143 results on '"Bruderer, S."'
Search Results
2. A thorough QT study in the context of an uptitration regimen with selexipag, a selective oral prostacyclin receptor agonist
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Hoch M, Darpo B, Remenova T, Stoltz R, Zhou M, Kaufmann P, Bruderer S, and Dingemanse J
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Therapeutics. Pharmacology ,RM1-950 - Abstract
Matthias Hoch,1 Borje Darpo,2,3 Tatiana Remenova,4 Randall Stoltz,5 Meijian Zhou,2 Priska Kaufmann,1 Shirin Bruderer,1 Jasper Dingemanse1 1Department of Clinical Pharmacology, Actelion Pharmaceuticals Ltd, Allschwil, Switzerland; 2iCardiac Technologies Inc, Rochester, New York, NY, USA; 3Karolinska Institute, Department of Clinical Sciences, Danderyd’s Hospital, Division of Cardiovascular Medicine, Stockholm, Sweden; 4Drug Safety Department, Actelion Pharmaceuticals Ltd, Allschwil, Switzerland; 5Covance Clinical Research Unit, Evansville, IN, USA Abstract: The effects of selexipag and its active metabolite ACT-333679 on cardiac repolarization were assessed in a thorough QT study as per International Conference on Harmonisation E14 guidance. In this randomized, double-blind, placebo/positive-controlled, parallel-group study, healthy male and female subjects were randomized to receive escalating doses of selexipag (n=91) or placebo/moxifloxacin (n=68). Ascending multiple doses of selexipag in the range of 400-1,600 µg or placebo were administered twice daily for 21 days. Following a nested crossover design, subjects in the moxifloxacin/placebo treatment group received a single oral 400 mg dose of moxifloxacin on day 2 or 24. The primary endpoint (QT interval correction using individualized formula [QTcI]) was chosen based on a prospectively defined test applied to on-treatment data. The mean baseline-adjusted placebo-corrected ΔQTcI (ΔΔQTcI) for selexipag was small at all time points and never exceeded 1.4 msec (upper bound of 90% confidence interval [CI], 3.9 msec) on 800 µg or –0.7 msec (upper bound of 90% CI, 2.1 msec) on 1,600 µg. The mean ΔΔQTcI peak effect for moxifloxacin was 7.5 msec (lower bound of 90% CI, 4.8 msec). The exposure-response analysis did not demonstrate a relevant relationship between plasma concentrations of selexipag or ACT-333679 and ΔΔQTcI but, in contrast, a positive slope within the expected range for moxifloxacin. In conclusion, selexipag does not have an effect on cardiac repolarization. Keywords: prostacyclin, corrected QT, TQT, selexipag, moxifloxacin
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- 2014
3. Water in star-forming regions: Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
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van Dishoeck, E. F., Kristensen, L. E., Mottram, J. C., Benz, A. O., Bergin, E. A., Caselli, P., Herpin, F., Hogerheijde, M. R., Johnstone, D., Liseau, R., NISINI, Brunella, Tafalla, M., van der Tak, F. F. S., Wyrowski, F., Baudry, A., BENEDETTINI, Milena, Bjerkeli, P., Blake, G. A., Braine, J., Bruderer, S., Cabrit, S., Cernicharo, J., Choi, Y., Coutens, A., de Graauw, Th., Dominik, C., FEDELE , DAVIDE, Fich, M., Fuente, A., Furuya, K., Goicoechea, J. R., Harsono, D., Helmich, F. P., Herczeg, G. J., Jacq, T., Karska, A., Kaufman, M., Keto, E., Lamberts, T., Larsson, B., Leurini, Silvia, Lis, D. C., Melnick, G., Neufeld, D., Pagani, L., Persson, M., Shipman, R., TAQUET, VIANNEY DANIEL FRANCOIS, van Kempen, T. A., Walsh, C., Wampfler, S. F., Yıldız, U., WISH Team, Astronomy, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), and Low Energy Astrophysics (API, FNWI)
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Protoplanetary disks ,010504 meteorology & atmospheric sciences ,530 Physics ,Astrophysics - astrophysics of galaxies ,Stars: formation ,FOS: Physical sciences ,Astrophysics ,Astrophysics - Earth and planetary astrophysics ,01 natural sciences ,Luminosity ,0103 physical sciences ,Protostar ,Astrophysics::Solar and Stellar Astrophysics ,Spectroscopy ,010303 astronomy & astrophysics ,molecules [ISM] ,Physics::Atmospheric and Oceanic Physics ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences ,Line (formation) ,Astrochemistry ,Earth and Planetary Astrophysics (astro-ph.EP) ,Physics ,[PHYS]Physics [physics] ,Infrared: ISM ,formation [stars] ,astrochemistry ,jets and outflows [ISM] ,520 Astronomy ,protoplanetary disks ,Water gas ,ISM [infrared] ,Astronomy and Astrophysics ,ISM: molecules ,ISM: jets and outflows ,13. Climate action ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Excited state ,Outflow ,Astrophysics::Earth and Planetary Astrophysics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,Water vapor - Abstract
(abridged) Data and results from the WISH key program are summarized, designed to provide a legacy data set to address its physics and chemistry. WISH targeted ~80 sources along the two axes of luminosity and evolutionary stage: from low- to high-mass protostars and from pre-stellar cores to protoplanetary disks. Lines of H2O, HDO, OH, CO and [O I] were observed with the HIFI and PACS instruments, complemented by molecules that probe UV, X-ray or grain chemistry. Most of the far-infrared water emission from protostars is found to be compact, originating from warm outflowing and shocked gas at high density and temperature in at least two physical components. This gas is not probed by low-J CO lines, only by J>14. Water is a significant, but not dominant, coolant. Its abundance is universally low, of order H2O/H2=2E-6, pointing to shock and outflow cavity models that include UV radiation at 100-1000 times the ISRF. In cold quiescent pre-stellar cores and envelopes, the water abundance structure is accurately probed through velocity-resolved line profiles, confirming basic chemistry networks. The gaseous HDO/H2O ratio of 0.025, much higher than that of bulk ice, is representative of the outer photodesorbed ice layers and cold chemistry. Water abundances in the inner hot cores are high, but with variations from 5E-6 to 2E-4. Combined analyses of water gas and ice show that up to 50% of the oxygen budget may be missing, with possible explanations discussed. Water vapor emission from disks is weak, indicating that water ice is locked up in larger pebbles early on and that these pebbles have settled and drifted inward by the Class II stage. Quantitatively, many oceans of water ice are available. Extragalactic low-J H2O emission is mostly compact and collisionally excited. Prospects for future mid- to far-infrared missions are given., 58 pages, 39 figures, accepted for publication in A&A
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- 2021
4. Compact disks
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Miotello, A., Rosotti, G.P., Ansdell, M., Facchini, S., Manara, C.F., Williams, J.P., and Bruderer, S.
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Protoplanetary disks ,Submillimeter: planetary systems ,Astrophysics - Earth and planetary astrophysics ,Astrophysics - solar and stellar astrophysics - Published
- 2021
5. Incidence of and risk factors for severe hypoglycaemia in treated type 2 diabetes mellitus patients in the UK – a nested case–control analysis
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Bruderer, S. G., Bodmer, M., Jick, S. S., Bader, G., Schlienger, R. G., and Meier, C. R.
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- 2014
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6. INVESTIGATION OF PHARMACOKINETIC AND PHARMACODYNAMIC INTERACTIONS BETWEEN CLAZOSENTAN AND NIMODIPINE IN ASAH PATIENTS: A POPULATION ANALYSIS: P292
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Bruderer, S., Zisowsky, J., Fuseau, E., Gutierez, M., and Dingemanse, J.
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- 2011
7. Water in star-forming regions with Herschel(WISH)
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Benz, A. O., Bruderer, S., van Dishoeck, E. F., Melchior, M., Wampfler, S. F., van der Tak, F., Goicoechea, J. R., Indriolo, N., Kristensen, L. E., Lis, D. C., Mottram, J. C., Bergin, E. A., Caselli, P., Herpin, F., Hogerheijde, M. R., Johnstone, D., Liseau, R., Nisini, B., Tafalla, M., Visser, R., and Wyrowski, F.
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ISM ultraviolet ,ISM molecules ,Massive stars ,Astrophysics::High Energy Astrophysical Phenomena ,Star formation ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Low-mass stars ,Astrophysics::Galaxy Astrophysics ,Astrochemistry - Abstract
CONTEXT: Hydrides are simple compounds containing one or a few hydrogen atoms bonded to a heavier atom. They are fundamental precursor molecules in cosmic chemistry and many hydride ions have become observable in high quality for the first time thanks to the Herschel Space Observatory. Ionized hydrides such as CH⁺ and OH⁺ (and also HCO⁺), which affect the chemistry of molecules such as water, provide complementary information on irradiation by far-UV (FUV) or X-rays and gas temperature. AIMS: We explore hydrides of the most abundant heavier elements in an observational survey covering young stellar objects (YSOs) with different mass and evolutionary state. The focus is on hydrides associated with the dense protostellar envelope and outflows, contrary to previous work that focused on hydrides in diffuse foreground clouds. METHODS: Twelve YSOs were observed with HIFI on Herschel in six spectral settings providing fully velocity-resolved line profiles as part of the Water in star-forming regions with Herschel (WISH) program. The YSOs include objects of low (Class 0 and I), intermediate, and high mass, with luminosities ranging from 4 L⊙ to 2 × 105 L⊙. RESULTS: The targeted lines of CH⁺, OH⁺, H₂O⁺+, C⁺, and CH are detected mostly in blue-shifted absorption. H₃O⁺ and SH⁺ are detected in emission and only toward some high-mass objects. The observed line parameters and correlations suggest two different origins related to gas entrained by the outflows and to the circumstellar envelope. The derived column densities correlate with bolometric luminosity and envelope mass for all molecules, best for CH, CH⁺, and HCO⁺. The column density ratios of CH⁺/OH⁺ are estimated from chemical slab models, assuming that the H₂ density is given by the specific density model of each object at the beam radius. For the low-mass YSOs the observed ratio can be reproduced for an FUV flux of 2–400 times the interstellar radiation field (ISRF) at the location of the molecules. In two high-mass objects, the UV flux is 20–200 times the ISRF derived from absorption lines, and 300–600 ISRF using emission lines. Upper limits for the X-ray luminosity can be derived from H₃O⁺ observations for some low-mass objects. CONCLUSIONS: If the FUV flux required for low-mass objects originates at the central protostar, a substantial FUV luminosity, up to 1.5 L⊙, is required. There is no molecular evidence for X-ray induced chemistry in the low-mass objects on the observed scales of a few 1000 AU. For high-mass regions, the FUV flux required to produce the observed molecular ratios is smaller than the unattenuated flux expected from the central object(s) at the Herschel beam radius. This is consistent with an FUV flux reduced by circumstellar extinction or by bloating of the protostar.
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- 2016
8. VizieR Online Data Catalog: Spectra of CO and [CI] in protoplanetary disks (Kama+, 2016)
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Kama, M., Bruderer, S., Carney, M., Hogerheijde, M., van Dishoeck, E. F., Fedele, D., Baryshev, A., Boland, W., Gusten, R., Aikutalp, A., Choi, Y., Endo, A., Frieswijk, W., Karska, A., Klaassen, P., Koumpia, E., Kristensen, L., Leurini, S., Nagy, Z., Perez Beaupuits, J.-P., Risacher, C., van der Marel, N., van Kempen, T. A., van Weeren, R. J., Wyrowski, F., Yildiz, U. A., Astronomy, and Kapteyn Astronomical Institute
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YSOs ,Spectroscopy - Abstract
APEX CHAMP+ and FLASH spectra of CI 1-0, CI 2-1, and CO 6-5 towards protoplanetary disks. The data was delivered from the telescope in reduced form and is on the Ta (K) scale. Baselines have been subtracted with low-order (order 0,1,2) polynomials. Observations were carried out from 2008 through 2013, with typical on-source exposure times of 10-60 min. (2 data files).
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- 2016
9. HERSCHEL SURVEY OF GALACTIC OH + , H 2 O + , AND H 3 O + : PROBING THE MOLECULAR HYDROGEN FRACTION AND COSMIC-RAY IONIZATION RATE
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Iffrig, Olivier, Hennebelle, Patrick, Indriolo, Nick, Neufeld, D., Gerin, M., Schilke, P., Benz, A., Winkel, B., Menten, K., Chambers, E., Black, John, Bruderer, S., Falgarone, E., Godard, B., Goicoechea, J., Gupta, H., Lis, D., Ossenkopf, V., Persson, C., Sonnentrucker, P., Van Der Tak, F., Van Dishoeck, E., Wolfire, Mark, Wyrowski, F., 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'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), 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), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Radioastronomie (MPIFR), Onsala space observatory (oso), Chalmers University of Technology [Göteborg], Max-Planck-Institut für Extraterrestrische Physik (MPE), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris-Seine-Université Paris-Seine-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Consejo Superior de Investigaciones Científicas [Spain] (CSIC), Laboratoire Univers et Théories (LUTH (UMR_8102)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Department of Materials Science and Engineering, KTH (KTH), Department of Materials Science and Engineering, KTH, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], 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), Onsala Space Observatory (OSO), Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), National Aeronautics and Space Administration (US), Ministerio de Ciencia e Innovación (España), Ministerio de Economía y Competitividad (España), and Kapteyn Astronomical Institute
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Hydrogen ,Astrophysics::High Energy Astrophysical Phenomena ,Interstellar cloud ,Continuum (design consultancy) ,chemistry.chemical_element ,FOS: Physical sciences ,Cosmic ray ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Ion ,cosmic rays ,Ionization ,Disc ,Astrophysics::Galaxy Astrophysics ,ComputingMilieux_MISCELLANEOUS ,Physics ,[PHYS]Physics [physics] ,astrochemistry ,Galactic Center ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies ,chemistry ,13. Climate action ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Astrochemistry - cosmic rays ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] - Abstract
In diffuse interstellar clouds the chemistry that leads to the formation of the oxygen-bearing ions OH+, H2O+, and H3O+ begins with the ionization of atomic hydrogen by cosmic rays, and continues through subsequent hydrogen abstraction reactions involving H2. Given these reaction pathways, the observed abundances of these molecules are useful in constraining both the total cosmic-ray ionization rate of atomic hydrogen (ζH) and molecular hydrogen fraction ($f_{\rm H_2}$). We present observations targeting transitions of OH+, H2O+, and H3O+ made with the Herschel Space Observatory along 20 Galactic sight lines toward bright submillimeter continuum sources. Both OH+ and H2O+ are detected in absorption in multiple velocity components along every sight line, but H3O+ is only detected along 7 sight lines. From the molecular abundances we compute $f_{\rm H_2}$ in multiple distinct components along each line of sight, and find a Gaussian distribution with mean and standard deviation 0.042 ± 0.018. This confirms previous findings that OH+ and H2O+ primarily reside in gas with low H2 fractions. We also infer ζH throughout our sample, and find a lognormal distribution with mean log (ζH) = –15.75 (ζH = 1.78 × 10–16 s–1) and standard deviation 0.29 for gas within the Galactic disk, but outside of the Galactic center. This is in good agreement with the mean and distribution of cosmic-ray ionization rates previously inferred from H$_3^+$ observations. Ionization rates in the Galactic center tend to be 10-100 times larger than found in the Galactic disk, also in accord with prior studies., Support for this work was provided by NASA through an award issued by JPL/Caltech. N.I. and D.A.N. are funded by NASA Research Support Agreement No. 1393741 provided through JPL. J.R.G. thanks the Spanish MINECO for funding support under grants CSD2009-00038 and AYA2012- 32032.
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- 2015
10. Disentangling the jet emission from protostellar systems. The ALMA view of VLA1623* (Research note)
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Santangelo, G., Murillo, N.M., Nisini, B., Codella, C., Bruderer, S., Lai, S.-P., and Dishoeck, E.F. van
- Published
- 2015
11. Gas versus dust sizes of protoplanetary discs: effects of dust evolution.
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Trapman, L., Facchini, S., Hogerheijde, M. R., van Dishoeck, E. F., and Bruderer, S.
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DUST ,OPTICAL depth (Astrophysics) ,BIOLOGICAL evolution ,GRAIN growth ,ASTROCHEMISTRY ,PROTOPLANETARY disks - Abstract
Context. The extent of the gas in protoplanetary discs is observed to be universally larger than the extent of the dust. This is often attributed to radial drift and grain growth of the millimetre grains, but line optical depth produces a similar observational signature. Aims. We investigate in which parts of the disc structure parameter space dust evolution and line optical depth are the dominant drivers of the observed gas and dust size difference. Methods. Using the thermochemical model DALI with dust evolution included we ran a grid of models aimed at reproducing the observed gas and dust size dichotomy. Results. The relation between R
dust and dust evolution is non-monotonic and depends on the disc structure. The quantity Rgas is directly related to the radius where the CO column density drops below 1015 cm−2 and CO becomes photodissociated; Rgas is not affected by dust evolution but scales with the total CO content of the disc. While these cases are rare in current observations, Rgas /Rdust > 4 is a clear sign of dust evolution and radial drift in discs. For discs with a smaller Rgas /Rdust , identifying dust evolution from Rgas /Rdust requires modelling the disc structure including the total CO content. To minimize the uncertainties due to observational factors requires FWHMbeam < 1× the characteristic radius and a peak S/N > 10 on the12 CO emission moment zero map. For the dust outer radius to enclose most of the disc mass, it should be defined using a high fraction (90–95%) of the total flux. For the gas, any radius enclosing >60% of the12 CO flux contains most of the disc mass. Conclusions. To distinguish radial drift and grain growth from line optical depth effects based on size ratios requires discs to be observed at high enough angular resolution and the disc structure should to be modelled to account for the total CO content of the disc. [ABSTRACT FROM AUTHOR]- Published
- 2019
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12. Probing the protoplanetary disk gas surface density distribution with 13CO emission.
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Miotello, A., Facchini, S., van Dishoeck, E. F., and Bruderer, S.
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CARBON dioxide mitigation ,PROTOPLANETARY disks ,PLANETS ,ASTRONOMICAL observations ,LIGHT curves - Abstract
Context. How protoplanetary disks evolve is still an unsolved problem where different processes may be involved. Depending on the process, the disk gas surface density distribution Σ
gas may be very different and this could have diverse implications for planet formation. Together with the total disk mass, it is key to constrain Σgas as function of disk radius R from observational measurements. Aims. In this work we investigate whether spatially resolved observations of rarer CO isotopologues, such as13 CO, may be good tracers of the gas surface density distribution in disks. Methods. Physical-chemical disk models with different input Σgas (R) were run, taking into account CO freeze-out and isotope-selective photodissociation. The input disk surface density profiles were compared with the simulated13 CO intensity radial profiles to check whether and where the two follow each other. Results. For each combination of disk parameters, there is always an intermediate region in the disk where the slope of the13 CO radial emission profile and Σgas (R) coincide. In the inner part of the disk, the line radial profile underestimates Σgas , as13 CO emission becomes optically thick. The same happens at large radii where the column densities become too low and13 CO is not able to efficiently self-shield. Moreover, the disk becomes too cold and a considerable fraction of13 CO is frozen out, thus it does not contribute to the line emission. If the gas surface density profile is a simple power-law of the radius, the input power-law index can be retrieved within a ~20% uncertainty if one choses the proper radial range. If instead Σgas (R) follows the self-similar solution for a viscously evolving disk, retrieving the input power-law index becomes challenging, in particular for small disks. Nevertheless, we find that the power-law index γ can be in any case reliably fitted at a given line intensity contour around 6 K km s−1 , and this produces a practical method to constrain the slope of Σgas (R). Application of such a method is shown in the case study of the TW Hya disk. Conclusions. Spatially resolved13 CO line radial profiles are promising to probe the disk surface density distribution, as they directly trace Σgas (R) profile at radii well resolvable by ALMA. There, chemical processes like freeze-out and isotope-selective photodissociation do not affect the emission, and, assuming that the volatile carbon does not change with radius, no chemical model is needed when interpreting the observations. [ABSTRACT FROM AUTHOR]- Published
- 2018
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13. Excited OH^+, H_2O^+, and H_3O^+ in NGC 4418 and Arp 220
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González-Alfonso, E., Fischer, J., Bruderer, S., Müller, H. S. P., Graciá-Carpio, J., Sturm, E., Lutz, D., Poglitsch, A., Feuchtgruber, H., Veilleux, S., Contursi, A., Sternberg, A., Hailey-Dunsheath, S., Verma, A., Christopher, N., Davies, R., Genzel, R., and Tacconi, L.
- Abstract
We report on Herschel/PACS observations of absorption lines of OH^+, H_2O^+ and H_3O^+ in NGC 4418 and Arp 220. Excited lines of OH^+ and H_2O^+ with E_(lower) of at least 285 and ~200 K, respectively, are detected in both sources, indicating radiative pumping and location in the high radiation density environment of the nuclear regions. Abundance ratios OH^+/H_2O^+ of 1−2.5 are estimated in the nuclei of both sources. The inferred OH^+ column and abundance relative to H nuclei are (0.5−1) × 10^(16) cm^(-2) and ~ 2 × 10^(-8), respectively. Additionally, in Arp 220, an extended low excitation component around the nuclear region is found to have OH^+/H^2O^+ ~ 5−10. H_3O^+ is detected in both sources with N(H_3O^+) ~ (0.5−2) × 10^(16) cm^(-2), and in Arp 220 the pure inversion, metastable lines indicate a high rotational temperature of ~500 K, indicative of formation pumping and/or hot gas. Simple chemical models favor an ionization sequence dominated by H^+ → O^+ → OH^+ → H_2O^+ → H_3O^+, and we also argue that the H^+ production is most likely dominated by X-ray/cosmic ray ionization. The full set of observations and models leads us to propose that the molecular ions arise in a relatively low density (≳10^4 cm^(-3)) interclump medium, in which case the ionization rate per H nucleus (including secondary ionizations) is ζ > 10^(-13) s^(-1), a lower limit that is several × 10^2 times the highest current rate estimates for Galactic regions. In Arp 220, our lower limit for ζ is compatible with estimates for the cosmic ray energy density inferred previously from the supernova rate and synchrotron radio emission, and also with the expected ionization rate produced by X-rays. In NGC 4418, we argue that X-ray ionization due to an active galactic nucleus is responsible for the molecular ion production.
- Published
- 2013
14. The extremely truncated circumstellar disc of V410 X-ray 1: a precursor to TRAPPIST-1?
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Boneberg, D. M., Facchini, S., Clarke, C. J., Ilee, J. D., Booth, R. A., and Bruderer, S.
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PROTOPLANETARY disks ,CIRCUMSTELLAR matter ,TRAPPIST-1 ,BROWN dwarf stars ,SPECTRAL energy distribution ,DYNAMICAL systems - Abstract
Protoplanetary discs around brown dwarfs and very low mass (VLM) stars offer some of the best prospects for forming Earth-sized planets in their habitable zones. To this end, we study the nature of the disc around the VLM star V410 X-ray 1, whose spectral energy distribution (SED) is indicative of an optically thick and very truncated dust disc, with our modelling suggesting an outer radius of only 0.6 au. We investigate two scenarios that could lead to such a truncation, and find that the observed SED is compatible with both. The first scenario involves the truncation of both the dust and gas in the disc, perhaps due to a previous dynamical interaction or the presence of an undetected companion. The second scenario involves the fact that a radial location of 0.6 au is close to the expected location of the H
2 O snowline in the disc. As such, a combination of efficient dust growth, radial migration, and subsequent fragmentation within the snowline leads to an optically thick inner dust disc and larger, optically thin outer dust disc. We find that a firm measurement of the CO J = 2-1 line flux would enable us to distinguish between these two scenarios, by enabling a measurement of the radial extent of gas in the disc. Many models we consider contain at least several Earth-masses of dust interior to 0.6 au, suggesting that V410 X-ray 1 could be a precursor to a system with tightly packed inner planets, such as TRAPPIST-1. [ABSTRACT FROM AUTHOR]- Published
- 2018
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15. 'EX LUPI FROM QUIESCENCE TO OUTBURST: EXPLORING THE LTE APPROACH IN MODELING BLENDED H2O AND OH MID-INFRARED EMISSION' (vol 745, pg 90, 2012)
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Banzatti, A., Meyer, M. R., Bruderer, S., Geers, V., Pascucci, I., Lahuis, F., Juhasz, A., Henning, T., and Abraham, P.
- Published
- 2012
16. First hyperfine structure resolved OH FIR spectrum of a star-forming region
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Wampfler, S. F., Bruderer, S., Kristensen, L. E., Bergin, E. A., Benz, A. O., van Dishoeck, E. F., Herczeg, G. J., van der Tak, F. F. S., Goicoechea, J. R., Doty, S. D., Herpin, F., and Astronomy
- Abstract
Embedded protostars interact with their natal cloud through shocks and irradiation. The ambient interstellar medium warms up, allowing icy grain mantles to evaporate and making different chemical routes in the gas phase available. Water then becomes one of the most abundant molecular species in the gas phase. The Herschel key program `Water in Star-Forming Regions with Herschel (WISH)' studies the excitation and chemistry of water around protostars. Hydroxyl (OH) is of the cornerstone species in the water chemistry network, because it is closely linked to both the formation and destruction of water through the OH + H2 leftrightarrow H2O + H reactions and photodissociation processes. This poster presents the first OH observation with resolved hyperfine structure at 163 μm of a star-forming region obtained using HIFI on Herschel. The OH triplet from the high-mass star-forming region W3 IRS5 is in emission, with the line profile revealing a narrow component on top of a broad feature. The broad component is attributed to outflow emission based on comparison with molecular lines of other species, whereas the narrow component is in agreement with radiative transfer results for a spherically symmetric envelope model. The resolved hyperfine structure allows us to constrain the excitation temperature and the OH column density in our models simultaneously. The derived OH/H2O ratios in the envelope are consistent with the current picture of the water chemistry. In the outer envelope (T 100 K), water is efficiently formed from OH and the OH/H2O ratio is therefore expected to drop significantly, which is consistent with the derived value of the order of 10-4. For the outflow, a lower limit of OH/H2O > 0.025 is obtained and can be explained with either a fast J-type shock or a slower UV irradiated C-type shock.
- Published
- 2011
17. First hyperfine structure resolved OH FIR spectrum of a star-forming region
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S. F., Wampfler, BRUDERER, S., L. E., Kristensen, E. A., Bergin, A. O., Benz, DISHOECK E. F., Van, G. J., Herczeg, DER TAK F. F. S., Van, J. R., Goicoechea, S. D., Doty, HERPIN, Fabrice, Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1, 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), and Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB)
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[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] ,[PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] - Abstract
International audience; Embedded protostars interact with their natal cloud through shocks and irradiation. The ambient interstellar medium warms up, allowing icy grain mantles to evaporate and making different chemical routes in the gas phase available. Water then becomes one of the most abundant molecular species in the gas phase. The Herschel key program 'Water in Star-Forming Regions with Herschel (WISH)' studies the excitation and chemistry of water around protostars. Hydroxyl (OH) is of the cornerstone species in the water chemistry network, because it is closely linked to both the formation and destruction of water through the OH + H2 leftrightarrow H2O + H reactions and photodissociation processes. This poster presents the first OH observation with resolved hyperfine structure at 163 μm of a star-forming region obtained using HIFI on Herschel. The OH triplet from the high-mass star-forming region W3 IRS5 is in emission, with the line profile revealing a narrow component on top of a broad feature. The broad component is attributed to outflow emission based on comparison with molecular lines of other species, whereas the narrow component is in agreement with radiative transfer results for a spherically symmetric envelope model. The resolved hyperfine structure allows us to constrain the excitation temperature and the OH column density in our models simultaneously. The derived OH/H2O ratios in the envelope are consistent with the current picture of the water chemistry. In the outer envelope (T < 100 K), where OH and H2O are released into the gas phase by photodesorption from the ice mantles of dust grains, we find a ratio of about unity. Laboratory work by Öberg et al. (2009) demonstrated that similar amounts of OH and water are released with an expected OH/H2O ratio of 0.5-1. This ratio is also in agreement with the theoretical work by Andersson & van Dishoeck (2008). In the inner envelope (T > 100 K), water is efficiently formed from OH and the OH/H2O ratio is therefore expected to drop significantly, which is consistent with the derived value of the order of 10-4. For the outflow, a lower limit of OH/H2O > 0.025 is obtained and can be explained with either a fast J-type shock or a slower UV irradiated C-type shock.
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- 2011
18. The WADI key project: New insights to photon-dominated regions from Herschel observations
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Ossenkopf, V., Röllig, M., Kramer, C., Okada, Y., Fuente, A., Akyilmaz Yabaci, M., Benz, A. O., Berné, O., Boulanger, F., Bruderer, S., Dedes, C., France, K., Gerin, M., Goicoechea, J. R., Gusdorf, A., Güsten, R., Harris, A., Joblin, C., Klein, T., Latter, W., Le Petit, F., Lord, S., Martin, P. G., Pilleri, P., Martin-Pintado, J., Mookerjea, B., Neufeld, D. A., Phillips, T., Rizzo, R., Simon, R., Stutzki, J., van der Tak, F. F. S., Teyssier, D., Yorke, H., Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Physikalisches Institut [Köln], Universität zu Köln, Instituto de RadioAstronomía Milimétrica (IRAM), Centre National de la Recherche Scientifique (CNRS), foreign laboratories (FL), CERN [Genève], Observatorio Astronómico Nacional (OAN), oan, Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), 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)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-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 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), Max-Planck-Institut für Extraterrestrische Physik (MPE), 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), Center for Astrophysics and Space Astronomy [Boulder] (CASA), University of Colorado [Boulder], Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), 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), Division for Submm Technologies, Max-Planck-Institut für Radioastronomie (MPIFR), CRUK Medical Oncology Unit, The Churchill Hospital, Univ Toulouse UPS, Ctr Etud Spatiale Rayonnements, F-31062 Toulouse 9, France, Centre Etud Spatiale Rayonnements Toulouse, Los Alamos National Laboratory (LANL), KOSMA, I. Physikalisches Institut, Department of Child and Adolescent Neurology and Psychiatry, Catania University, Helmholtz zentrum für Schwerionenforschung GmbH (GSI), European Space Astronomy Centre (ESAC), European Space Agency (ESA), Röllig, M. and Simon, R. and Ossenkopf, V. and Stutzki, J., 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), Universität zu Köln = University of Cologne, Observatorio Astronomico Nacional, Madrid, 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), 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), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Università degli studi di Catania = University of Catania (Unict), Agence Spatiale Européenne = European Space Agency (ESA), Astronomy, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), 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), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich)-Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich), PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP), 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, Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)
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Physics ,geography ,geography.geographical_feature_category ,Photon ,Molecular cloud ,General Engineering ,Energy balance ,Measure (physics) ,Astronomy ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,13. Climate action ,Space and Planetary Science ,0103 physical sciences ,Key (cryptography) ,010306 general physics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Wadi ,ComputingMilieux_MISCELLANEOUS - Abstract
Within the Herschel key project "The Warm And Dense ISM" (WADI) we systematically observe a number of prominent photon-dominated regions (PDRs) to measure the impact of varying UV fields on the energy balance, the chemical and dynamical structure of heated molecular clouds.
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- 2011
19. Sensitive limits on the abundance of cold water vapor in the DM Tauri protoplanetary disk [Letter]
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Bergin, E. A., Hogerheijde, M. R., Brinch, C., Fogel, J., Yildiz, U. A., Kristensen, L. E., van Dishoeck, E. F., Bell, T. A., Blake, G. A., Cernicharo, J., Dominik, C., Lis, D., Melnick, G., Neufeld, D., Panic, O., Pearson, J. C., Bachiller, R., Baudry, A., Benedettini, M., Benz, A. O., Bjerkeli, P., Bontemps, S., Braine, J., Bruderer, S., Caselli, P., Codella, C., Daniel, F., di Giorgio, A. M., Doty, S. D., Encrenaz, P., Fich, M., Fuente, A., Giannini, T., Goicoechea, J. R., de Graauw, Th, Helmich, F., Herczeg, G. J., Herpin, F., Jacq, T., Johnstone, D., Jorgensen, J. K., Larsson, B., Liseau, R., Marseille, M., Mc Coey, C., Nisini, B., Olberg, M., Parise, Berengere, Plume, R., Risacher, C., Santiago-Garcia, J., Saraceno, P., Shipman, R., Tafalla, M., van Kempen, T. A., Visser, R., Wampfler, S. F., Wyrowski, F., van der Tak, F., Jellema, W., Tielens, A. G. G. M., Hartogh, P., Stuetzki, J., and Szczerba, R.
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QB - Abstract
We performed a sensitive search for the ground-state emission lines of ortho- and para-water vapor in the DM Tau protoplanetary disk using the Herschel/HIFI instrument. No strong lines are detected down to 3σ levels in 0.5 km s-1 channels of 4.2 mK for the 110–101 line and 12.6 mK for the 111–000 line. We report a very tentative detection, however, of the 110–101 line in the wide band spectrometer, with a strength of Tmb = 2.7 mK, a width of 5.6 km s-1 and an integrated intensity of 16.0 mK km s-1. The latter constitutes a 6σ detection. Regardless of the reality of this tentative detection, model calculations indicate that our sensitive limits on the line strengths preclude efficient desorption of water in the UV illuminated regions of the disk. We hypothesize that more than 95–99% of the water ice is locked up in coagulated grains that have settled to the midplane.
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- 2010
20. Water vapor toward starless cores: The Herschel view [Letter]
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Caselli, P., Keto, E., Pagani, L., Aikawa, Y., Yildiz, U. A., van der Tak, F. F. S., Tafalla, M., Bergin, E. A., Nisini, B., Codella, C., van Dishoeck, E. F., Bachiller, R., Baudry, A., Benedettini, M., Benz, A. O., Bjerkeli, P., Blake, G. A., Bontemps, S., Braine, J., Bruderer, S., Cernicharo, J., Daniel, F., di Giorgio, A. M., Dominik, C., Doty, S. D., Encrenaz, P., Fich, M., Fuente, A., Gaier, T., Giannini, T., Goicoechea, J. R., de Graauw, Th., Helmich, F., Herczeg, G. J., Herpin, F., Hogerheijde, M. R., Jackson, B., Jacq, T., Javadi, H., Johnstone, D., Jorgensen, J. K., Kester, D., Kristensen, L. E., Laauwen, W., Larsson, B., Lis, D., Liseau, R., Luinge, W., Marseille, M., McCoey, C., Megej, A., Melnick, G., Neufeld, D., Olberg, M., Parise, Berengere, Pearson, J. C., Plume, R., Risacher, C., Santiago-Garcia, J., Saraceno, P., Shipman, R., Siegel, P., van Kempen, T. A., Visser, R., Wampfler, S. F., and Wyrowski, F.
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QB - Abstract
Aims. Previous studies by the satellites SWAS and Odin provided stringent upper limits on the gas phase water abundance of dark clouds (x(H2O) < 7 × 10-9). We investigate the chemistry of water vapor in starless cores beyond the previous upper limits using the highly improved angular resolution and sensitivity of Herschel and measure the abundance of water vapor during evolutionary stages just preceding star formation.\ud Methods. High spectral resolution observations of the fundamental ortho water (o-H2O) transition (557 GHz) were carried out with the Heterodyne Instrument for the Far Infrared onboard Herschel toward two starless cores: Barnard 68 (hereafter B68), a Bok globule, and LDN 1544 (L1544), a prestellar core embedded in the Taurus molecular cloud complex. Detailed radiative transfer and chemical codes were used to analyze the data.\ud Results. The RMS in the brightness temperature measured for the B68 and L1544 spectra is 2.0 and 2.2 mK, respectively, in a velocity bin of 0.59 km s-1. The continuum level is 3.5 ± 0.2 mK in B68 and 11.4 ± 0.4 mK in L1544. No significant feature is detected in B68 and the 3σ upper limit is consistent with a column density of o-H2O N(o-H2O) < 2.5 × 1013 cm-2, or a fractional abundance x(o-H2O) < 1.3 × 10-9, more than an order of magnitude lower than the SWAS upper limit on this source. The L1544 spectrum shows an absorption feature at a 5σ level from which we obtain the first value of the o-H2O column density ever measured in dark clouds: N(o-H2O) = (8 ± 4) × 1012 cm-2. The corresponding fractional abundance is x(o-H2O) 5 × 10-9 at radii >7000 AU and 2 × 10-10 toward the center. The radiative transfer analysis shows that this is consistent with a x(o-H2O) profile peaking at 10-8, 0.1 pc away from the core center, where both freeze-out and photodissociation are negligible.\ud Conclusions. Herschel has provided the first measurement of water vapor in dark regions. Column densities of o-H2O are low, but prestellar cores such as L1544 (with their high central densities, strong continuum, and large envelopes) appear to be very promising tools to finally shed light on the solid/vapor balance of water in molecular clouds and oxygen chemistry in the earliest stages of star formation.
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- 2010
21. Hydrides in Young Stellar Objects: Radiation tracers in a protostar-disk-outflow system
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Benz, A. O., Bruderer, S., van Dishoeck, E. F., Staeuber, P., Wampfler, S. F., Melchior, M., Dedes, C., Wyrowski, F., Doty, S. D., van der Tak, F., Baechtold, W., Csillaghy, A., Megej, A., Monstein, C., Soldati, M., Bachiller, R., Baudry, A., Benedettini, M., Bergin, E., Bjerkeli, P., Blake, G.A., Bontemps, S., Braine, J., Caselli, P., Cernicharo, J., Codella, C., Daniel, F., di Giorgio, A. M., Dieleman, P., Dominik, C., Encrenaz, P., Fich, M., Fuente, A., Giannini, T., Goicoechea, J. R., de Graauw, Th., Helmich, F., Herczeg, G. J., Herpin, F., Hogerheijde, M. R., Jacq, T., Jellema, W., Johnstone, D., Jorgensen, J. K., Kristensen, L. E., Larsson, B., Lis, D., Liseau, R., Marseille, M., McCoey, C., Melnick, G., Neufeld, D., Nisini, B., Olberg, M., Ossenkopf, V., Parise, B., Pearson, J. C., Plume, R., Risacher, C., Santiago-Garcia, J., Saraceno, P., Schieder, R., Shipman, R., Stutzki, J., Tafalla, M., Tielens, A. G. G. M., van Kempen, T. A., Visser, R., Yildiz, U. A., 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), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Civilisations atlantiques & Archéosciences (C2A), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ministère de la Culture et de la Communication (MCC)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Université de Nantes - UFR Histoire, Histoire de l'Art et Archéologie (UFR HHAA), Université de Nantes (UN)-Université de Nantes (UN), SRON Netherlands Institute for Space Research (SRON), Université de Nantes - UFR Histoire, Histoire de l'Art et Archéologie (UFR HHAA), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Ministère de la Culture et de la Communication (MCC), Low Energy Astrophysics (API, FNWI), and Astronomy
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H3O+ ,Astronomy ,Young stellar object ,FOS: Physical sciences ,Context (language use) ,Astrophysics ,Radiation ,01 natural sciences ,7. Clean energy ,W3IRS5 ,photon-dominated region ,CHEMISTRY ,0103 physical sciences ,Protostar ,H2O+ ,010306 general physics ,010303 astronomy & astrophysics ,QB ,Line (formation) ,Physics ,stars: formation ,SPECTROSCOPY ,astrochemistry ,DR21 ,Star formation ,[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] ,Astronomy and Astrophysics ,REGIONS ,[PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] ,Astrophysics - Astrophysics of Galaxies ,stars: massive ,13. Climate action ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,submillimeter: ISM ,Outflow ,Absorption (chemistry) ,line: identification - Abstract
Context: Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays. Aims: We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation. Methods: W3 IRS5 was observed by HIFI on the Herschel Space Observatory with deep integration (about 2500 s) in 8 spectral regions. Results: The target lines including CH, NH, H3O+, and the new molecules SH+, H2O+, and OH+ are detected. The H2O+ and OH+ J=1-0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H2O+ and OH+ also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds. Conclusions: The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation., Comment: Astronomy and Astrophysics Letters, in press
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- 2010
22. Detection of interstellar oxidaniumyl: Abundant H2O+ towards the star-forming regions DR21, Sgr B2, and NGC6334
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Ossenkopf, V., Müller, H. S. P., Lis, D. C., Schilke, P., Bell, T. A., Bruderer, S., Bergin, E., Ceccarelli, C., Comito, C., Stutzki, J., Bacman, A., Baudry, Alain, Benz, A. O., Benedettini, M., Berne, O., Blake, G., Boogert, A., Bottinelli, S., Boulanger, F., Cabrit, S., Caselli, P., Caux, E., Cernicharo, J., Codella, C., Coutens, A., Crimier, N., Crockett, N. R., Daniel, F., Demyk, K., Dieleman, P., Dominik, C., Dubernet, M. L., Emprechtinger, M., Encrenaz, P., Falgarone, E., France, K., Fuente, A., Gerin, M., Giesen, T. F., Di Giorgio, A. M., Goicoechea, J. R., Goldsmith, P. F., Güsten, R., Harris, A., Helmich, F., Herbst, E., Hily-Blant, Pierre, Jacobs, K., Jacq, T., Joblin, Ch., Johnstone, D., Kahane, C., Kama, M., Klein, T., Klotz, A., Kramer, C., Langer, W., Lefloch, B., Leinz, C., Lorenzani, A., Lord, S. D., Maret, S., Martin, P. G., Martin-Pintado, J., McCoey, C., Melchior, M., Melnick, G. J., Menten, K. M., Mookerjea, B., Morris, P., Murphy, J. A., Neufeld, D. A., Nisini, B., Pacheco, S., Pagani, L., Parise, B., Pearson, J. C., Pérault, M., Phillips, T. G., Plume, R., Quin, S.-L., Rizzo, R., Röllig, M., Salez, M., Saraceno, P., Schlemmer, S., Simon, R., Schuster, K., Van Der Tak, F. F. S., Tielens, A. G. G. M., Teyssier, D., Trappe, N., Vastel, C., Viti, S., Wakelam, Valentine, Walters, A., Wang, S., Whyborn, N., Van Der Wiel, M., Yorke, H. W., Yu, S., Zmuidzinas, J., Laboratoire d'Astrophysique de Grenoble (LAOG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
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ComputingMilieux_MISCELLANEOUS - Abstract
International audience
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- 2010
23. Effect of Gemfibrozil on The Pharmacokinetics of Selexipag, An oral Prostacyclin Receptor Agonist, And Its Active Metabolite In Healthy Male Subjects
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Bruderer, S., Petersen-Sylla, M., Boehler, M., Remeňová, T., Halabi, A., and Dingemanse, J.
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- 2017
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24. Effect of Rifampicin on The Pharmacokinetics of Selexipag, An Oral Prostacyclin Receptor Agonist, and Its Active Metabolite In Healthy Male Subjects
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Bruderer, S., Petersen-Sylla, M., Boehler, M., Remeňová, T., Halabi, A., and Dingemanse, J.
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- 2017
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25. Biocomparison Study of Adult And Pediatric Dose Strengths of The Prostacyclin Receptor Agonist Selexipag
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Boehler, M., Bruderer, S., Ulč, I., and Dingemanse, J.
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- 2017
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26. Far-infrared HD emission as a measure of protoplanetary disk mass.
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Trapman, L., Miotello, A., Kama, M., van Dishoeck, E. F., and Bruderer, S.
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PROTOPLANETARY disks ,ORIGIN of planets ,CARBON monoxide ,ISOTOPOLOGUES ,ASTROCHEMISTRY - Abstract
Context. Protoplanetary disks around young stars are the sites of planet formation. While the dust mass can be estimated using standard methods, determining the gas mass - and thus the amount of material available to form giant planets - has proven to be very difficult. Hydrogen deuteride (HD) is a promising alternative to the commonly used gas mass tracer, carbon monoxide. However, the potential of HD has not yet been investigated with models incorporating both HD and CO isotopologue-specific chemistry, and its sensitivity to uncertainties in disk parameters has not yet been quantified. Aims. We examine the robustness of HD as tracer of the disk gas mass, specifically the effect of gas mass on HD far-infrared emission and its sensitivity to the vertical structure. Also, we seek to provide requirements for future far-infrared missions such as SPICA. Methods. Deuterium chemistry reactions relevant for HD were implemented in the thermochemical code DALI and more than 160 disk models were run for a range of disk masses and vertical structures. Results. The HD J = 1-0 line intensity depends directly on the gas mass through a sublinear power law relation with a slope of ~0.8. Assuming no prior knowledge about the vertical structure of a disk and using only the HD 1-0 flux, gas masses can be estimated to within a factor of two for low mass disks (M
disk ≤ 10-3 M☉). For more massive disks, this uncertainty increases to more than an order of magnitude. Adding the HD 2-1 line or independent information about the vertical structure can reduce this uncertainty to a factor of ~ 3 for all disk masses. For TW Hya, using the radial and vertical structure from the literature, the observations constrain the gas mass to 6 × 10-3 M☉ ≤ Mdisk ≤ 9 × 10-3 M☉. Future observations require a 5σ sensitivity of 1.8 × 10-20 W m-2 (2.5 × 10-20 W m-2 ) and a spectral resolving power R ≥ 300 (1000) to detect HD 1-0 (HD 2-1) for all disk masses above 10-5M☉ with a line-to-continuum ratio ≥ 0.01. Conclusions. These results show that HD can be used as an independent gas mass tracer with a relatively low uncertainty and should be considered an important science goal for future far-infrared missions. [ABSTRACT FROM AUTHOR]- Published
- 2017
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27. Different dust and gas radial extents in protoplanetary disks: consistent models of grain growth and CO emission.
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Facchini, S., Birnstiel, T., Bruderer, S., and van Dishoeck, E. F.
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PROTOPLANETARY disks ,ISOTOPOLOGUES ,ACCRETION disks ,ASTROCHEMISTRY ,PLANETARY systems - Abstract
Context. ALMA observations of protoplanetary disks confirm earlier indications that there is a clear difference between the dust and gas radial extents. The origin of this difference is still debated, with both radial drift of the dust and optical depth effects suggested in the literature. Aims. In thermo-chemical models, the dust properties are usually prescribed by simple parametrisations. In this work, the feedback of more realistic dust particle distributions onto the gas chemistry and molecular emissivity is investigated, with a particular focus on CO isotopologues. Methods. The radial dust grain size distribution is determined using dust evolution models that include growth, fragmentation, and radial drift for a given static gas density structure. The vertical settling of dust particles is computed in steady-state. A new version of the code DALI is used to take into account how dust surface area and density influence the disk thermal structure, molecular abundances, and excitation. Synthetic images of both continuum thermal emission and low J CO isotopologues lines are produced. Results. The difference of dust and gas radial sizes is largely due to differences in the optical depth of CO lines and millimeter continuum, without the need to invoke radial drift. The effect of radial drift is primarily visible in the sharp outer edge of the continuum intensity profile. The gas outer radius probed by
12 CO emission can easily differ by a factor of ~two between the models for a turbulent α ranging between 10-4 and 10-2 , with the ratio of the CO and mm radius Rout CO =Rout mm increasing with turbulence. Grain growth and settling concur in thermally decoupling the gas and dust components, due to the low collision rate with large grains. As a result, the gas can be much colder than the dust at intermediate heights, reducing the CO excitation and emission, especially for low turbulence values. Also, due to disk mid-plane shadowing, a second CO thermal desorption (rather than photodesorption) front can occur in the warmer outer mid-plane disk. The models are compared to ALMA observations of HD 163296 as a test case. In order to reproduce the observed CO snowline of the system, a binding energy for CO typical of ice mixtures, with Eb ≥ 1100 K, needs to be used rather than the lower pure CO value. Conclusions. The difference between observed gas and dust extent is largely due to optical depth effects, but radial drift and grain size evolution also affect the gas and dust emission in subtle ways. In order to properly infer fundamental quantities of the gaseous component of disks, such as disk outer radii and gas surface density profiles, simultaneous modelling of both dust and gas observations including dust evolution is needed. [ABSTRACT FROM AUTHOR]- Published
- 2017
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28. Population Modeling of Selexipag Pharmacokinetics and Clinical Response Parameters in Patients With Pulmonary Arterial Hypertension.
- Author
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Krause, A, Machacek, M, Lott, D, Hurst, N, Bruderer, S, and Dingemanse, J
- Subjects
PULMONARY hypertension treatment ,PHARMACOKINETICS ,ORAL drug administration ,PROSTACYCLIN ,DRUG metabolism ,THERAPEUTICS - Abstract
Selexipag (Uptravi) is an oral selective IP prostacyclin receptor agonist approved for the treatment of pulmonary arterial hypertension (PAH). The pivotal GRIPHON study was the largest clinical study ever conducted in PAH patients, providing long-term data from 1,156 patients. PAH comedication did not affect exposure to selexipag, while exposure to its active metabolite ACT-333679 was reduced by 30% when taken in combination, clinically not relevant in the context of individual dose up-titration. Using log-linear regression models linking model-predicted steady-state exposure to pharmacodynamics (PD), exposure to selexipag and ACT-333679 showed some statistically significant, albeit not clinically relevant, effects on exercise capacity, laboratory values, and the occurrence of prostacyclin-related adverse events, but not on vital signs or adverse events denoting hemorrhage. Using suitable modeling techniques, the GRIPHON study yielded clinically relevant data with limited burden of pharmacokinetics (PK) blood sampling, demonstrating that PK/PD modeling enables firm conclusions even with sparse PK and PD sampling. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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29. ALMA unveils rings and gaps in the protoplanetary system HD 169142: signatures of two giant protoplanets.
- Author
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Fedele, D., Carney, M., Hogerheijde, M. R., Walsh, C., Miotello, A., Klaassen, P., Bruderer, S., Henning, Th., and van Dishoeck, E. F.
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PROTOPLANETARY disks ,IMAGING systems in astronomy ,COSMIC dust ,NEAR infrared spectroscopy ,GAS dynamics - Abstract
The protoplanetary system HD 169142 is one of the few cases where a potential candidate protoplanet has recently been detected by direct imaging in the near-infrared. To study the interaction between the protoplanet and the disk itself, observations of the gas and dust surface density structure are needed. This paper reports new ALMA observations of the dust continuum at 1.3 mm,
12 CO,13 CO, and C18 O J = 2-1 emission from the system HD 169142 (which is observed almost face-on) at an angular resolution of ~ (~35 × 20 au). The dust continuum emission reveals a double-ring structure with an inner ring between (~20-35 au) and an outer ring between (~56-83 au). The size and position of the inner ring is in good agreement with previous polarimetric observations in the near-infrared and is consistent with dust trapping by a massive planet. No dust emission is detected inside the inner dust cavity (R ܐ 20 au) or within the dust gap (~35-56 au) down to the noise level. In contrast, the channel maps of the J = 2-1 line of the three CO isotopologs reveal gas inside the dust cavity and dust gap. The gaseous disk is also much larger than the compact dust emission; it extends to ~1 (~180 au) in radius. This difference and the sharp drop of the continuum emission at large radii point to radial drift of large dust grains (>µm size). Using the thermo-chemical disk code dali, we modeled the continuum and the CO isotopolog emission to quantitatively measure the gas and dust surface densities. The resulting gas surface density is reduced by a factor of ~30-40 inward of the dust gap. The gas and dust distribution indicate that two giant planets shape the disk structure through dynamical clearing (dust cavity and gap) and dust trapping (double-ring dust distribution). [ABSTRACT FROM AUTHOR]- Published
- 2017
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30. Quantifying the Gas Inside Dust Cavities in Transitional Disks: Implications for Young Planets.
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van Dishoeck, E. F., van der Marel, N., Bruderer, S., and Pinilla, P.
- Published
- 2015
31. A low-mass protostar's disk-envelope interface: disk-shadowing evidence from ALMA DCO+ observations of VLA1623.
- Author
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Murillo, N. M., Bruderer, S., van Dishoeck, E. F., Walsh, C., Harsono, D., Lai, S.-P., and Fuch, C. M.
- Subjects
- *
ISOTOPOLOGUES , *LOW mass stars , *INTERFEROMETRY , *PROTOSTARS , *SPECTRAL energy distribution , *STAR observations , *STAR formation - Abstract
Context. Historically, due to instrumental limitations and a lack of disk detections, the structure of the transition from the envelope to the rotationally supported disk has been poorly studied. This is now possible with ALMA through observations of CO isotopologues and tracers of freezeout. Class 0 sources are ideal for such studies given their almost intact envelope and young disk. Aims. The structure of the disk-envelope interface of the prototypical Class 0 source, VLA1623A, which has a confirmed Keplerian disk, is constrained through modeling and analysis of ALMA observations of DCO+ (3-2) and C18O (2-1) rotational lines. Methods. The physical structure of VLA1623 is obtained from the large-scale spectral energy distribution (SED) and continuum radiative transfer. An analytic model using a simple network coupled with radial density and temperature profiles is used as input for a 2D line radiative transfer calculation for comparison with the ALMA Cycle 0 12-m array and Cycle 2 ACA observations of VLA1623. Results. The DCO+ emission shows a clumpy structure bordering VLA1623A's Keplerian disk. This suggests a cold ring-like structure at the disk-envelope interface. The radial position of the observed DCO+ peak is reproduced in our model only if the region's temperature is between 11 K and 16 K, lower than expected from models constrained by continuum data and source SED. Altering the density profile has little e ect on the DCO+ peak position, but increased density is needed to reproduce the observed C18O tracing the disk. Conclusions. The observed DCO+ (3-2) emission around VLA1623A is the product of shadowing of the envelope by the disk observed in C18O. Disk-shadowing causes a drop in the gas temperature outside of the disk on >200 AU scales, encouraging the production of deuterated molecules. This indicates that the physical structure of the disk-envelope interface differs from the rest of the envelope, highlighting the drastic impact that the disk has on the envelope and temperature structure. The results presented here show that DCO+ is an excellent cold temperature tracer. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
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32. Gas density drops inside dust cavities of transitional disks around young stars observed with ALMA.
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van der Marel, N., van Dishoeck, E. F., Bruderer, S., Pérez, L., and Isella, A.
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INTERSTELLAR gases ,STAR formation ,INTERPLANETARY dust ,ASTROCHEMISTRY ,PROTOPLANETARY disks ,SPECTRAL energy distribution - Abstract
Context. Transitional disks with large dust cavities are important laboratories in which to study planet formation and disk evolution. Cold gas may still be present inside these cavities, but quantying this gas is challenging. The gas content is important for constraining the origin of the dust cavity. Aims. We use Atacama Large Millimeter/submillimeter Array (ALMA) observations of
12 CO 6-5 and 690 GHz (Band 9) continuum of five well-studied transitional disks. In addition, we analyze previously published Band 7 observations of a disk in the12 CO 3-2 line and 345 GHz continuum. The observations are used to set constraints on the gas and dust surface density profiles, in particular, the drop δgas of the gas density inside the dust cavity. Methods. The physical-chemical modeling code DALI was used to simultaneously analyze the gas and dust images. We modeled SR21, HD135344B, LkCa15, SR24S, and RXJ1615-3255 (Band 9) and J1604-2130 (Band 7). The spectral energy distribution and continuum visibility curve constrain the dust surface density. Then we used the same model to calculate the12 CO emission, which we compared with the observations through spectra and intensity cuts. The amount of gas inside the cavity was quantified by varying the δgas parameter. Results. Model fits to the dust and gas indicate that gas is still present inside the dust cavity for all disks, but at a reduced level. The gas surface density drops inside the cavity by at least a factor 10, while the dust density drops by at least a factor 1000. Disk masses are comparable with previous estimates from the literature, cavity radii are found to be smaller than in the data obtained with the 345 GHz SubMillimeter Array. Conclusions. The derived gas surface density profiles suggest that the cavity was cleared by one or more companions in all cases, which trapped the millimeter-sized dust at the edge of the cavity. [ABSTRACT FROM AUTHOR]- Published
- 2015
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33. Testing protostellar disk formation models with ALMA observations.
- Author
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Harsono, D., van Dishoeck, E. F., Bruderer, S., Li, Z.-Y., and Jørgensen, J. K.
- Subjects
STAR formation ,ACCRETION disks ,MAGNETOHYDRODYNAMICS ,RADIATIVE transfer - Abstract
Context. Recent simulations have explored different ways to form accretion disks around low-mass stars. However, it has been difficult to differentiate between the proposed mechanisms because of a lack of observable predictions from these numerical studies. Aims. We aim to present observables that can differentiate a rotationally supported disk from an infalling rotating envelope toward deeply embedded young stellar objects (M
env > Mdisk ) and infer their masses and sizes. Methods. Two 3D magnetohydrodynamics (MHD) formation simulations are studied with a rotationally supported disk (RSD) forming in one but not the other (where a pseudo-disk is formed instead), together with the 2D semi-analytical model. We determine the dust temperature structure through continuum radiative transfer RADMC3D modeling. A simple temperature-dependent CO abundance structure is adopted and synthetic spectrally resolved submm rotational molecular lines up to Ju = 10 are compared with existing data to provide predictions for future ALMA observations. Results. The 3D MHD simulations and 2D semi-analytical model predict similar compact components in continuum if observed at the spatial resolutions of 0.5-1'' (70-140 AU) typical of the observations to date. A spatial resolution of ~14 AU and high dynamic range (>1000) are required in order to differentiate between RSD and pseudo-disk formation scenarios in the continuum. The first moment maps of the molecular lines show a blue- to red-shifted velocity gradient along the major axis of the flattened structure in the case of RSD formation, as expected, whereas it is along the minor axis in the case of a pseudo-disk. The peak position-velocity diagrams indicate that the pseudo-disk shows a flatter velocity profile with radius than does an RSD. On larger scales, the CO isotopolog line profiles within large (>9'') beams are similar and are narrower than the observed line widths of low-J (2-1 and 3-2) lines, indicating significant turbulence in the large-scale envelopes. However a forming RSD can provide the observed line widths of high-J (6-5, 9-8, and 10-9) lines. Thus, either RSDs are common or a higher level of turbulence (b ~ 0:8 km s-1 ) is required in the inner envelope compared with the outer part (0.4 km s-1 ). Conclusions. Multiple spatially and spectrally resolved molecular line observations can differentiate between the pseudo-disk and the RSD much better than continuum data. The continuum data give a better estimate of disk masses, whereas the disk sizes can be estimated from the spatially resolved molecular lines observations. The general observable trends are similar between the 2D semi-analytical models and 3D MHD RSD simulations. [ABSTRACT FROM AUTHOR]- Published
- 2015
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34. Protoplanetary disk masses from CO isotopologue line emission.
- Author
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Miotello, A., Bruderer, S., and van Dishoeck, E. F.
- Subjects
- *
PROTOPLANETARY disks , *ASTROCHEMISTRY , *RADIATIVE transfer , *ISOTOPOLOGUES , *ASTRONOMICAL research - Abstract
Context. One of the methods for deriving disk masses relies on direct observations of the gas, whose bulk mass is in the outer cold regions (T ≲ 30 K). This zone can be well traced by rotational lines of less abundant CO isotopologues such as 13CO, C18O, and C17O, which probe the gas down to the midplane. The total CO gas mass is then obtained with the isotopologue ratios taken to be constant at the elemental isotope values found in the local interstellar medium. This approach is imprecise, however, because isotope-selective processes are ignored. Aims. The aim of this work is an isotopologue-selective treatment of CO isotopologues, to obtain a more accurate determination of disk masses. Methods. The isotope-selective photodissociation, the main process controlling the abundances of CO isotopologues in the CO-emissive layer, is properly treated for the first time in a full-disk model. The chemistry, thermal balance, line, and continuum radiative transfer are all considered together with a chemical network that treats 13CO, C18O and C17O, isotopes of all included atoms and molecules as independent species. Results. Isotope selective processes lead to regions in the disk where the isotopologue abundance ratios of C18O/12CO, for example, are considerably di erent from the elemental 18O/16O ratio. The results of this work show that considering CO isotopologue ratios as constants can lead to underestimating disk masses by up to an order of magnitude or more if grains have grown to larger sizes. This may explain observed discrepancies in mass determinations from di erent tracers. The dependence of the various isotopologue emission on stellar and disk parameters is investigated to set the framework for the analysis of ALMA data. Conclusions. Including CO isotope selective processes is crucial for determining the gas mass of the disk accurately (through ALMA observations) and thus for providing the amount of gas that may eventually form planets or change the dynamics of forming planetary systems. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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- View/download PDF
35. Warm formaldehyde in the Ophiuchus IRS 48 transitional disk.
- Author
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van der Marel, N., van Dishoeck, E. F., Bruderer, S., and van Kempen, T. A.
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FORMALDEHYDE ,PROTOPLANETARY disks ,CHEMICAL models ,PLANETESIMALS ,STAR formation - Abstract
Context. Simple molecules such as H
2 CO and CH3 OH in protoplanetary disks are the starting point for the production of more complex organic molecules. So far, the observed chemical complexity in disks has been limited because of freeze-out of molecules onto grains in the bulk of the cold outer disk. Aims. Complex molecules can be studied more directly in transitional disks with large inner holes because these have a higher potential of detection through the UV heating of the outer disk and the directly exposed midplane at the wall. Methods. We used Atacama Large Millimeter/submillimeter Array (ALMA) Band 9 (~680 GHz) line data of the transitional disk Oph IRS 48, which was previously shown to have a large dust trap, to search for complex molecules in regions where planetesimals are forming. Results. We report the detection of the H2 CO 9(1, 8)-8(1, 7) line at 674 GHz, which is spatially resolved as a semi-ring at ~60 AU radius centered south from the star. The inferred H2 CO abundance is ~10-8 , derived by combining a physical disk model of the source with a non-LTE excitation calculation. Upper limits for CH3 OH lines in the same disk give an abundance ratio H2 CO/CH3 OH >0.3, which indicates that both ice formation and gas-phase routes play a role in the H2 CO production. Upper limits on the abundances of H13 CO+, CN and several other molecules in the disk were also derived and found to be consistent with full chemical models. Conclusions. The detection of the H2 CO line demonstrates the start of complex organic molecules in a planet-forming disk. Future ALMA observations are expected to reduce the abundance detection limits of other molecules by 1-2 orders of magnitude and test chemical models of organic molecules in (transitional) disks. [ABSTRACT FROM AUTHOR]- Published
- 2014
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- View/download PDF
36. Rotationally-supported disks around Class I sources in Taurus: disk formation constraints.
- Author
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Harsono, D., Jørgensen, J. K., van Dishoeck, E. F., Hogerheijde, M. R., Bruderer, S., Persson, M. V., and Mottram, J. C.
- Subjects
TAURUS (Constellation) ,STELLAR rotation ,PROTOSTARS ,STELLAR mass ,PROTOPLANETARY disks ,ACCRETION (Astrophysics) - Abstract
Context. Disks are observed around pre-main sequence stars, but how and when they form is still heavily debated. While disks around young stellar objects have been identified through thermal dust emission, spatially and spectrally resolved molecular line observations are needed to determine their nature. Only a handful of embedded rotationally supported disks have been identified to date. Aims. We identify and characterize rotationally supported disks near the end of the main accretion phase of low-mass protostars by comparing their gas and dust structures. Methods. Subarcsecond observations of dust and gas toward four Class I low-mass young stellar objects in Taurus are presented at significantly higher sensitivity than previous studies. The
13 CO and C18 O J = 2-1 transitions at 220 GHz were observed with the Plateau de Bure Interferometer at a spatial resolution of ⩽0.8" (56 AU radius at 140 pc) and analyzed using uv-space position velocity diagrams to determine the nature of their observed velocity gradient. Results. Rotationally supported disks (RSDs) are detected around 3 of the 4 Class I sources studied. The derived masses identify them as Stage I objects; i.e., their stellar mass is higher than their envelope and disk masses. The outer radii of the Keplerian disks toward our sample of Class I sources are ⩽100 AU. The lack of on-source C18 O emission for TMR1 puts an upper limit of 50 AU on its size. Flattened structures at radii >100 AU around these sources are dominated by infalling motion (υ ∝ r-1 ). A large-scale envelope model is required to estimate the basic parameters of the flattened structure from spatially resolved continuum data. Similarities and differences between the gas and dust disk are discussed. Combined with literature data, the sizes of the RSDs around Class I objects are best described with evolutionary models with an initial rotation of Ω = 10-14 Hz and slow sound speeds. Based on the comparison of gas and dust disk masses, little CO is frozen out within 100 AU in these disks. Conclusions. Rotationally supported disks with radii up to 100 AU are present around Class I embedded objects. Larger surveys of both Class 0 and I objects are needed to determine whether most disks form late or early in the embedded phase. [ABSTRACT FROM AUTHOR]- Published
- 2014
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37. Far-infrared molecular lines from low- to high-mass star forming regions observed with Herschel.
- Author
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Karska, A., Herpin, F., Bruderer, S., Goicoechea, J. R., Herczeg, G. J., van Dishoeck, E. F., José-García, I. San, Contursi, A., Feuchtgruber, H., Fedele, D., Baudry, A., Braine, J., Chavarría, L., Cernicharo, J., van der Tak, F. F. S., and Wyrowski, F.
- Subjects
STAR formation ,STELLAR mass ,CARBON monoxide ,LUMINOSITY ,TEMPERATURE of stars ,INFRARED spectroscopy ,ASTROCHEMISTRY ,PROTOSTARS - Abstract
Aims. Our aim is to study the response of the gas-to-energetic processes associated with high-mass star formation and compare it with previously published studies on low- and intermediate-mass young stellar objects (YSOs) using the same methods. The quantified far-IR line emission and absorption of CO, H
2 O, OH, and [Oi] reveals the excitation and the relative contribution of different atomic and molecular species to the gas cooling budget. Methods. Herschel/PACS spectra covering 55-190 μm are analyzed for ten high-mass star forming regions of luminosities Lbol ~ 104 -106 L☉ and various evolutionary stages on spatial scales of ~104 AU. Radiative transfer models are used to determine the contribution of the quiescent envelope to the far-IR CO emission. Results. The close environments of high-mass protostars show strong far-IR emission from molecules, atoms, and ions. Water is detected in all 10 objects even up to high excitation lines, often in absorption at the shorter wavelengths and in emission at the longer wavelengths. CO transitions from J = 14-13 up to typically 29-28 (Eu/kB ~ 580-2400 K) show a single temperature component with a rotational temperature of Trot ~ 300 K. Typical H2 O excitation temperatures are Trot ~250 K, while OH has Trot ~ 80 K. Far-IR line cooling is dominated by CO (~75%) and, to a smaller extent, by [Oi] (~20%), which becomes more important for the most evolved sources. H2 O is less important as a coolant for high-mass sources because many lines are in absorption. Conclusions. Emission from the quiescent envelope is responsible for ~45-85% of the total CO luminosity in high-mass sources compared with only ~10% for low-mass YSOs. The highest-J lines (Jup ⩾ 20) originate most likely in shocks, based on the strong correlation of CO and H2 O with physical parameters (Lbol , Menv ) of the sources from low- to high-mass YSOs. The excitation of warm CO described by Trot ~ 300 K is very similar for all mass regimes, whereas H2 O temperatures are ~100 K high for high-mass sources compared with low-mass YSOs. The total far-IR cooling in lines correlates strongly with bolometric luminosity, consistent with previous studies restricted to low-mass YSOs.Molecular cooling (CO, H2 O, and OH) is ~4 times greater than cooling by oxygen atoms for all mass regimes. The total far-IR line luminosity is about 10-3 and 10-5 times lower than the dust luminosity for the low-and high-mass star forming regions, respectively. [ABSTRACT FROM AUTHOR]- Published
- 2014
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38. THE ATOMIC AND MOLECULAR CONTENT OF DISKS AROUND VERY LOW-MASS STARS AND BROWN DWARFS.
- Author
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Pascucci, I., Herczeg, G., Carr, J. S., and Bruderer, S.
- Subjects
STELLAR mass ,DWARF stars ,T Tauri stars ,BROWN dwarf stars ,PLANETS - Abstract
There is growing observational evidence that disk evolution is stellar-mass-dependent. Here, we show that these dependencies extend to the atomic and molecular content of disk atmospheres. We analyze a unique dataset of high-resolution Spitzer/IRS spectra from eight very low mass star and brown dwarf disks. We report the first detections of Ne
+ , H2 , CO2 , and tentative detections of H2 O toward these faint and low-mass disks. Two of our [Ne II] 12.81 μm emission lines likely trace the hot (⩾5000 K) disk surface irradiated by X-ray photons from the central stellar/sub-stellar object. The H2 S(2) and S(1) fluxes are consistent with arising below the fully or partially ionized surface traced by the [Ne II] emission in gas at ∼600 K. We confirm the higher C2 H2 /HCN flux and column density ratio in brown dwarf disks previously noted from low-resolution IRS spectra. Our high-resolution spectra also show that the HCN/H2 O fluxes of brown dwarf disks are on average higher than those of T Tauri disks. Our LTE modeling hints that this difference extends to column density ratios if H2 O lines trace warm ⩾600 K disk gas. These trends suggest that the inner regions of brown dwarf disks have a lower O/C ratio than those of T Tauri disks, which may result from a more efficient formation of non-migrating icy planetesimals. An O/C = 1, as inferred from our analysis, would have profound implications on the bulk composition of rocky planets that can form around very low mass stars and brown dwarfs. [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
- View/download PDF
39. DIGIT survey of far-infrared lines from protoplanetary disks I. [O I], [CII], OH, H2O, and CH+.
- Author
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Fedele, D., Bruderer, S., van Dishoeck, E. F., Carr, J., G. J. Herczeg, Salyk, C., Evans II, N. J., Bouwman, J., Meeus, G., Henning, Th., Green, J., Najita, J. R., and Güdel, M.
- Subjects
- *
STAR observations , *PROTOPLANETARY disks , *ASTRONOMICAL surveys , *SPECTRAL lines , *MOLECULAR astrophysics , *ASTROCHEMISTRY - Abstract
We present far-infrared (50-200 μm) spectroscopic observations of young pre-main-sequence stars taken with Herschel/PACS as part of the DIGIT key project. The sample includes 16 Herbig AeBe and 4 T Tauri sources observed in SED mode covering the entire spectral range. An additional 6 Herbig AeBe and 4 T Tauri systems have been observed in SED mode with a limited spectral coverage. Multiple atomic fine structure and molecular lines are detected at the source position: [O I], [C II], CO, OH, H2O, CH+. The most common feature is the [O I] 63 μm line detected in almost all of the sources, followed by OH. In contrast with CO, OH is detected toward both Herbig AeBe groups (flared and non-flared sources). An isothermal LTE slab model fit to the OH lines indicates column densities of 1013 < NOH < 1016 cm-2, emitting radii 15 < r < 100AU and excitation temperatures 100 < Tex < 400 K. We used the non-LTE code RADEX to verify the LTE assumption. High gas densities (n ⩾ 1010 cm-3) are needed to reproduce the observations. The OH emission thus comes from a warm layer in the disk at intermediate stellar distances. Warm H2O emission is detected through multiple lines toward the T Tauri systems AS 205, DG Tau, S CrA and RNO 90 and three Herbig AeBe systems HD 104237, HD 142527, HD 163296 (through line stacking). Overall, Herbig AeBe sources have higher OH/H2O abundance ratios across the disk than do T Tauri disks, from near- to far-infrared wavelengths. Far-infrared CH+ emission is detected toward HD 100546 and HD 97048. The slab model suggests moderate excitation (Tex ~ 100K) and compact (r ~ 60AU) emission in the case of HD 100546. Off-source [O I] emission is detected toward DG Tau, whose origin is likely the outflow associated with this source. The [CII] emission is spatially extended in all sources where the line is detected. This suggests that not all [CII] emission is associated with the disk and that there is a substantial contribution from diffuse material around the young stars. The flux ratios of the atomic fine structure lines ([O I] 63 μm, [O I] 145 μm, [CII]) are analyzed with PDR models and require high gas density (n ⩾ 105 cm-3) and high UV fluxes (Go ~ 103-107), consistent with a disk origin for the oxygen lines for most of the sources. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
40. DIGIT survey of far-infrared lines from protoplanetary disks I. [O I], [CII], OH, H2O, and CH+.
- Author
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Fedele, D., Bruderer, S., van Dishoeck, E. F., Carr, J., G. J. Herczeg, Salyk, C., Evans II, N. J., Bouwman, J., Meeus, G., Henning, Th., Green, J., Najita, J. R., and Güdel, M.
- Subjects
STAR observations ,PROTOPLANETARY disks ,ASTRONOMICAL surveys ,SPECTRAL lines ,MOLECULAR astrophysics ,ASTROCHEMISTRY - Abstract
We present far-infrared (50-200 μm) spectroscopic observations of young pre-main-sequence stars taken with Herschel/PACS as part of the DIGIT key project. The sample includes 16 Herbig AeBe and 4 T Tauri sources observed in SED mode covering the entire spectral range. An additional 6 Herbig AeBe and 4 T Tauri systems have been observed in SED mode with a limited spectral coverage. Multiple atomic fine structure and molecular lines are detected at the source position: [O I], [C II], CO, OH, H
2 O, CH+ . The most common feature is the [O I] 63 μm line detected in almost all of the sources, followed by OH. In contrast with CO, OH is detected toward both Herbig AeBe groups (flared and non-flared sources). An isothermal LTE slab model fit to the OH lines indicates column densities of 1013 < NOH < 1016 cm-2 , emitting radii 15 < r < 100AU and excitation temperatures 100 < Tex < 400 K. We used the non-LTE code RADEX to verify the LTE assumption. High gas densities (n ⩾ 1010 cm-3 ) are needed to reproduce the observations. The OH emission thus comes from a warm layer in the disk at intermediate stellar distances. Warm H2 O emission is detected through multiple lines toward the T Tauri systems AS 205, DG Tau, S CrA and RNO 90 and three Herbig AeBe systems HD 104237, HD 142527, HD 163296 (through line stacking). Overall, Herbig AeBe sources have higher OH/H2 O abundance ratios across the disk than do T Tauri disks, from near- to far-infrared wavelengths. Far-infrared CH+ emission is detected toward HD 100546 and HD 97048. The slab model suggests moderate excitation (Tex ~ 100K) and compact (r ~ 60AU) emission in the case of HD 100546. Off-source [O I] emission is detected toward DG Tau, whose origin is likely the outflow associated with this source. The [CII] emission is spatially extended in all sources where the line is detected. This suggests that not all [CII] emission is associated with the disk and that there is a substantial contribution from diffuse material around the young stars. The flux ratios of the atomic fine structure lines ([O I] 63 μm, [O I] 145 μm, [CII]) are analyzed with PDR models and require high gas density (n ⩾ 105 cm-3 ) and high UV fluxes (Go ~ 103 -107 ), consistent with a disk origin for the oxygen lines for most of the sources. [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
- View/download PDF
41. Infall motions towards Class 0/I envelopes as probed by water.
- Author
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Mottram, J. C., Van Dishoeck, E. F., Schmalzl, M., Kristensen, L. E., Visser, R., Hogerheijde, M. R., and Bruderer, S.
- Subjects
STAR formation ,PROTOSTARS ,RADIAL velocity of stars ,KINEMATICS ,RADIATIVE transfer ,COSMIC abundances - Abstract
Context. For stars to form, material must fall inwards from core scales through the envelope towards the central protostar. While theories of how this takes place have been around for some time, the velocity profile around protostars is poorly constrained. The combination of observations in multiple transitions of a tracer which is sensitive to kinematics and radiative transfer modelling of those lines has the potential to break this deadlock. Aims. Seven protostars observed with the Heterodyne Instrument for the Far-Infrared (HIFI) on board the Herschel Space Observatory as part of the "Water in star-forming regions with Herschel" (WISH) survey show infall signatures in water line observations. We aim to constrain the infall velocity and the radii over which infall is taking place within the protostellar envelopes of these sources. We will also use these data to constrain the chemistry of cold water. Methods. We use 1-D non-LTE ratran radiative transfer models of the observed water lines to constrain the infall velocity and chemistry in the protostellar envelopes of six Class 0 protostars and one Class I source. We assume a free-fall velocity profile and, having found the best fit, vary the radii over which infall takes place. Results. In the well-studied Class 0 protostar NGC1333-IRAS4A we find that our observations probe infall over the whole envelope to which our observations are sensitive (r ≳ 1000 AU). For L1527, L1157, BHR71 and IRAS 15398 infall takes place on core to envelope scales (i.e. ~10 000-3000 AU). In Serpens-SMM4 and GSS30 the inverse P-Cygni profiles seen in the ground-state lines are more likely due to larger-scale motions or foreground clouds. Models including a simple consideration of the chemistry are consistent with the observations, while using step abundance profiles are not. The non-detection of excited water in the inner envelope in six out of seven protostars is further evidence that water must be heavily depleted from the gas-phase at these radii. Conclusions. Infall in four of the sources is supersonic and in all sources must take place at the outer edge of the envelope, which may be evidence that collapse is global or outside-in rather than inside-out. The mass infall rate in NGC1333-IRAS4A is large (≳10-4 M☉ yr
-1 ), higher than the mass outflow rate and expected mass accretion rates onto the star. This suggests that any flattened disk-like structure on small scales will be gravitationally unstable, potentially leading to rotational fragmentation and/or episodic accretion. [ABSTRACT FROM AUTHOR]- Published
- 2013
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42. PP192—Pharmacokinetics of Selexipag in Subjects with Severe Renal Impairment Compared with Healthy Subjects
- Author
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Fischer, N., Cruz, H., Bruderer, S., Petersen-Sylla, M., Halabi, A., and Dingemanse, J.
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- 2013
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43. PP194—Pharmacokinetics of Selexipag in Subjects with Mild, Moderate, or Severe Hepatic Impairment Compared with Healthy Subjects
- Author
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Fischer, N., Kaufmann, P., Bruderer, S., Ulč, I., and Dingemanse, J.
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- 2013
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44. Observational evidence for dissociative shocks in the inner 100 AU of low-mass protostars using Herschel-HIFI.
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Kristensen, L. E., van Dishoeck, E. F., Benz, A.O., Bruderer, S., Visser, R., and Wampfler, S. F.
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DISSOCIATION (Chemistry) ,PROTOSTARS ,STAR formation ,HYDRIDES ,ULTRAVIOLET radiation - Abstract
Aims. Herschel-HIFI spectra of H
2 O towards low-mass protostars show a distinct velocity component not seen in observations from the ground of CO or other species. The aim is to characterise this component in terms of excitation conditions and physical origin. Methods. A velocity component with an offset of ~10 km s-1 detected in spectra of the H2 O 110 -101 557 GHz transition towards six low-mass protostars in the "Water in star-forming regions with Herschel" (WISH) programme is also seen in higher-excited H2 O lines. The emission from this component is quantified and local excitation conditions are inferred using 1D slab models. Data are compared to observations of hydrides (high-J CO, OH+ , CH+ , C+ , OH) where the same component is uniquely detected. Results. The velocity component is detected in all six targeted H2 O transitions (Eup ~ 50-250 K), as well as in CO 16-15 towards one source, Ser SMM1. Inferred excitation conditions imply that the emission arises in dense (n ~ 5 × 106 -108 cm-3 ) and hot (T ~ 750 K) gas. The H2 O and CO column densities are ≳1016 and 1018 cm-2 , respectively, implying a low H2 O abundance of ~10-2 with respect to CO. The high column densities of ions such as OH+ and CH+ (both ≳1013 cm-2 ) indicate an origin close to the protostar where the UV field is strong enough that these species are abundant. The estimated radius of the emitting region is 100 AU. This component likely arises in dissociative shocks close to the protostar, an interpretation corroborated by a comparison with models of such shocks. Furthermore, one of the sources, IRAS 4A, shows temporal variability in the offset component over a period of two years which is expected from shocks in dense media. High-J CO gas detected with Herschel-PACS with Trot ~ 700 K is identified as arising in the same component and traces the part of the shock where H2 reforms. Thus, H2 O reveals new dynamical components, even on small spatial scales in low-mass protostars. [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
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45. Water in star-forming regions with Herschel (WISH).
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Karska, A., Herczeg, G. J., van Dishoeck, E. F., Wampfler, S. F., Kristensen, L. E., Goicoechea, J. R., Visser, R., Nisini, B., San José-García, I., Bruderer, S., Sniady, P., Doty, S., Fedele, D., Yildiz, U. A., Benz, A. O., Bergin, E., Caselli, P., Herpin, F., Hogerheijde, M. R., and Johnstone, D.
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STAR formation ,ENERGY dissipation ,GAS air conditioning ,PROTOSTARS ,STELLAR luminosity function ,PHOTODISSOCIATION - Abstract
Context. Understanding the physical phenomena involved in the earlierst stages of protostellar evolution requires knowledge of the heating and cooling processes that occur in the surroundings of a young stellar object. Spatially resolved information from its constituent gas and dust provides the necessary constraints to distinguish between different theories of accretion energy dissipation into the envelope. Aims. Our aims are to quantify the far-infrared line emission from low-mass protostars and the contribution of different atomic and molecular species to the gas cooling budget, to determine the spatial extent of the emission, and to investigate the underlying excitation conditions. Analysis of the line cooling will help us characterize the evolution of the relevant physical processes as the protostar ages. Methods. Far-infrared Herschel-PACS spectra of 18 low-mass protostars of various luminosities and evolutionary stages are studied in the context of the WISH key program. For most targets, the spectra include many wavelength intervals selected to cover specific CO, H2O, OH, and atomic lines. For four targets the spectra span the entire 55-200 µm region. The PACS field-of-view covers ~47" with the resolution of 9.4". Results. Most of the protostars in our sample show strong atomic and molecular far-infrared emission. Water is detected in 17 out of 18 objects (except TMC1A), including 5 Class I sources. The high-excitation H
2 O 818 -707 63.3 µm line (Eu /kB = 1071 K) is detected in 7 sources. CO transitions from J = 14-13 up to J = 49 - 48 are found and show two distinct temperature components on Boltzmann diagrams with rotational temperatures of ~350 K and ~700 K. H2 O has typical excitation temperatures of ~150 K. Emission from both Class 0 and I sources is usually spatially extended along the outflow direction but with a pattern that depends on the species and the transition. In the extended sources, emission is stronger off source and extended on =10?000 AU scales; in the compact sample, more than half of the flux originates within 1000 AU of the protostar. The H2O line fluxes correlate strongly with those of the high-J CO lines, both for the full array and for the central position, as well as with the bolometric luminosity and envelope mass. They correlate less strongly with OH fluxes and not with [OI] fluxes. In contrast, [OI] and OH often peak together at the central position. Conclusions. The PACS data probe at least two physical components. The H2 O and CO emission very likely arises in non-dissociative (irradiated) shocks along the outflow walls with a range of pre-shock densities. Some OH is also associated with this component, most likely resulting from H2 O photodissociation. UV-heated gas contributes only a minor fraction to the CO emission observed by PACS, based on the strong correlation between the shock-dominated CO 24-23 line and the CO 14-13 line. [OI] and some of the OH emission probe dissociative shocks in the inner envelope. The total far-infrared cooling is dominated by H2 O and CO, with the fraction contributed by [OI] increasing for Class I sources. Consistent with previous studies, the ratio of total far-infrared line emission over bolometric luminosity decreases with the evolutionary state. [ABSTRACT FROM AUTHOR]- Published
- 2013
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46. OH far-infrared emission from low- and intermediate-mass protostars surveyed with Herschel-PACS.
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Wampfler, S. F., Bruderer, S., Karska, A., Herczeg, G. J., van Dishoeck, E. F., Kristensen, L. E., Goicoechea, J. R., Benz, A. O., Doty, S. D., McCoey, C., Baudry, A., Giannini, T., and Larsson, B.
- Subjects
- *
WATER chemistry , *STREAM chemistry , *PROTOSTARS , *ASTRONOMY , *ASTROPHYSICS - Abstract
Context. The OH radical is a key species in the water chemistry network of star-forming regions, because its presence is tightly related to the formation and destruction of water. Previous studies of the OH far-infrared emission from low- and intermediate-mass protostars suggest that the OH emission mainly originates from shocked gas and not from the quiescent protostellar envelopes. Aims. We aim to study the excitation of OH in embedded low- and intermediate-mass protostars, determine the influence of source parameters on the strength of the emission, investigate the spatial extent of the OH emission, and further constrain its origin. Methods. This paper presents OH observations from 23 low- and intermediate-mass young stellar objects obtained with the PACS integral field spectrometer on-board Herschel in the context of the "Water In Star-forming regions with Herschel" (WISH) key program. Radiative transfer codes are used to model the OH excitation. Results. Most low-mass sources have compact OH emission (≲5000 AU scale), whereas the OH lines in most intermediate-mass sources are extended over the whole 47."0 × 47."0 PACS detector field-of-view (≳20 000 AU). The strength of the OH emission is correlated with various source properties such as the bolometric luminosity and the envelope mass, but also with the [OI] and H2O emission. Rotational diagrams for sources with many OH lines show that the level populations of OH can be approximated by a Boltzmann distribution with an excitation temperature at around 70 K. Radiative transfer models of spherically symmetric envelopes cannot reproduce the OH emission fluxes nor their broad line widths, strongly suggesting an outflow origin. Slab excitation models indicate that the observed excitation temperature can either be reached if the OH molecules are exposed to a strong far-infrared continuum radiation field or if the gas temperature and density are sufficiently high. Using realistic source parameters and radiation fields, it is shown for the case of Ser SMM1 that radiative pumping plays an important role in transitions arising from upper level energies higher than 300 K. The compact emission in the low-mass sources and the required presence of a strong radiation field and/or a high density to excite the OH molecules points toward an origin in shocks in the inner envelope close to the protostar. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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47. Excited OH+, H2O+, and H3O+ in NGC 4418 and Arp 220.
- Author
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González-Alfonso, E., Fischer, J., Bruderer, S., P.Müller, H. S., Graciá-Carpio, J., Sturm, E., Lutz, D., Poglitsch, A., Feuchtgruber, H., Veilleux, S., Contursi, A., Sternberg, A., Hailey-Dunsheath, S., Verma, A., Christopher, N., Davies, R., Genzel, R., and Tacconi, L.
- Subjects
PROPERTIES of matter ,ASTROPHYSICAL radiation ,COSMIC rays ,ASTRONOMY ,RADIATION - Abstract
We report on Herschel/PACS observations of absorption lines of OH
+ , H2 O+ and H3 O+ in NGC 4418 and Arp 220. Excited lines of OH+ and H2 O+ with Elower of at least 285 and ~200 K, respectively, are detected in both sources, indicating radiative pumping and location in the high radiation density environment of the nuclear regions. Abundance ratios OH+ /H2 O+ of 1-2.5 are estimated in the nuclei of both sources. The inferred OH+ column and abundance relative to H nuclei are (0.5-1) × 1016 cm-2 and ~2 × 10-8, respectively. Additionally, in Arp 220, an extended low excitation component around the nuclear region is found to have OH+ /H2 O+ ~ 5-10. H3 O+ is detected in both sources with N(H3 O+ ) ~ (0.5-2) × 1016 cm-2, and in Arp 220 the pure inversion, metastable lines indicate a high rotational temperature of ~500 K, indicative of formation pumping and/or hot gas. Simple chemical models favor an ionization sequence dominated by H+ → O+ → OH+ → H2 O+ → H3 O+ , and we also argue that the H+ production is most likely dominated by X-ray/cosmic ray ionization. The full set of observations and models leads us to propose that the molecular ions arise in a relatively low density (≳104 cm-3) interclump medium, in which case the ionization rate per H nucleus (including secondary ionizations) is ς > 10-13 s-1 , a lower limit that is several × 102 times the highest current rate estimates for Galactic regions. In Arp 220, our lower limit for ς is compatible with estimates for the cosmic ray energy density inferred previously from the supernova rate and synchrotron radio emission, and also with the expected ionization rate produced by X-rays. In NGC 4418, we argue that X-ray ionization due to an active galactic nucleus is responsible for the molecular ion production. [ABSTRACT FROM AUTHOR]- Published
- 2013
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- View/download PDF
48. Warm H2O and OH in the disk around the Herbig star HD 163296.
- Author
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Fedele, D., Bruderer, S., van Dishoeck, E. F., Herczeg, G. J., N.J. Evans II, Bouwman, J., Henning, Th., and Green, J.
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INFRARED absorption , *EMISSION control , *HERBIG Ae/Be stars , *PHOTODISSOCIATION , *ASTRONOMICAL observations , *THERMODYNAMIC equilibrium , *PROTOPLANETARY disks , *ASTROCHEMISTRY - Abstract
We present observations of far-infrared (50-200μm) OH and H2O emission of the disk around the Herbig Ae star HD 163296 obtained with Herschel/PACS in the context of the DIGIT key program. In addition to strong [OI] emission, a number of OH doublets and a few weak highly excited lines of H2O are detected. The presence of warm H2O in this Herbig disk is confirmed by a line stacking analysis, enabled by the full PACS spectral scan, and by lines seen in Spitzer data. The line fluxes are analyzed using a local-thermal-equilibrium slab model including line opacity. The H2O column density is 1014-1015cm-2, and the excitation temperature is 200-300 K, implying warm gas with a density n > 105?cm-3. For OH, we find Nmol of 1014-1015cm-2 and Tex ∼ 300-500 K. For both species, we find an emitting region of r ∼ 15-20AU from the star. We argue that the molecular emission arises from the protoplanetary disk rather than the outflow. This far-infrared detection of both H2O and OH contrasts with near- and mid-infrared observations, which have generally found a lack of water in the inner disk around Herbig AeBe stars owing to the strong photodissociation of H2O. Given the similar column density and emitting region, OH and H2O emission seems to arise from an upper layer of the disk atmosphere of HD 163296, which probes a new reservoir of water. The slightly lower temperature of H2O compared to OH suggests a vertical stratification of the molecular gas with OH located higher and H2O deeper in the disk, consistent with thermo-chemical models. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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- View/download PDF
49. Water in star-forming regions with Herschel (WISH) II. Evolution of 557 GHz 110-101 emission in low-mass protostars.
- Author
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Kristensen, L. E., van Dishoeck, E. F., Bergin, E. A., Visser, R., Yildiz, U. A., San Jose-Garcia, I., Jørgensen, J. K., Herczeg, G. J., Johnstone, D., Wampfler, S. F., Benz, A. O., Bruderer, S., Cabrit, S., Caselli, P., Doty, S. D., Harsono, D., Herpin, F., Hogerheijde, M. R., Karska, A., and van Kempen, T. A.
- Subjects
ASTRONOMICAL observations ,STAR formation ,SPECTRAL energy distribution ,PROTOSTARS ,BIPOLAR outflows (Astrophysics) - Abstract
Context. Water is a key tracer of dynamics and chemistry in low-mass star-forming regions, but spectrally resolved observations have so far been limited in sensitivity and angular resolution, and only data from the brightest low-mass protostars have been published. Aims. The first systematic survey of spectrally resolved water emission in 29 low-mass (L <40 Lʘ) protostellar objects is presented. The sources cover a range of luminosities and evolutionary states. The aim is to characterise the line profiles to distinguish physical components in the beam and examine how water emission changes with protostellar evolution. Methods. H
2 O was observed in the ground-slate 110 -101 transition at 557 GHz (Eup /kB -∼ 60K) as single-point observations with the Heterodyne Instrument for the Far-Infrared (HIFI) on Herschel in 29 deeply embedded Class 0 and I low-mass protostars. Complementary far-R and tub-mm continuum data (including PACS data from our programme) are used to constrain the spectral energy distribution (SED) of each source. H20 intensities are compared to inferred envelope properties, e.g., mass and density, outflow properties and CO 3-2 emission. Results. H2 O emission is detected in all objects except one (TMCIA). The line profiles are complex and consist of several kinematic components tracing different physical regions in each system. In particular, the profiles are typically dominated by a broad Gaussian emission feature, indicating that the bulk of the water emission arises in outflows, not in the quiescent envelope. Several sources show multiple shock components appearing in either emission or absorption, thus constraining the internal geometry of the system. Furthermore, the components include inverse P-Cygni profiles in seven sources (nix Class 0, one Class 1) indicative of infalling envelopes, and regular P-Cygni profiles in four sources (three Class 1, one Class 0) indicative of expanding envelopes. Molecular "bullets" moving at ≳50 km s-1 with respect to the source are detected in four Class 0 sources; three of these sources were not known to harbour bullets previously. In the outflow, the H2 O/CO abundance ratio an a function of velocity in nearly the name for all line wings, increasing from 10-3 at low velocities (<5 km s-1 ) to ≳ 10-1 at high velocities (>10 km s-1 ). The water abundance in the outer cold envelope in low, ≳10-10 . The different H2 O profile components show a clear evolutionary trend: in the younger Class 0 sources the emission in dominated by outflow components originating inside an infalling envelope. When large-scale infall diminishes during the Class I phase, the outflow weakens and H2 O emission all but disappears. [ABSTRACT FROM AUTHOR]- Published
- 2012
- Full Text
- View/download PDF
50. The warm gas atmosphere of the HD 100546 disk seen by Herschel.
- Author
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Bruderer, S., Van Dishoeck, E. F., Doty, S. D., and Herczeg, G. J.
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PROTOPLANETARY disks , *ACCRETION (Astrophysics) , *CARBON monoxide , *RADIATIVE transfer , *CARBON , *ASTROPHYSICS - Abstract
Context. With the Herschel Space Observatory, lines of simple molecules (C+, O, and high-J lines of CO, Jup ≳ 14) have been observed in the atmosphere of protoplanetary disks. When combined with ground-based data on [C i], all principle forms of carbon can be studied. These data allow us to test model predictions for the main carbon-bearing species and verify the presence of a warm surface layer. The absence of neutral carbon [Ci], which is predicted by models to be strong, can then be interpreted together with ionized carbon [C ii] and carbon monoxide. Aims. We study the gas temperature, excitation, and chemical abundance of the simple carbon-bearing species C, C+, and CO, as well as O by the method of chemical-physical modeling. Using the models, we explore the sensitivity of the lines to the entering parameters and constrain the region from which the line radiation emerges. Methods. Numerical models of the radiative transfer in the lines and dust are used together with a chemical network simulation and a calculation of the gas energetics to obtain the gas temperature. We present our new model, which is based on our previous models but includes several improvements that we report in detail, together with the results of benchmark tests. Results. A model of the disk around the Herbig Be star HD 100546 is able to reproduce the CO ladder together with the atomic finestructure lines of [O i] and either [C i] or [Cii].We find that the high-J lines of CO can only be reproduced by a warm atmosphere with Tgas ⪢ Tdust. The low-J lines of CO, observable from the ground, are dominated by the outer disk with a radius of several 100 AU, while the high-J CO observable with Herschel-PACS are dominated from regions within some tens of AU. The spectral profiles of high-J lines of CO are predicted to be broader than those of the low-J lines. We study the effect of several parameters including the size of the disk, the gas mass of the disk, the PAH abundance and distribution, and the amount of carbon in the gas phase. Conclusions. The main conclusions of our work are (i) only a warm atmosphere with Tgas ⪢ Tdust can reproduce the CO ladder. (ii) The CO ladder together with [O i] and the upper limit to [Ci] can be reproduced by models with a high gas/dust ratio and a low abundance of volatile carbon. These models however produce too small amounts of [Cii]. Models with a low gas/dust ratio and more volatile carbon also reproduce CO and [O i], are in closer agreement with observations of [Cii], but overproduce [C i]. Owing to the uncertain origin of the [Cii] emission, we prefer the high gas/dust ratio models, indicating a low abundance of volatile carbon. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
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