physics, galaxies: clusters: intracluster medium, Star formation, Molecular cloud, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Virgo Cluster, Astrophysics - Astrophysics of Galaxies, Galaxy, Ram pressure, Plume, Stars, Space and Planetary Science, Intracluster medium, Astrophysics of Galaxies (astro-ph.GA), galaxies: interactions, galaxies: clusters: individual: Virgo, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], galaxies: evolution, Astrophysics::Galaxy Astrophysics, galaxies: ISM
Abstract: International audience; Gas can be violently stripped from their galaxy disks in rich clusters, and be dispersed over 100kpc-scale tails or plumes. Young stars have been observed in these tails, suggesting they are formed in situ. This will contribute to the intracluster light, in addition to tidal stripping of old stars. We want to quantify the efficiency of intracluster star formation. We present CO(1--0) and CO(2--1) observations, made with the IRAM-30m telescope, towards the ram-pressure stripped tail northeast of NGC4388 in Virgo. HII regions found all along the tails, together with dust patches have been targeted. We detect molecular gas in 4 positions along the tail, with masses between 7x10$^5$ to 2x10$^6$ M$_\odot$. Given the large distance from the NGC 4388 galaxy, the molecular clouds must have formed in situ, from the HI gas plume. We compute the relation between surface densities of star formation and molecular gas in these regions, and find that the star formation has very low efficiency. The corresponding depletion time of the molecular gas can be up to 500 Gyr and more. Since this value exceeds a by far Hubble time, this gas will not be converted into stars, and will stay in a gaseous phase to join the intracluster medium.
Published: 2015
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11. ALMA observations of TiO$_2$ around VY Canis Majoris

Author: A. M. S. Richards, A. Baudry, E. O'Gorman, E. M. L. Humphreys, Sebastien Muller, Wouter Vlemmings, John H. Black, L. Decin, Matthias Maercker, E. De Beck, Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Terre et Environnement de Lorraine (OTELo), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Department of Biology, Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)-Institute of Cell Biology, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, circtunstellar matter, mass-loss [Stars], individual: VY Canis Majoris [Stars], Radiation field, FOS: Physical sciences, Astronomy and Astrophysics, stars [Submillimeter], Astrophysics, Circumstellar matter, Spectral line, Gas phase, Stars, Supergiants, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astronomy, Astrophysics and Cosmology, Red supergiant, Outflow, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Excitation, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: Titanium dioxide, TiO$_2$, is a refractory species that could play a crucial role in the dust-condensation sequence around oxygen-rich evolved stars. To date, gas phase TiO$_2$ has been detected only in the complex environment of the red supergiant VY CMa. We aim to constrain the distribution and excitation of TiO$_2$ around VY CMa in order to clarify its role in dust formation. We analyse spectra and channel maps for TiO$_2$ extracted from ALMA science verification data. We detect 15 transitions of TiO$_2$, and spatially resolve the emission for the first time. The maps demonstrate a highly clumpy, anisotropic outflow in which the TiO$_2$ emission likely traces gas exposed to the stellar radiation field. A roughly east-west oriented, accelerating bipolar-like structure is found, of which the blue component runs into and breaks up around a solid continuum component. A distinct tail to the south-west is seen for some transitions, consistent with features seen in the optical and near-infrared. We find that a significant fraction of TiO$_2$ remains in the gas phase outside the dust-formation zone and suggest that this species might play only a minor role in the dust-condensation process around extreme oxygen-rich evolved stars like VY CMa., Accepted for publication in Astronomy & Astrophysics, 25 pages, 20 figures
Published: 2015
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12. Understanding star formation in molecular clouds. II. Signatures of gravitational collapse of IRDCs

Author: Nicola Schneider, Christoph Federrath, Nicolas Peretto, Pascal Tremblin, Volker Ossenkopf, Robert Simon, Timea Csengeri, Sylvain Bontemps, Ralf S. Klessen, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Austrian Centre of Industrial Biotechnology GmbH (ACIB), Department of Chemistry, Organic and Bioorganic Chemistry, Karl-Franzens-Universität [Graz, Autriche], and University of Graz
Subjects: Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Turbulence, Infrared, Star formation, Molecular cloud, FOS: Physical sciences, Astronomy and Astrophysics, Probability density function, Astrophysics, 01 natural sciences, Power law, Astrophysics - Astrophysics of Galaxies, Stars, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Gravitational collapse, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, QB
Abstract: We analyse column density and temperature maps derived from Herschel dust continuum observations of a sample of massive infrared dark clouds (G11.11-0.12, G18.82-0.28, G28.37+0.07, G28.53-0.25). We disentangle the velocity structure of the clouds using 13CO 1-0 and 12CO 3-2 data, showing that these IRDCs are the densest regions in massive giant molecular clouds and not isolated features. The probability distribution function (PDF) of column densities for all clouds have a power-law distribution over all (high) column densities, regardless of the evolutionary stage of the cloud: G11.11-0.12, G18.82-0.28, and G28.37+0.07 contain (proto)-stars, while G28.53-0.25 shows no signs of star formation. This is in contrast to the purely log-normal PDFs reported for near/mid-IR extinction maps. We only find a log-normal distribution for lower column densities, if we perform PDFs of the column density maps of the whole GMC in which the IRDCs are embedded. By comparing the PDF slope and the radial column density profile, we attribute the power law to the effect of large-scale gravitational collapse and to local free-fall collapse of pre- and protostellar cores. Independent from the PDF analysis, we find infall signatures in the spectral profiles of 12CO for G28.37+0.07 and G11.11-0.12, supporting the scenario of gravitational collapse. IRDCs are the densest regions within GMCs, which may be the progenitors of massive stars or clusters. At least some of the IRDCs are probably the same features as ridges (high column density regions with N>1e23 cm-2 over small areas), which were defined for nearby IR-bright GMCs. Because IRDCs are only confined to the densest (gravity dominated) cloud regions, the PDF constructed from this kind of a clipped image does not represent the (turbulence dominated) low column density regime of the cloud., A&A in press
Published: 2015
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13. Understanding star formation in molecular clouds. I. Effects of line-of-sight contamination on the column density structure

Author: Volker Ossenkopf, Christoph Federrath, Timea Csengeri, Ph. André, Ralf S. Klessen, Philipp Girichidis, Nicola Schneider, Sylvain Bontemps, Pascal Tremblin, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), IRIN, and Université de Nantes (UN)
Subjects: Physics, Line-of-sight, AURIGA, Star formation, extinction, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Molecular cloud, FOS: Physical sciences, Astronomy and Astrophysics, Context (language use), Probability density function, Astrophysics, Astrophysics - Astrophysics of Galaxies, ISM: clouds, methods: data analysis, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Gravitational collapse, Log-normal distribution, submillimeter: ISM, dust, Astrophysics::Galaxy Astrophysics, ISM: general
Abstract: Column-density maps of molecular clouds are one of the most important observables in the context of molecular cloud- and star-formation (SF) studies. With the Herschel satellite it is now possible to determine the column density from dust emission. We use observations and simulations to demonstrate how LOS contamination affects the column density probability distribution function (PDF). We apply a first-order approximation (removing a constant level) to the molecular clouds of Auriga, Maddalena, Carina and NGC3603. In perfect agreement with the simulations, we find that the PDFs become broader, the peak shifts to lower column densities, and the power-law tail of the PDF flattens after correction. All PDFs have a lognormal part for low column densities with a peak at Av~2, a deviation point (DP) from the lognormal at Av(DP)~4-5, and a power-law tail for higher column densities. Assuming a density distribution rho~r^-alpha, the slopes of the power-law tails correspond to alpha(PDF)=1.8, 1.75, and 2.5 for Auriga, Carina, and NGC3603 (alpha~1.5-2 is consistent gravitational collapse). We find that low-mass and high-mass SF clouds display differences in the overall column density structure. Massive clouds assemble more gas in smaller cloud volumes than low-mass SF ones. However, for both cloud types, the transition of the PDF from lognormal shape into power-law tail is found at the same column density (at Av~4-5 mag). Low-mass and high-mass SF clouds then have the same low column density distribution, most likely dominated by supersonic turbulence. At higher column densities, collapse and external pressure can form the power-law tail. The relative importance of the two processes can vary between clouds and thus lead to the observed differences in PDF and column density structure., Comment: A&A accepted, 15.12. 2014
Published: 2015
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14. Water in star-forming regions with Herschel (WISH) (Corrigendum). V. The physical conditions in low-mass protostellar outflows revealed by multi-transition water observations

Author: I. San Jose-Garcia, T. A. van Kempen, Brunella Nisini, M. Tafalla, Joseph C. Mottram, Fabrice Herpin, Lars E. Kristensen, Friedrich Wyrowski, E. F. van Dishoeck, Ruud Visser, Edwin Bergin, Simon Bruderer, Paola Caselli, Arnold O. Benz, René Liseau, G. Santangelo, F. F. S. van der Tak, Doug Johnstone, Michiel R. Hogerheijde, Agata Karska, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Max-Planck-Institut für Extraterrestrische Physik (MPE), foreign laboratories (FL), CERN [Genève], Institute of Astronomy [ETH Zürich], Department of Physics [ETH Zürich] (D-PHYS), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Department of Astronomy [Ann Arbor], University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Natl Res Council Canada, Herzberg Inst Astrophys, Victoria, BC V9E 2E7 Canada, Natl Res Council Canada, Herzberg Inst Astrophys, Victoria, INAF - Osservatorio Astronomico di Roma (OAR), SRON Netherlands Institute for Space Research (SRON), and Max-Planck-Institut für Radioastronomie (MPIFR)
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Context (language use), Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Protostar, molecules, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, Line (formation), Physics, Jet (fluid), stars: formation, stars: formation – ISM: jets and outflows – ISM: molecules – stars: protostars – errata, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Accretion (meteorology), stars: protostars, Star formation, Astronomy and Astrophysics, ISM: jets and outflows, 13. Climate action, Space and Planetary Science, ISM, Outflow, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Low Mass, addenda, errata
Abstract: Context. Outflows are an important part of the star formation process as both the result of ongoing active accretion and one of the main sources of mechanical feedback on small scales. Water is the ideal tracer of these effects because it is present in high abundance for the conditions expected in various parts of the protostar, particularly the outflow. Aims. We constrain and quantify the physical conditions probed by water in the outflow-jet system for Class 0 and I sources. Methods. We present velocity-resolved Herschel HIFI spectra of multiple water-transitions observed towards 29 nearby Class 0/ Ip rotostars as part of the WISH guaranteed time key programme. The lines are decomposed into different Gaussian components, with each component related to one of three parts of the protostellar system; quiescent envelope, cavity shock and spot shocks in the jet and at the base of the outflow. We then use non-LTE radex models to constrain the excitation conditions present in the two outflow-related components. Results. Water emission at the source position is optically thick but effectively thin, with line ratios that do not vary with velocity, in contrast to CO. The physical conditions of the cavity and spot shocks are similar, with post-shock H2 densities of order 10 5 −10 8 cm −3 and H2O column densities of order 10 16 −10 18 cm −2 .H 2O emission originates in compact emitting regions: for the spot shocks these correspond to point sources with radii of order 10−200 AU, while for the cavity shocks these come from a thin layer along the outflow cavity wall with thickness of order 1−30 AU. Conclusions. Water emission at the source position traces two distinct kinematic components in the outflow; J shocks at the base of the outflow or in the jet, and C shocks in a thin layer in the cavity wall. The similarity of the physical conditions is in contrast to off-source determinations which show similar densities but lower column densities and larger filling factors. We propose that this is due to the differences in shock properties and geometry between these positions. Class I sources have similar excitation conditions to Class 0 sources, but generally smaller line-widths and emitting region sizes. We suggest that it is the velocity of the wind driving the outflow, rather than the decrease in envelope density or mass, that is the cause of the decrease in H2O intensity between Class 0 and I sources.
Published: 2015
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15. First detection of CF+ towards a high-mass protostar

Author: Timea Csengeri, S. Bontemps, Bertrand Lefloch, Nicola Schneider, F. Herpin, S. Fechtenbaum, Ana Duarte-Cabral, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Photon, Population, FOS: Physical sciences, Astrophysics, Dissociation (chemistry), outflows, Ion, Ionization, Protostar, education, Solar and Stellar Astrophysics (astro-ph.SR), QB, Physics, education.field_of_study, Photosphere, stars: individual: CygX-N63, stars: formation, stars: protostars, Astronomy and Astrophysics, stars: massive, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, stars: winds, Outflow, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We report the first detection of the J = 1 - 0 (102.6 GHz) rotational lines of CF+ (fluoromethylidynium ion) towards CygX-N63, a young and massive protostar of the Cygnus X region. This detection occurred as part of an unbiased spectral survey of this object in the 0.8-3 mm range, performed with the IRAM 30m telescope. The data were analyzed using a local thermodynamical equilibrium model (LTE model) and a population diagram in order to derive the column density. The line velocity (-4 km s-1) and line width (1.6 km s-1) indicate an origin from the collapsing envelope of the protostar. We obtain a CF+ column density of 4.10e11 cm-2. The CF+ ion is thought to be a good tracer for C+ and assuming a ratio of 10e-6 for CF+/C+, we derive a total number of C+ of 1.2x10e53 within the beam. There is no evidence of carbon ionization caused by an exterior source of UV photons suggesting that the protostar itself is the source of ionization. Ionization from the protostellar photosphere is not efficient enough. In contrast, X-ray ionization from the accretion shock(s) and UV ionization from outflow shocks could provide a large enough ionizing power to explain our CF+ detection. Surprisingly, CF+ has been detected towards a cold, massive protostar with no sign of an external photon dissociation region (PDR), which means that the only possibility is the existence of a significant inner source of C+. This is an important result that opens interesting perspectives to study the early development of ionized regions and to approach the issue of the evolution of the inner regions of collapsing envelopes of massive protostars. The existence of high energy radiations early in the evolution of massive protostars also has important implications for chemical evolution of dense collapsing gas and could trigger peculiar chemistry and early formation of a hot core., 6 pages
Published: 2015
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16. Water in Massive Young Stellar Objects Revealed by Herschel PACS Spectroscopy

Author: Kwon, Woojin, Tak, Floris, Agata Karska, Herczeg, Gregory, Chavarria, Luis, Herpin, Fabrice, Wyrowski, Friedrich, Braine, Jonathan, Dishoeck, Ewine, SRON Netherlands Institute for Space Research (SRON), foreign laboratories (FL), CERN [Genève], Kavli Institute for Astronomy and Astrophysics [Beijing] (KIAA-PKU), Peking University [Beijing], FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Max-Planck-Institut für Extraterrestrische Physik (MPE), and Kapteyn Astronomical Institute
Subjects: [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]
Abstract: International audience; Water has been found in various stages of star formation and plays a role as an efficient coolant. We have detected multiple water lines in the Herschel PACS imaging spectroscopy data toward ten massive young stellar objects taken as part of the WISH project. The ten targets include four high mass protostellar objects, two hot molecular cores, and four ultracompact HII regions. The water lines detected in our sample appear either in emission or in absorption depending on relative positions from the object center and wavelengths: absorption tends to appear in shorter wavelengths and/or toward central positions. We discuss the origin of water lines based on line flux spatial distributions, rotational temperature distributions, and line flux ratios, as well as compared to central heating envelope models. In addition, OH line results are addressed for whether they can be understood in the same manner of water.
Published: 2015

17. Warm Gas and Dust of Massive Young Stellar Objects Revealed by Herschel PACS Spectroscopy

Author: Kwon, Woojin, Tak, Floris, Agata Karska, Herczeg, Gregory, Chavarria, Luis, Herpin, Fabrice, Wyrowski, Friedrich, Braine, Jonathan, Dishoeck, Ewine, SRON Netherlands Institute for Space Research (SRON), foreign laboratories (FL), CERN [Genève], Kavli Institute for Astronomy and Astrophysics [Beijing] (KIAA-PKU), Peking University [Beijing], FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], and Max-Planck-Institut für Extraterrestrische Physik (MPE)
Subjects: [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]
Abstract: International audience; We present results of Herschel PACS imaging spectroscopy data toward ten massive young stellar objects taken as part of the WISH project. Our sample consists of four high mass protostellar objects (HMPOs), two hot molecular cores (HMCs), and four ultracompact HII regions (UCHIIs), and the spectra cover a broad range of wavelengths (55 to 210 micron) presenting various atomic and molecular lines as well as excellent continua. By fitting the continua utilizing a modified black-body formula we estimate mass-weighted temperature and column density distributions of warm dust and find that UCHII regions are hottest and HMCs are most deeply embedded. We also estimate rotational temperature and column density distributions of warm CO gas using the rotational diagram analysis. In addition, based on the comparison of high J CO line fluxes to the RATRAN estimates of central heating envelope models, we find that majority of warm CO is originated from bipolar outflow shocks.
Published: 2015

18. The Warm Dust Component in the S106 Region

Author: Adams, Joseph D., Terry Herter, Lau, Ryan M., Hora, Joseph L., Schneider, Nicola, Smith, Howard Alan, Guzman, Andres, Simon, Robert, Staguhn, Johannes, Hankins, Matt, Spitzer Cygnus-X Legacy Team, Herschel Cygnus-X Team, Department of Astronomy [Ithaca], Cornell University [New York], FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], AUTRES, General Practice, and Brighton and Sussex Medical School (BSMS)
Subjects: [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract: International audience; We present SOFIA/FORCAST images of S106 at the wavelengths 19, 25, 31, and 37 microns. We use these images to produce color temperature and optical depth maps in order to analyze the warm (~ 60 - 150 K) dust component. We resolve the disk shadow region into several relatively cool (~ 60 - 78 K) lanes with a radially dependent temperature gradient and warmer (~ 75 - 85 K) pockets of dust with a more uniform temperature distribution. The warmer pockets are spatially correlated with pockets of polycyclic aromatic hydrocarbon and HI emission as seen in the images presented by Smith et al. (2001). These results indicate that the disk is clumpy or contains holes with relatively higher UV throughput than the most obscuring parts. We also combine the SOFIA data with data from Spitzer/IRAC (3.6 - 8.0 microns), Herschel/PACS (70 and 160 microns), and the literature to produce the infrared spectral energy distributions of dust at locations in the disk shadow, bipolar lobes, compact sources, and the southwestern edge of the photodissociation region. From the SEDs and radiative transfer modeling, we constrain the mass abundances and size distributions of PAHs and dust grains such as silicates, carbonaceous grains, and very small, transiently heated grains, in these dramatically different regions.
Published: 2015

19. High mass star and cluster formation: new insights from Herschel

Author: Motte, Frederique, Bontemps, Sylvain, Hill, Tracey, Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: International audience; The HOBYS key program essentially imaged with Herschel all of the regions forming OB-type stars at distances less than 3 kpc from the Sun. This survey allows to statistically study the formation of 10-20 Msun stars and confirms that high-mass pre-stellar cores do not exist. HOBYS also reveals mini-starburst cloud ridges, which have high mean densities and are the privileged sites for the formation of high-mass stars.
Published: 2015

20. Measuring star formation with resolved observations: the test case of M 33

Author: P. van der Werf, S. D. Lord, Susanne Aalto, C. Kramer, Francoise Combes, D. Calzetti, Erik Rosolowsky, Frank P. Israel, Manolis Xilouris, S. Verley, J. Braine, M. Boquien, Gordon J. Stacey, V. Buat, Monica Relaño, A. Boselli, F. F. S. van der Tak, Fatemeh Tabatabaei, Department of Astronomy, University of Massachusetts System (UMASS), Istituto di Metodologie per l'Analisi Ambientale (IMAA), Consiglio Nazionale delle Ricerche [Potenza] (CNR), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Collège de France - Chaire Galaxies et cosmologie, Collège de France (CdF (institution)), California Institute of Technology (CALTECH), Dpto. Fisica Teorica y del Cosmos, Universidad de Granada = University of Granada (UGR), University of British Columbia (UBC), SRON Netherlands Institute for Space Research (SRON), Leiden Observatory [Leiden], Universiteit Leiden, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS Paris)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP), Universidad de Granada (UGR), Universiteit Leiden [Leiden], Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Kapteyn Astronomical Institute, École normale supérieure - Paris (ENS Paris), and Chaire Galaxies et cosmologie
Subjects: FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Scaling, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Star formation, Attenuation, Estimator, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, galaxies: individual: M 33, Galaxy, Redshift, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxies: star formation, Spatial ecology, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Monochromatic color, galaxies: ISM
Abstract: Context. Measuring star formation at a local scale is important to constrain star formation laws. Yet, it is not clear whether and how the measure of star formation is affected by the spatial scale at which a galaxy is observed. Aims. We want to understand the impact of the resolution on the determination of the spatially resolved star formation rate (SFR) and other directly associated physical parameters such as the attenuation. Methods. We have carried out a multi-scale, pixel-by-pixel study of the nearby galaxy M33. Assembling FUV, Halpha, 8, 24, 70, and 100 micron maps, we have systematically compared the emission in individual bands with various SFR estimators from a resolution of 33 pc to 2084 pc. Results. We have found that there are strong, scale-dependent, discrepancies up to a factor 3 between monochromatic SFR estimators and Halpha+24 micron. The scaling factors between individual IR bands and the SFR show a strong dependence on the spatial scale and on the intensity of star formation. Finally, strong variations of the differential reddening between the nebular emission and the stellar continuum are seen, depending on the specific SFR (sSFR) and on the resolution. At the finest spatial scales, there is little differential reddening at high sSFR. The differential reddening increases with decreasing sSFR. At the coarsest spatial scales the differential reddening is compatible with the canonical value found for starburst galaxies. Conclusions. Our results confirm that monochromatic estimators of the SFR are unreliable at scales smaller than 1 kpc. Furthermore, the extension of local calibrations to high redshift galaxies presents non-trivial challenges as the properties of these systems may be poorly known., 15 pages, 9 figures, 1 table. Accepted for publication in A&A
Published: 2015
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21. Molecular ions in the O-rich evolved star OH231.8+4.2: HCO$^+$,H$^{13}$CO$^+$ and first detection of SO$^+$, N$_2$H$^+$, and H$_3$O$^+$

Author: José Cernicharo, V. Bujarrabal, G. Quintana-Lacaci, Marcelino Agúndez, Friedrich Wyrowski, F. Herpin, L. Velilla Prieto, J. Alcolea, C. Sánchez Contreras, Javier R. Goicoechea, Karl M. Menten, Departamento de Astrofísica Molecular e Infrarroja (DAMIR), Instituto de Estructura de la Materia (IEM), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Instituto de RadioAstronomía Milimétrica (IRAM), Centre National de la Recherche Scientifique (CNRS), Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Radioastronomie (MPIFR), Ministerio de Ciencia e Innovación (España), and Ministerio de Economía y Competitividad (España)
Subjects: Astrochemistry, Analytical chemistry, FOS: Physical sciences, Excitation temperature, Astrophysics, Stars: late-type, 7. Clean energy, Spectral line, Ion, Radio lines: stars, Ionization, Bipolar outflow, winds, outflows [Stars], Stars: mass-loss, Emission spectrum, Solar and Stellar Astrophysics (astro-ph.SR), Physics, Nebula, mass-loss [Stars], stars [Radio lines], Stars: AGB and post-AGB, Astronomy and Astrophysics, AGB and post-AGB [Stars], Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, late-type [Stars], Stars: winds, outflows, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract: OH 231.8+4.2, a bipolar outflow around a Mira-type variable star, displays a unique molecular richness amongst circumstellar envelopes (CSEs) around O-rich AGB and post-AGB stars. We report line observations of the HCO+ and H13CO+ molecular ions and the first detection of SO+, N2H+, and (tentatively) H3O+ in this source. SO+ and H3O+ have not been detected before in CSEs around evolved stars. These data have been obtained as part of a full mm-wave and far-IR spectral line survey carried out with the IRAM 30 m radio telescope and with Herschel/HIFI. Except for H3O+, all the molecular ions detected in this work display emission lines with broad profiles (FWHM ~ 50−90 km s-1), which indicates that these ions are abundant in the fast bipolar outflow of OH 231.8. The narrow profile (FWHM ~ 14 km s-1) and high critical densities (>106 cm-3) of the H3O+ transitions observed are consistent with this ion arising from denser, inner (and presumably warmer) layers of the fossil remnant of the slow AGB CSE at the core of the nebula. From rotational diagram analysis, we deduce excitation temperatures of Tex~ 10−20 K for all ions except for H3O+, which is most consistent with Tex≈ 100 K. Although uncertain, the higher excitation temperature suspected for H3O+ is similar to that recently found for H2O and a few other molecules, which selectively trace a previously unidentified, warm nebular component. The column densities of the molecular ions reported here are in the range Ntot≈ [1−8] × 1013 cm-2, leading to beam-averaged fractional abundances relative to H2 of X(HCO+) ≈ 10-8, X(H13CO+) ≈2 × 10-9, X(SO+) ≈4 × 10-9, X(N2H+) ≈2 × 10-9, and X(H3O+) ≈7 × 10-9 cm-2. We have performed chemical kinetics models to investigate the formation of these ions in OH 231.8 as the result of standard gas phase reactions initiated by cosmic-ray and UV-photon ionization. The model predicts that HCO+, SO+, and H3O+ can form with abundances comparable to the observed average values in the external layers of the slow central core (at ~[3−8] × 1016 cm); H3O+ would also form quite abundantly in regions closer to the center (X(H3O+) ~ 10-9 at ~1016 cm). For N2H+, the model abundance is lower than the observed value by more than two orders of magnitude. The model fails to reproduce the abundance enrichment of HCO+, SO+, and N2H+ in the lobes, which is directly inferred from the broad emission profiles of these ions. Also, in disagreement with the narrow H3O+ spectra, the model predicts that this ion should form in relatively large, detectable amounts (≈10-9) in the external layers of the slow central core and in the high-velocity lobes. Some of the model-data discrepancies are reduced, but not suppressed, by lowering the water content and enhancing the elemental nitrogen abundance in the envelope. The remarkable chemistry of OH 231.8 probably reflects the molecular regeneration process within its envelope after the passage of fast shocks that accelerated and dissociated molecules in the AGB wind ~800 yr ago., This work has been partially supported by the Spanish MINECO through grants CSD2009-00038, AYA2009-07304, and AYA2012-32032.
Published: 2015
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22. Antifreeze in the hot core of Orion - First detection of ethylene glycol in Orion-KL

Author: X. H. Lu, N. Brouillet, Dominique Bockelée-Morvan, Alain Baudry, José Cernicharo, D. Despois, Nicolas Biver, Jacques Crovisier, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Departamento de Astrofísica Molecular e Infrarroja (DAMIR), Instituto de Estructura de la Materia (IEM), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Thermodynamic equilibrium, [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], FOS: Physical sciences, Astrophysics, 010402 general chemistry, 01 natural sciences, Molecular physics, chemistry.chemical_compound, Astrochemistry–ISM:molecules–Radiolines:ISM–ISM:individualobjects:Orion-KL–Comets:general, 0103 physical sciences, Molecule, 010303 astronomy & astrophysics, Conformational isomerism, Physics, Glycolaldehyde, Astronomy and Astrophysics, Rotational temperature, Astrophysics - Astrophysics of Galaxies, 3. Good health, 0104 chemical sciences, Interstellar medium, chemistry, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Antifreeze, Ethylene glycol
Abstract: Comparison of their chemical compositions shows, to first order, a good agreement between the cometary and interstellar abundances. However, a complex O-bearing organic molecule, ethylene glycol (CH$_{2}$OH)$_{2}$, seems to depart from this correlation because it was not easily detected in the interstellar medium although it proved to be rather abundant with respect to other O-bearing species in comet Hale-Bopp. Ethylene glycol thus appears, together with the related molecules glycolaldehyde CH$_{2}$OHCHO and ethanol CH$_{3}$CH$_{2}$OH, as a key species in the comparison of interstellar and cometary ices as well as in any discussion on the formation of cometary matter. We focus here on the analysis of ethylene glycol in the nearest and best studied hot core-like region, Orion-KL. We use ALMA interferometric data because high spatial resolution observations allow us to reduce the line confusion problem with respect to single-dish observations since different molecules are expected to exhibit different spatial distributions. Furthermore, a large spectral bandwidth is needed because many individual transitions are required to securely detect large organic molecules. Confusion and continuum subtraction are major issues and have been handled with care. We have detected the aGg' conformer of ethylene glycol in Orion-KL. The emission is compact and peaks towards the Hot Core close to the main continuum peak, about 2" to the south-west; this distribution is notably different from other O-bearing species. Assuming optically thin lines and local thermodynamic equilibrium, we derive a rotational temperature of 145 K and a column density of 4.6 10$^{15}$ cm$^{-2}$. The limit on the column density of the gGg' conformer is five times lower., Comment: 19 pages, 10 figures, A&A accepted
Published: 2015
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23. ATLASGAL - Kinematic distances and the dense gas mass distribution of the inner Galaxy

Author: B. S. Koribalski, D. Russeil, S. Bontemps, C. M. Walmsley, Leonardo Bronfman, James Urquhart, M. Wienen, Friedrich Wyrowski, Timea Csengeri, Frederic Schuller, Karl M. Menten, Max-Planck-Institut für Radioastronomie (MPIFR), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Departamento de Astronomia (DAS)
Subjects: Physics, Initial mass function, Mass distribution, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Star formation, Molecular cloud, FOS: Physical sciences, Velocity dispersion, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galactic plane, Astrophysics - Astrophysics of Galaxies, Galaxy, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), QB460, Protostar, Astrophysics::Earth and Planetary Astrophysics, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract: The formation of high mass stars and clusters occurs in giant molecular clouds. Objects in evolved stages of massive star formation such as protostars, hot molecular cores, and ultracompact HII regions have been studied in more detail than earlier, colder objects. With this in mind, the APEX Telescope Large Area Survey of the whole inner Galactic plane at 870 micron (ATLASGAL) has been carried out to provide a global view of cold dust and star formation at submillimetre wavelengths. To derive kinematic distances to a large sample of ATLASGAL clumps we divided them into groups of sources, which are located close together, mostly within a radius of 2 pc, and have velocities in a similar range with a median velocity dispersion of ~ 1 km/s. Using NH3, N2H+ and CS velocities we calculate near and far kinematic distances to 296 groups of ATLASGAL sources in the first quadrant and 393 groups in the fourth quadrant. We analyse HI self-absorption and HI absorption to resolve the kinematic distance ambiguity. We obtain a scale height of ~ 28+/-2 pc and displacement below the Galactic midplane of ~ -7+/-1 pc. Within distances from 2 to 18 kpc ATLASGAL clumps have a broad range of gas masses with a median of 1050 solar masses and a wide distribution of radii with a median of 0.4 pc. Their distribution in galactocentric radii is correlated with spiral arms. Using a statistically significant ATLASGAL sample we derive a power-law exponent of -2.2+/-0.1 of the clump mass function. This is consistent with the slope derived for clusters and with that of the stellar initial mass function. Examining the power-law index for different galactocentric distances and various source samples shows that it is independent of environment and evolutionary phase. Fitting the mass-size relationship by a power law gives a slope of 1.76+/-0.01 for cold sources such as IRDCs and warm clumps associated with HII regions., Comment: Figure 2 has a reduced file size, please see A&A version of this paper for high resolution graphics
Published: 2015
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24. Detection of two power-law tails in the probability distribution functions of massive GMCs

Author: Nicola Schneider, D. Russeil, S. Pezzuto, Frédérique Motte, Volker Ossenkopf, L. Spinoglio, M. Benedettini, S. Bontemps, Timea Csengeri, T. Rayner, Alain Abergel, J. Di Francesco, P. Didelon, Philipp Girichidis, L. D. Anderson, A. Rivera-Ingraham, Ralf S. Klessen, Matthew Joseph Griffin, Pascal Tremblin, T. Hill, A. Zavagno, D. Arzoumanian, Ph. André, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Universität zu Köln = University of Cologne, Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, School of Physics and Astronomy [Cardiff], Cardiff University, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), National Radio Astronomy Observatory [Green Bank] (NRAO), National Radio Astronomy Observatory (NRAO), Department of Physics and Astronomy [Morgantown], West Virginia University [Morgantown], Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Istituto Nazionale di Astrofisica (INAF), Max-Planck-Institut für Radioastronomie (MPIFR), NRC Herzberg Institute of Astrophysics, National Research Council of Canada (NRC), Joint ALMA Observatory (JAO), European Southern Observatory (ESO)-National Radio Astronomy Observatory (NRAO), Zentrum für Astronomie der Universität Heidelberg (ZAH), Universität Heidelberg [Heidelberg] = Heidelberg University, Operations Department (ESAC), European Space Astronomy Centre (ESAC), Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA), University of Exeter, ANR-11-BS56-0010,STARFICH,Vers une vision unifiée de la formation stellaire dans les galaxies : Origine de la structure filamentaire du milieu interstellaire, des cœurs pré-stellaires et des amas protostellaires vus avec Herschel(2011), European Project: 291294,EC:FP7:ERC,ERC-2011-ADG_20110209,ORISTARS(2012), Laboratoire d'Astrophysique de Bordeaux [Pessac] ( LAB ), Université de Bordeaux ( UB ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Bordeaux ( UB ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Procédés, Matériaux et Energie Solaire ( PROMES ), Université de Perpignan Via Domitia ( UPVD ) -Centre National de la Recherche Scientifique ( CNRS ), Institut d'astrophysique spatiale ( IAS ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), National Radio Astronomy Observatory [Green Bank] ( NRAO ), National Radio Astronomy Observatory ( NRAO ), School of Physics & Astronomy [Cardiff], Laboratoire d'Astrophysique de Marseille ( LAM ), Aix Marseille Université ( AMU ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National d'Etudes Spatiales ( CNES ) -Centre National de la Recherche Scientifique ( CNRS ), Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Maison de la Simulation (MDLS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES)
Subjects: Physics, dust extinction, Angular momentum, extinction, [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Extinction (astronomy), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Power law, Astrophysics - Astrophysics of Galaxies, ISM: clouds, Space and Planetary Science, [ SDU.ASTR.CO ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astrophysics of Galaxies (astro-ph.GA), Gravitational collapse, Log-normal distribution, Optical depth (astrophysics), Range (statistics), Probability distribution, clouds dust, ISM, Astrophysics::Galaxy Astrophysics
Abstract: We report the novel detection of complex high-column density tails in the probability distribution functions (PDFs) for three high-mass star-forming regions (CepOB3, MonR2, NGC6334), obtained from dust emission observed with Herschel. The low column density range can be fit with a lognormal distribution. A first power-law tail starts above an extinction (Av) of ~6-14. It has a slope of alpha=1.3-2 for the rho~r^-alpha profile for an equivalent density distribution (spherical or cylindrical geometry), and is thus consistent with free-fall gravitational collapse. Above Av~40, 60, and 140, we detect an excess that can be fitted by a flatter power law tail with alpha>2. It correlates with the central regions of the cloud (ridges/hubs) of size ~1 pc and densities above 10^4 cm^-3. This excess may be caused by physical processes that slow down collapse and reduce the flow of mass towards higher densities. Possible are: 1. rotation, which introduces an angular momentum barrier, 2. increasing optical depth and weaker cooling, 3. magnetic fields, 4. geometrical effects, and 5. protostellar feedback. The excess/second power-law tail is closely linked to high-mass star-formation though it does not imply a universal column density threshold for the formation of (high-mass) stars., MNRAS Letters, accepted 20.7.2015, in press
Published: 2015
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25. Formation of structures around HII regions: ionization feedback from massive stars

Author: Wolfgang Schmidt, Pascal Tremblin, Nicola Schneider, Edouard Audit, Vincent Minier, Finnish Meteorological Institute (FMI), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: ISM: kinematics and dynamics, Physics, Nebula, Equation of state, 010308 nuclear & particles physics, Star formation, Molecular cloud, Shell (structure), Astronomy, Astronomy and Astrophysics, Astrophysics, methods: data analysis, 01 natural sciences, methods: numerical, Stars, ISM: HII regions, ISM: globules, Space and Planetary Science, Ionization, 0103 physical sciences, Radiative transfer, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: We present a new model for the formation of dense clumps and pillars around HII regions based on shocks curvature at the interface between a HII region and a molecular cloud. UV radiation leads to the formation of an ionization front and of a shock ahead. The gas is compressed between them forming a dense shell at the interface. This shell may be curved due to initial interface or density modulation caused by the turbulence of the molecular cloud. Low curvature leads to instabilities in the shell that form dense clumps while sufficiently curved shells collapse on itself to form pillars. When turbulence is high compared to the ionized-gas pressure, bubbles of cold gas have sufficient kinetic energy to penetrate into the HII region and detach themselves from the parent cloud, forming cometary globules.Using computational simulations, we show that these new models are extremely efficient to form dense clumps and stable and growing elongated structures, pillars, in which star formation might occur (see Tremblin et al.2012a). The inclusion of turbulence in the model shows its importance in the formation of cometary globules (see Tremblin et al.2012b). Globally, the density enhancement in the simulations is of one or two orders of magnitude higher than the density enhancement of the classical “collect and collapse“ scenario. The code used for the simulation is the HERACLES code, that comprises hydrodynamics with various equation of state, radiative transfer, gravity, cooling and heating.Our recent observations with Herschel (see Schneider et al.2012a) and SOFIA (see Schneider et al.2012b) and additional Spitzer data archives revealed many more of these structures in regions where OB stars have already formed such as the Rosette Nebula, Cygnus X, M16 and Vela, suggesting that the UV radiation from massive stars plays an important role in their formation. We present a first comparison between the simulations described above and recent observations of these regions.
Published: 2015
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26. Searching for trans ethyl methyl ether in Orion KL

Author: A. López, Jean-Claude Guillemin, N. Brouillet, L. Kolesniková, José L. Alonso, Laurent Margulès, Belén Tercero, José Cernicharo, Roman A. Motiyenko, Ministerio de Ciencia e Innovación (España), European Research Council, Ministerio de Economía y Competitividad (España), Dpt. Astrofisica Molecular e Infrarroja, CSIS - IEM, Departamento de Astrofísica Molecular e Infrarroja (DAMIR), Instituto de Estructura de la Materia (IEM), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Universidad de Valladolid-CSIC, Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523 (PhLAM), Université de Lille-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences Chimiques de Rennes (ISCR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
Subjects: ISM: individual objects: Orion KL, individual objects (Orion KL), Spin states, [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Analytical chemistry, FOS: Physical sciences, Ether, Astrophysics, clouds, Surveys, ISM: clouds, ISM: abundances, Article, individual objects: Orion KL [ISM], chemistry.chemical_compound, surveys, Molecule, molecules, Radio lines: ISM, molecules [ISM], Line (formation), Physics, abundances [ISM], abundances, Astronomy and Astrophysics, Rotational temperature, Astrophysics - Astrophysics of Galaxies, ISM: molecules, ISM [Radio lines], chemistry, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), radio lines, clouds [ISM]
Abstract: We report on the tentative detection of $trans$ Ethyl Methyl Ether (tEME), $t-CH_3CH_2OCH_3$, through the identification of a large number of rotational lines from each one of the spin states of the molecule towards Orion KL. We also search for $gauche$-$trans$-n-propanol, $Gt-n-CH_3CH_2CH_2OH$, an isomer of tEME in the same source. We have identified lines of both species in the IRAM 30m line survey and in the ALMA Science Verification data. We have obtained ALMA maps to establish the spatial distribution of these species. Whereas tEME mainly arises from the compact ridge component of Orion, Gt-n-propanol appears at the emission peak of ethanol (south hot core). The derived column densities of these species at the location of their emission peaks are $\leq(4.0\pm0.8)\times10^{15} cm^{-2}$ and $\leq(1.0\pm0.2)\times10^{15} cm^{-2}$ for tEME and Gt-n-propanol, respectively. The rotational temperature is $\sim100 K$ for both molecules. We also provide maps of $CH_3OCOH$, $CH_3CH_2OCOH$, $CH_3OCH_3$, $CH_3OH$, and $CH_3CH_2OH$ to compare the distribution of these organic saturated O-bearing species containing methyl and ethyl groups in this region. Abundance ratios of related species and upper limits to the abundances of non-detected ethers are provided. We derive an abundance ratio $N(CH_3OCH_3)/N(tEME)\geq150$ in the compact ridge of Orion., Accepted in A&A Letters
Published: 2015
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27. Resolving the stellar activity of the Mira AB binary with ALMA

Author: Sofia Ramstedt, E. O'Gorman, Alain Baudry, Elizabeth Humphreys, Margarita Karovska, Wouter Vlemmings, Markus Wittkowski, Department of Biology, Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)-Institute of Cell Biology, European Southern Observatory (ESO), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Brightness, close [binaries], Continuum (design consultancy), FOS: Physical sciences, Flux, individual: Mira AB [stars], stars: AGB and post-AGB, Astrophysics, law.invention, law, stars: atmospheres, Astronomy, Astrophysics and Cosmology, Solar and Stellar Astrophysics (astro-ph.SR), Physics, atmospheres [stars], binaries: close, Spectral index, Astronomy and Astrophysics, AGB and post-AGB [stars], Wavelength, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, stars: individual: Mira AB, Brightness temperature, Millimeter, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Flare
Abstract: We present the size, shape and flux densities at millimeter continuum wavelengths, based on ALMA science verification observations in Band 3 (~94.6 GHz) and Band 6 (~228.7 GHz), from the binary Mira A (o Ceti) and Mira B. The Mira AB system has been observed with ALMA at a spatial resolution of down to ~25 mas. The extended atmosphere of Mira A and the wind around Mira B sources are resolved and we derive the size of Mira A and of the ionized region around Mira B. The spectral indices within Band 3 (between 89-100 GHz) and between Band 3 and Band 6 are also derived. The spectral index of Mira A is found to change from 1.71+-0.05 within Band 3 to 1.54+-0.04 between Band 3 and 6. The spectral index of Mira B is 1.3+-0.2 in Band 3, in good agreement with measurements at longer wavelengths. However it rises to 1.72+-0.11 between the bands. For the first time the extended atmosphere of a star is resolved at these frequencies and for Mira A the diameter is ~3.8x3.2 AU in Band 3 (with brightness temperature Tb~5300 K) and ~4.0x3.6 AU in Band 6 (Tb~2500 K). Additionally, a bright hotspot of ~0.4 AU and with Tb~10000 K is found on the stellar disc of Mira A. The size of the ionized region around the accretion disk of Mira B is found to be ~2.4 AU. The emission around Mira B is consistent with that from a partially ionized wind of gravitationally bound material from Mira A close to the accretion disk of Mira B. The Mira A atmosphere does not fully match predictions, with brightness temperatures in Band 3 significantly higher than expected, potentially due to shock heating. The hotspot is likely due to magnetic activity and could be related to the previously observed X-ray flare of Mira A., Comment: 5 pages, 3 figures, accepted for A&A letters, updated to accepted version April 18
Published: 2015
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28. Ethyl alcohol and sugar in comet C/2014Q2 (Lovejoy)

Author: Nicolas Biver, R. Moreno, Jacques Crovisier, Jérémie Boissier, Dominique Bockelée-Morvan, Aage Sandqvist, P. Colom, Dariusz C. Lis, Didier Despois, Stefanie N. Milam, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), NASA Goddard Space Flight Center (GSFC), and École normale supérieure - Paris (ENS-PSL)
Subjects: Solar System, Planetesimal, 010504 meteorology & atmospheric sciences, Astronomy, Comet, complex organic molecules, FOS: Physical sciences, Photochemistry, Protoplanetary disk, 01 natural sciences, Astrobiology, chemistry.chemical_compound, 0103 physical sciences, Protostar, comets, 010303 astronomy & astrophysics, Research Articles, 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Glycolaldehyde, Multidisciplinary, Star formation, SciAdv r-articles, chemistry, 13. Climate action, Methanol, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], space science, Astrophysics - Earth and Planetary Astrophysics, Research Article
Abstract: First detections of ethyl alcohol and glycolaldehyde in a comet provide new constraints on solar system chemical complexity., The presence of numerous complex organic molecules (COMs; defined as those containing six or more atoms) around protostars shows that star formation is accompanied by an increase of molecular complexity. These COMs may be part of the material from which planetesimals and, ultimately, planets formed. Comets represent some of the oldest and most primitive material in the solar system, including ices, and are thus our best window into the volatile composition of the solar protoplanetary disk. Molecules identified to be present in cometary ices include water, simple hydrocarbons, oxygen, sulfur, and nitrogen-bearing species, as well as a few COMs, such as ethylene glycol and glycine. We report the detection of 21 molecules in comet C/2014 Q2 (Lovejoy), including the first identification of ethyl alcohol (ethanol, C2H5OH) and the simplest monosaccharide sugar glycolaldehyde (CH2OHCHO) in a comet. The abundances of ethanol and glycolaldehyde, respectively 5 and 0.8% relative to methanol (0.12 and 0.02% relative to water), are somewhat higher than the values measured in solar-type protostars. Overall, the high abundance of COMs in cometary ices supports the formation through grain-surface reactions in the solar system protoplanetary disk.
Published: 2015
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29. Observations of water with Herschel/HIFI toward the high-mass protostar AFGL 2591

Author: Fabrice Herpin, Yunhee Choi, E. F. van Dishoeck, F. F. S. van der Tak, Friedrich Wyrowski, Center for Advanced Radiation Sources [University of Chicago] (CARS), University of Chicago, SRON Netherlands Institute for Space Research (SRON), Max-Planck-Institut für Extraterrestrische Physik (MPE), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Radioastronomie (MPIFR), and Kapteyn Astronomical Institute
Subjects: Physics, stars: formation, Mean kinetic temperature, Astrophysics of Galaxies, Star formation, Extinction (astronomy), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics - Astrophysics of Galaxies, ISM: molecules, ISM: abundances, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Radiative transfer, Protostar, Outflow, Absorption (logic), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ISM: individual objects: AFGL 2591, Envelope (waves)
Abstract: Water is a sensitive tracer of physical conditions in star-forming regions because of its large abundance variations between hot and cold regions. We use spectrally resolved observations of rotational lines of H$_2$O and its isotopologs with Herschel/HIFI to constrain the physical conditions of the water emitting region toward the high-mass protostar AFGL2591. We use analytical estimates and rotation diagrams to estimate T$_{ex}$ and column densities of H$_2$O of the envelope, the outflow, and a foreground cloud. Furthermore, we use the non-LTE radiative transfer code to estimate the temperature and volume density of the H$_2$O emitting gas. Assuming LTE, we estimate an T$_{ex}$ of 42 K and a column density of 2$\times$10$^{14}$ cm$^{-2}$ for the envelope and 45 K and 4$\times$10$^{13}$ cm$^{-2}$ for the outflow, in beams of 4" and 30", respectively. Non-LTE models indicate a kinetic temperature of 60-230 K and a volume density of 7$\times$10$^6$-10$^8$ cm$^{-3}$ for the envelope, and a kinetic temperature of 70-90 K and a gas density of 10$^7$-10$^8$ cm$^{-3}$ for the outflow. The o/p ratio of the foreground absorption is 1.9$\pm$0.4, suggesting a low temperature. In contrast, the o/p ratio seen in absorption by the outflow is 3.5$\pm$1.0, as expected for warm gas. The water abundance in the envelope is 10$^{-9}$, similar to the low values found for other high- and low-mass protostars, suggesting that this abundance is constant during the embedded phase of high-mass star formation. The water abundance in the outflow is 10$^{-10}$, which is 10$\times$ lower than in the envelope and in the outflows of high- and low-mass protostars. Since beam size effects can only increase this estimate by a factor of 2, we suggest that the water in the outflow is affected by dissociating UV radiation due to the low extinction in the outflow lobe., Comment: Accepted for publication in A&A
Published: 2015
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30. Possible link between the power spectrum of interstellar filaments and the origin of the prestellar core mass function

Author: Davide Elia, Stefano Pezzuto, Vera Konyves, Frédérique Motte, Y. Shimajiri, Bilal Ladjelate, J. Di Francesco, Ph. André, A. Roy, Nicola Schneider, Derek Ward-Thompson, Tracey Hill, M. Benedettini, P. Palmeirim, G. J. White, Eugenio Schisano, Nicolas Peretto, F. Louvet, Luigi Spinoglio, Doris Arzoumanian, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), School of Physics and Astronomy [Cardiff], Cardiff University, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Istituto Nazionale di Astrofisica (INAF), Department of Physics and Astronomy [Victoria], University of Victoria [Canada] (UVIC), Joint ALMA Observatory (JAO), National Radio Astronomy Observatory (NRAO)-European Southern Observatory (ESO), Departamento de Astronomía, Universidad de Chile, Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy [Preston], University of Central Lancashire [Preston] (UCLAN), Department of Physics and Astronomy [Milton Keynes], The Open University [Milton Keynes] (OU), ANR-11-BS56-0010,STARFICH,Vers une vision unifiée de la formation stellaire dans les galaxies : Origine de la structure filamentaire du milieu interstellaire, des cœurs pré-stellaires et des amas protostellaires vus avec Herschel(2011), European Project: 291294,EC:FP7:ERC,ERC-2011-ADG_20110209,ORISTARS(2012), European Southern Observatory (ESO)-National Radio Astronomy Observatory (NRAO), Universidad de Chile = University of Chile [Santiago] (UCHILE), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES)
Subjects: Initial mass function, Evolution, ISM: structure, Stars: formation, Characteristic indices, FOS: Physical sciences, F500, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Spectral line, Power spectrum, Compressible turbulence, Gravitation, Protein filament, Functions, Mass functions, QC, Astrophysics::Galaxy Astrophysics, Physics, Turbulence, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Molecular cloud, Gaussian-like distributions, Spectral density, Astronomy and Astrophysics, Empirical correlations, Astrophysics - Astrophysics of Galaxies, Stars, Spectrum analysis, Amplitude, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA)
Abstract: Two major features of the prestellar CMF are: 1) a broad peak below 1 Msun, presumably corresponding to a mean gravitational fragmentation scale, and 2) a characteristic power-law slope, very similar to the Salpeter slope of the stellar initial mass function (IMF) at the high-mass end. While recent Herschel observations have shown that the peak of the prestellar CMF is close to the thermal Jeans mass in marginally supercritical filaments, the origin of the power-law tail of the CMF/IMF at the high-mass end is less clear. Inutsuka (2001) proposed a theoretical scenario in which the origin of the power-law tail can be understood as resulting from the growth of an initial spectrum of density perturbations seeded along the long axis of filaments by interstellar turbulence. Here, we report the statistical properties of the line-mass fluctuations of filaments in nearby molecular clouds observed with Herschel using a 1-D power spectrum analysis. The observed filament power spectra were fitted by a power-law function $(P_{true}(s) \propto s^{\alpha})$ after removing the effect of beam convolution at small scales. A Gaussian-like distribution of power-spectrum slopes was found centered at -1.6, close to that of the one-dimensional velocity power spectrum generated by subsonic Kolomogorov turbulence (-1.67). An empirical correlation, $P^{0.5}(s_0) \propto ^{1.4 \pm 0.1} $, was also found between the amplitude of each filament power spectrum $P(s_0)$ and the mean column density along the filament $$. Finally, the dispersion of line-mass fluctuations along each filament $\sigma_{\rm M_{line}}$ was found to scale with the physical length $L$ of the filament, roughly as $\sigma_{M_{line}} \propto L^{0.7}$. Overall, our results are consistent with the suggestion that the bulk of the CMF/IMF results from the gravitational fragmentation of filaments., Comment: 10 pages, 12 figures, Accepted for publication in Astronomy and Astrophysics journal
Published: 2015
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31. Calibration of Star-Formation Rate Measurements Across the Electromagnetic Spectrum

Author: Ann Hornschemeier, H. Wu, P. Kroupa, Andreas Zezas, J. Braine, C. C. Popescu, B. Lehmer, V. Buat, J. Pflamm-Altenburg, Daniel A. Dale, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), NASA Goddard Space Flight Center (GSFC), Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel (CAU), Deptartment of Measurement and Information Systems [Budapest] (DMIS), and Budapest University of Technology and Economics [Budapest] (BME)
Subjects: Physics, Luminous infrared galaxy, Initial mass function, Star formation, stars: luminosity function, Stellar atmosphere, Astronomy and Astrophysics, galaxies: fundamental parameters, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxy, infrared: galaxies, Interstellar medium, X-rays: binaries, Star cluster, galaxies: star clusters, Space and Planetary Science, binaries (including multiple): close, mass function, ultraviolet: galaxies, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Stellar evolution, Astrophysics::Galaxy Astrophysics
Abstract: Star-formation is one of the main processes that shape galaxies, and together with black-hole accretion activity the two agents of energy production in galaxies. It is important on a range of scales from star clusters/OB associations to galaxy-wide and even group/cluster scales. Recently, studies of star-formation in sub-galactic and galaxy-wide scales have met significant advances owing to: (a) developments in the theory of stellar evolution, stellar atmospheres, and radiative transfer in the interstellar medium; (b) the availability of more sensitive and higher resolution data; and (c) observations in previously poorly charted wavebands (e.g. Ultraviolet, Infrared, and X-rays). These data allow us to study more galaxies at ever-increasing distances and nearby galaxies in greater detail, and different modes of star formation activity such as massive star formation and low level continuous star formation in a variety of environments. In this contribution we summarize recent results in the fields of multi-wavelength calibrations of star-formation rate indicators, the Stellar Initial Mass function, and radiative transfer and modeling of the Spectrale Energy Disrtributions of galaxies.
Published: 2012
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32. Dust emission from the atomic and molecular gas in M 33: a changing β

Author: Fatemeh Tabatabaei, Jonathan Braine, Manolis Xilouris, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), and Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, Stellar population, Metallicity, Milky Way, media_common.quotation_subject, ISM: Clouds, Astrophysics, 01 natural sciences, 0103 physical sciences, Emission spectrum, Galaxies: Local Group, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, media_common, Physics, Spiral galaxy, Astronomy, Astronomy and Astrophysics, Universe, Interstellar medium, Andromeda, Galaxies: ISM, Space and Planetary Science, Galaxies: Individual: M 33, [SDU]Sciences of the Universe [physics], [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract: We use the very recently completed high-resolution IRAM CO survey of M33 with the high-resolution HI observations (published by Gratier et al. 2010, A&A, 522, 3) and Herschel Far-IR and submillimeter mapping observations to study how the dust behaves in the molecular and atomic gas phases of the interstellar medium (ISM). M33 is a “young" object in that it is gas-rich with a young stellar population and low metallicity as compared to large spirals like the Milky Way or Andromeda. Nonetheless, it is very clearly a spiral galaxy with a thin and reasonably axisymmetric disk. As such, it can be viewed as a stepping stone towards less evolved objects like magellanic irregulars (including the LMC and SMC) and perhaps distant objects in the early universe. More specifically, we look for radial variations in the dust emission spectrum (β parameter) as well as comparing regions dominated by either H2 or HI. The grey-body emission spectrum flattens (lower β) with galactocentric distance and generally is flatter in the atomic medium as compared to the molecular gas.
Published: 2012
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33. New N-bearing species towards OH 231.8+4.2

Author: José Cernicharo, V. Bujarrabal, F. Herpin, Marcelino Agúndez, G. Quintana-Lacaci, Friedrich Wyrowski, L. Velilla Prieto, Karl M. Menten, J. Alcolea, C. Sánchez Contreras, Departamento de Astrofísica Molecular e Infrarroja (DAMIR), Instituto de Estructura de la Materia (IEM), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Instituto de RadioAstronomía Milimétrica (IRAM), Centre National de la Recherche Scientifique (CNRS), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Radioastronomie (MPIFR), Ministerio de Ciencia e Innovación (España), Ministerio de Economía y Competitividad (España), Universidad Complutense de Madrid, and European Research Council
Subjects: Astrochemistry, 010504 meteorology & atmospheric sciences, Line: identification, FOS: Physical sciences, Astrophysics, Molecular processes, 01 natural sciences, Abundance (ecology), 0103 physical sciences, Asymptotic giant branch, Molecule, identification [Line], 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Line (formation), Physics, Stars: AGB and post-AGB, Astronomy and Astrophysics, Circumstellar matter, AGB and post-AGB [Stars], Astrophysics - Astrophysics of Galaxies, Stars, Astrophysics - Solar and Stellar Astrophysics, Orders of magnitude (time), 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Chemical equilibrium, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Circumstellar envelopes (CSEs) around asymptotic giant branch (AGB) stars are the main sites of molecular formation. OH 231.8+4.2 is a well studied oxygen-rich CSE around an intermediate-mass evolved star that, in dramatic contrast to most AGB CSEs, displays bipolar molecular outflows accelerated up to ~400 km s-1. OH 231.8+4.2 also presents an exceptional molecular richness probably due to shock-induced chemical processes. We report the first detection in this source of four nitrogen-bearing species, HNCO, HNCS, HC3N, and NO, which have been observed with the IRAM-30 m radiotelescope in a sensitive mm-wavelength survey towards this target. HNCO and HNCS are also first detections in CSEs. The observed line profiles show that the emission arises in the massive (~0.6 M⊙) central component of the envelope, expanding with low velocities of Vexp~ 15–30 km s-1, and at the base of the fast lobes. The NO profiles (with FWHM~ 40–50 km s-1) are broader than those of HNCO, HNCS, and HC3N and, most importantly, broader than the line profiles of 13CO, which is a good mass tracer. This indicates that the NO abundance is enhanced in the fast lobes relative to the slow, central parts. From LTE and non-LTE excitation analysis, we estimate beam-average rotational temperatures of Trot~ 15–30 K (and, maybe, up to ~55 K for HC3N) and fractional abundances relative to H2 of X(HNCO) ~ [0.8–1] × 10-7, X(HNCS) ~ [0.9–1] × 10-8, X(HC3N) ~ [5–7] × 10-9, and X(NO) ~ [1–2] × 10-6. NO is, therefore, amongst the most abundant N-bearing species in OH 231.8+4.2. We performed thermodynamical chemical equilibrium and chemical kinetics models to investigate the formation of these N-bearing species in OH 231.8+4.2. The model underestimates the observed abundances for HNCO, HNCS, and HC3N by several orders of magnitude, which indicates that these molecules can hardly be products of standard UV-photon and/or cosmic-ray induced chemistry in OH 231.8+4.2 and that other processes (e.g. shocks) play a major role in their formation. For NO, the model abundance, ≈10-6, is compatible with the observed average value; however, the model fails to reproduce the NO abundance enhancement in the high-velocity lobes (relative to the slow core) inferred from the broad NO profiles. The new detections presented in this work corroborate the particularly rich chemistry of OH 231.8+4.2, which is likely to be profoundly influenced by shock-induced processes, as proposed in earlier works., We acknowledge the Spanish MICINN/MINECO for funding support through grants AYA2009-07304, AYA2012-32032, and the ASTROMOL Consolider project CSD2009-00038. L.V. acknowledges the Spanish MINECO for funding support through FPI2012 short stay programme (ref. EEBB-I-13-06211) and the Laboratoire D’Astrophysique de Bordeaux (LAB-CNRS) for hosting this stay under the supervision of Dr. Marcelino Agúndez. L.V. also acknowledges the support of the Universidad Complutense de Madrid through the Ph.D. programme. M.A. acknowledges the support from the European Research Council (ERC Grant 209622: E3 ARTHS).
Published: 2015
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34. ALMA observations of anisotropic dust mass loss in the inner circumstellar environment of the red supergiant VY Canis Majoris

Author: Graham M. Harper, Theo Khouri, Pierre Kervella, E. De Beck, Elizabeth Humphreys, Sebastien Muller, Anita M. S. Richards, Wouter Vlemmings, E. O'Gorman, Leen Decin, Alain Baudry, Department of Biology, Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)-Institute of Cell Biology, FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Low Energy Astrophysics (API, FNWI)
Subjects: Kinematics, Star (game theory), FOS: Physical sciences, 3-Dimensional Morphology, Astrophysics::Cosmology and Extragalactic Astrophysics, Late-Type Stars, Astrophysics, star winds, Convection, circumstellar matter, evolution, Emissivity, Astrophysics::Solar and Stellar Astrophysics, Astronomy, Astrophysics and Cosmology, Red supergiant, Submillimeter, Continuum (set theory), Anisotropy, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Convection cell, Physics, Spectral index, Mu-M, supergiants, Astronomy and Astrophysics, Line, Stars:supergiants-Stars:individual:VYCMa-Stars:mass-loss-Dust:stars, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], VY CMa, Stars, Astrophysics - Solar and Stellar Astrophysics, Evolved, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, star outflows, Extended Atmosphere
Abstract: The processes leading to dust formation and the subsequent role it plays in driving mass-loss in cool evolved stars is an area of intense study. Here, we present high resolution ALMA Science Verification data of the continuum emission around the highly evolved oxygen-rich red supergiant VY CMa. These data enable us to study the dust in its inner circumstellar environment at a spatial resolution of 129 mas at 321 GHz and 59 mas at 658 GHz, allowing us to trace dust on spatial scales down to 11 R$_{\star}$ (71 AU). Two prominent dust components are detected and resolved. The brightest dust component, C, is located 334 mas (61 R$_{\star}$) south-east of the star and has a dust mass of at least $2.5\times 10^{-4} $M$_{\odot}$. It has an emissivity spectral index of $\beta =-0.1$ at its peak, implying that it is either optically thick at these frequencies with a cool core of $T_{d}\lesssim 100$ K, and/or contains very large dust grains. Interestingly, not a single molecule in the ALMA data has emission close to the peak of this massive dust clump. The other main dust component, VY, is located at the position of the star and contains a total dust mass of $4.0 \times 10^{-5} $M$_{\odot}$. It also contains a weaker dust feature extending over $60 $R$_{\star}$ to the north with the total component having a typical emissivity spectral index of $\beta =0.7$. We find that $>17%$ of the dust mass around VY CMa is located in clumps ejected within a more quiescent roughly spherical stellar wind, with a quiescent dust mass loss rate of $5 \times 10^{-6}$ M$_{\odot} $yr$^{-1}$. The observations suggest a continuous preferentially directed mass-loss from the star over many decades and do not support current models of convective driven only mass loss in red supergiant stars. We thus suggest other forces, i.e., MHD disturbances, are also needed to explain the observations. ispartof: Astronomy & Astrophysics vol:573 pages:5- status: published
Published: 2014
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35. Herschel view of the large-scale structure in the Chamaeleon dark clouds

Author: Alves Oliveira, Catarina, Schneider, Nicola, Bruno Merín, Prusti, Timo, Ribas, Álvaro, Cox, Nick, Vavrek, Roland, Könyves, Vera, Arzoumanian, Doris, Puga, Elena, Pilbratt, Göran, Kóspal, Ágnes, André, Philippe, Didelon, Pierre, Men Shchikov, Alexander, Royer, Pierre, Waelkens, Christoffel, Bontemps, Sylvain, Winston, Elaine, European Space Astronomy Centre (ESAC), European Space Agency (ESA), FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Herschel Science Center [Madrid], European Space Agency (ESA)-European Space Agency (ESA), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), Instituut voor Sterrenkunde [Leuven], Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Leosphere, 76 rue Monceau, 75008 Paris, France
Subjects: [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]
Abstract: International audience; The Chamaeleon molecular cloud complex is one of the nearest star-forming sites and encompasses three molecular clouds (Cha I, II, and III) that have a different star-formation history, from quiescent (Cha III) to actively forming stars (Cha II), and one that reaches the end of star-formation (Cha I). In this contribution we will present the analysis of the column density and temperature maps derived from PACS and SPIRE observations from the Herschel Gould Belt Survey. We find that the column density maps reveal a different morphological appearance for each of the three clouds, with a ridge-like structure for Cha I, a clump-dominated regime for Cha II, and an intricate filamentary network for Cha III. The filament width is measured to be about 0.12±0.04 pc in the three clouds, and the filaments are found to be gravitationally unstable in Cha I and II, but mostly subcritical in Cha III. Faint filaments (striations) are prominent in Cha I and are mostly aligned with the large-scale magnetic field. The PDFs of all regions show a lognormal distribution at low column densities. For higher densities, the PDF of Cha I shows a turnover indicative of an extended higher density component and culminates in a power-law tail. Cha II shows a power-law tail with a slope characteristic of gravity. The PDF of Cha III can be best fit by a single lognormal. The turbulence properties of the three regions are found to be similar, pointing towards a scenario where the clouds are impacted by large-scale processes.

36. ALMA reveals VYCMa's sub-mm maser and dust distribution

Author: Richards, A. M. S., Impellizzeri, C. M. V., Humphreys, E. M., Vlahakis, C., Vlemmings, W., Baudry, Alain, de Beck, E., Decin, L., Etoka, S., Gray, M. D., Harper, G. M., Hunter, T. R., Kervella, P., Kerschbaum, F., Mcdonald, I., Melnick, G., Muller, S., Neufeld, D., O'Gorman, E., Parfenov, S. Yu., Peck, A. B., Shinnaga, H., Sobolev, A. M., Testi, L., Uscanga, L., Wootten, A., Yates, J. A., Zijlstra, A., FORMATION STELLAIRE 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Department of Biology, Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)-Institute of Cell Biology, Ural State University, European Southern Observatory (ESO), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Solar and Stellar Astrophysics, Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Galaxy Astrophysics
Abstract: Letter 4 pages, 7 figures plus appendix with 1 figure. Subitted to Astronomy and Astrophysics Letters 2014; Cool, evolved stars have copious, enriched winds. The structure of these winds and the way they are accelerated is not well known. We need to improve our understanding by studying the dynamics from the pulsating stellar surface to about 10 stellar radii, where radiation pressure on dust is fully effective. Some red supergiants have highly asymmetric nebulae, implicating additional forces. We retrieved ALMA Science Verification data providing images of sub-mm line and continuum emission from VY CMa. This enables us to locate water masers with milli-arcsec precision and resolve the dusty continuum. The 658-, 321- and 325-GHz masers lie in irregular, thick shells at increasing distances from the centre of expansion. For the first time this is confirmed as the stellar position, coinciding with a compact peak offset to the NW of the brightest continuum emission. The maser shells (and dust formation zone) overlap but avoid each other on tens-au scales. Their distribution is broadly consistent with excitation models but the conditions and kinematics appear to be complicated by wind collisions, clumping and asymmetries.

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