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1. Sub-kiloparsec empirical relations and excitation conditions of HCN and HCO+ J = 3–2 in nearby star-forming galaxies

Author

A. García-Rodríguez, A. Usero, A. K. Leroy, F. Bigiel, M. J. Jiménez-Donaire, D. Liu, M. Querejeta, T. Saito, E. Schinnerer, A. Barnes, F. Belfiore, I. Bešlić, Y. Cao, M. Chevance, D. A. Dale, J. S. den Brok, C. Eibensteiner, S. García-Burillo, S. C. O. Glover, R. S. Klessen, J. Pety, J. Puschnig, E. Rosolowsky, K. Sandstrom, M. C. Sormani, Y.-H. Teng, and T. G. Williams

Subjects
Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

We present new HCN and HCO$^+$ ($J$=3-2) images of the nearby star-forming galaxies (SFGs) NGC 3351, NGC 3627, and NGC 4321. The observations, obtained with the Morita ALMA Compact Array, have a spatial resolution of $\sim$290-440 pc and resolve the inner $R_\textrm{gal} \lesssim$ 0.6-1 kpc of the targets, as well as the southern bar end of NGC 3627. We complement this data set with publicly available images of lower excitation lines of HCN, HCO$^+$, and CO and analyse the behaviour of a representative set of line ratios: HCN(3-2)/HCN(1-0), HCN(3-2)/HCO$^+$(3-2), HCN(1-0)/CO(2-1), and HCN(3-2)/CO(2-1). Most of these ratios peak at the galaxy centres and decrease outwards. We compare the HCN and HCO$^+$ observations with a grid of one-phase, non-local thermodynamic equilibrium (non-LTE) radiative transfer models and find them compatible with models that predict subthermally excited and optically thick lines. We study the systematic variations of the line ratios across the targets as a function of the stellar surface density ($\Sigma_\textrm{star}$), the intensity-weighted CO(2-1) ($\langle I_\text{CO}\rangle$), and the star formation rate surface density ($\Sigma_\text{SFR}$). We find no apparent correlation with $\Sigma_\text{SFR}$, but positive correlations with the other two parameters, which are stronger in the case of $\langle I_\text{CO}\rangle$. The HCN/CO-$\langle I_\text{CO}\rangle$ relations show $\lesssim$0.3 dex galaxy-to-galaxy offsets, with HCN(3-2)/CO(2-1)-$\langle I_\text{CO}\rangle$ being $\sim$2 times steeper than HCN(1-0)/CO(2-1). In contrast, the HCN(3-2)/HCN(1-0)-$\langle I_\text{CO}\rangle$ relation exhibits a tighter alignment between galaxies. We conclude that the overall behaviour of the line ratios cannot be ascribed to variations in a single excitation parameter (e.g. density or temperature)., Comment: Accepted for publication in A&A. 14 pages, 8 figures

Published
2023
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2. Erratum: 'Mapping Metallicity Variations across Nearby Galaxy Disks' (2019, ApJ, 887, 80)

Author

Andreas Schruba, K. Kreckel, Takashi Saito, Patricia Sanchez-Blazquez, E. Emsellem, I-Ting Ho, F. Santoro, Frank Bigiel, M. Chevance, Brent Groves, Sharon E. Meidt, J. Pety, Karin Sandstrom, Erik Rosolowsky, G. Blanc, K. Grasha, Eva Schinnerer, Christopher M Faesi, Enrico Congiu, S. C. O. Glover, R. McElroy, Philipp Lang, J. M. D. Kruijssen, Adam K. Leroy, 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, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY)

Subjects
Physics, [PHYS]Physics [physics], Space and Planetary Science, Metallicity, Astronomy and Astrophysics, Astrophysics, Table (information), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Galaxy, ComputingMilieux_MISCELLANEOUS
Abstract

We have noticed an error in the radial metallicity gradient fits provided in Table 3 (Appendix C) of the published article. The columns that list the metallicity gradients have units of dex arcmin-1, rather than the noted dex kpc-1. In the following we provide a corrected version of the table. All figures in the published article are shown in units of R25, and are unchanged from the published version. The results and conclusions of the paper are not affected by this error.

Published
2021
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3. The Organization of Cloud-scale Gas Density Structure: High-resolution CO versus 3.6 μm Brightness Contrasts in Nearby Galaxies

Author

Frank Bigiel, Brent Groves, Toshiki Saito, M. Querejeta, Annie Hughes, Christopher M Faesi, S. C. O. Glover, Ashley T. Barnes, Yixian Cao, M. Chevance, Daizhong Liu, Jonathan D. Henshaw, Eva Schinnerer, C. N. Herrera, Eric Emsellem, Guillermo A. Blanc, Andreas Schruba, J. M. Diederik Kruijssen, Thomas G. Williams, Elizabeth Watkins, K. Grasha, Jiayi Sun, R. S. Klessen, Erik Rosolowsky, Arjen Van der Wel, Hsi-An Pan, J. Pety, K. Kreckel, A. Usero, Daniel A. Dale, Adam K. Leroy, Sharon Meidt, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institut de RadioAstronomie Millimétrique (IRAM), and Centre National de la Recherche Scientifique (CNRS)

Subjects
PROBABILITY-DISTRIBUTION FUNCTIONS, Brightness, Galaxy structure, Scale (ratio), High resolution, Cloud computing, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, STAR-FORMATION EFFICIENCY, 01 natural sciences, Interstellar medium, TO-LIGHT-RATIO, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Disk galaxies, Astrophysics::Galaxy Astrophysics, Physics, Molecular gas, Spiral galaxy, Spiral galaxies, 010308 nuclear & particles physics, business.industry, SPITZER SURVEY, S(4)G IRAC 3.6, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, SELF-GRAVITATION, Galaxy, Physics and Astronomy, Space and Planetary Science, [SDU]Sciences of the Universe [physics], MOLECULAR CLOUDS, STELLAR MASS DISTRIBUTIONS, VELOCITY DISPERSION, business, SPIRAL GALAXIES
Abstract

In this paper we examine the factors that shape the distribution of molecular gas surface densities on the 150 pc scale across 67 morphologically diverse star-forming galaxies in the PHANGS-ALMA CO (2-1) survey. Dividing each galaxy into radial bins, we measure molecular gas surface density contrasts, defined here as the ratio between a fixed high percentile of the CO distribution and a fixed reference level in each bin. This reference level captures the level of the faint CO floor that extends between bright filamentary features, while the intensity level of the higher percentile probes the structures visually associated with bright, dense ISM features like spiral arms, bars, and filaments. We compare these contrasts to matched percentile-based measurements of the 3.6 $\mu$m emission measured using Spitzer/IRAC imaging, which trace the underlying stellar mass density. We find that the logarithms of CO contrasts on 150 pc scales are 3-4 times larger than, and positively correlated with, the logarithms of 3.6 $\mu$m contrasts probing smooth non-axisymmetric stellar bar and spiral structures. The correlation appears steeper than linear, consistent with the compression of gas as it flows supersonically in response to large-scale stellar structures, even in the presence of weak or flocculent spiral arms. Stellar dynamical features appear to play an important role in setting the cloud-scale gas density in our galaxies, with gas self-gravity perhaps playing a weaker role in setting the 150 pc-scale distribution of gas densities., Comment: Accepted for publication in ApJ, 16 pages, 7 figures

Published
2021
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4. Effect of microchannels on the crashworthiness of fiber-reinforced composites

Author

Philip R. Barnett, Stephen J. Pety, Anthony C. Gendusa, Scott R. White, Nancy R. Sottos, Quinn A. Calvert, and Jia En Aw

Subjects
Work (thermodynamics), Chamfer, Materials science, business.industry, 02 engineering and technology, Structural engineering, Fiber-reinforced composite, Edge (geometry), 021001 nanoscience & nanotechnology, 020303 mechanical engineering & transports, 0203 mechanical engineering, Crack initiation, Ceramics and Composites, Channel spacing, Specific energy, Crashworthiness, Composite material, 0210 nano-technology, business, Civil and Structural Engineering
Abstract

The integration of microchannels within structural composites enables a range of multifunctional responses such as thermal management and self-healing. In this work, we investigate how microchannels affect the crashworthiness of the host material. Corrugated panels are fabricated with aligned microchannels (ca. 400 µm diameter) at different channel spacing (10 mm and 1.2 mm), orientation with respect to the loading direction, and alignment with respect to the surrounding fiber-reinforcement. Specific energy absorbed (SEA) is measured by compression testing of samples with a chamfer edge trigger. SEA was preserved within 10% for all test cases. Flat (non-corrugated) panels are also tested to demonstrate that microchannels can serendipitously trigger stable, energy absorbing failure modes that lead to improved crashworthiness. Non-vascular panels without an edge chamfer fail catastrophically when compressed. In dramatic contrast, vascular panels fail in a stable fashion triggered by crack initiation at the microchannels, yielding ca. 10 times more energy absorption.

Published
2018
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5. Carbon fiber composites with 2D microvascular networks for battery cooling

Author

Scott R. White, Ahmad R. Najafi, Marcus Hwai Yik Tan, Philip R. Barnett, Philippe H. Geubelle, and Stephen J. Pety

Subjects
Fluid Flow and Transfer Processes, Battery (electricity), business.product_category, Materials science, 020209 energy, Mechanical Engineering, Composite number, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Volumetric flow rate, Heat flux, Electric vehicle, Thermal, 0202 electrical engineering, electronic engineering, information engineering, Vacuum assisted resin transfer molding, Composite material, 0210 nano-technology, business, Communication channel
Abstract

Electric vehicle (EV) batteries require both thermal regulation and crash protection. A novel battery packaging scheme is presented that uses microvascular composite panels with 2D channel networks to accomplish both objectives. Microvascular carbon fiber/epoxy composite panels are fabricated by vacuum assisted resin transfer molding, with the channel network formed by post-cure vaporization of an embedded polylactide channel template. Panel cooling performance is evaluated for parallel, bifurcating, serpentine, and spiral channel designs at different coolant flow rates and channel diameter. The spiral design provides the best thermal performance, but requires high pumping pressure (>100 kPa) at the flow rates needed for adequate cooling (>30 mL min −1 ). The bifurcating design and a network obtained by computational optimization offer much lower pressure with slightly reduced thermal performance. Channel diameter has negligible effect on cooling performance, but strongly affects pumping pressure. Computational fluid dynamics (CFD) simulations are also performed and correlate well with the experimental data. Simulations confirm that microvascular composite panels can cool typical battery cells generating 500 W m −2 heat flux below the target temperature of 40 °C.

Published
2017
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6. High-velocity hot CO emission close to Sgr A*

Author

J R, Goicoechea, M G, Santa-Maria, D, Teyssier, J, Cernicharo, M, Gerin, and J, Pety

Subjects
Article
Abstract

The properties of molecular gas, the fuel that forms stars, inside the cavity of the circumnuclear disk (CND) are not well constrained. We present results of a velocity-resolved submillimeter scan (~480 to 1250 GHz) and [C ii] 158 μm line observations carried out with Herschel/HIFI toward Sgr A*; these results are complemented by a ~2′×2′ (12)CO (J=3-2) map taken with the IRAM 30 m telescope at ~7″ resolution. We report the presence of high positive-velocity emission (up to about +300 km s(−1)) detected in the wings of (12)CO J=5-4 to 10-9 lines. This wing component is also seen in H(2)O (1(1,0)-1(0,1)), a tracer of hot molecular gas; in [C ii]158 μm, an unambiguous tracer of UV radiation; but not in [C i] 492, 806 GHz. This first measurement of the high-velocity (12)CO rotational ladder toward Sgr A* adds more evidence that hot molecular gas exists inside the cavity of the CND, relatively close to the supermassive black hole (< 1 pc). Observed by ALMA, this velocity range appears as a collection of (12)CO (J=3-2) cloudlets lying in a very harsh environment that is pervaded by intense UV radiation fields, shocks, and affected by strong gravitational shears. We constrain the physical conditions of the high positive-velocity CO gas component by comparing with non-LTE excitation and radiative transfer models. We infer T(k)≃400 K to 2000 K for n(H)≃(0.2-1.0)·10(5) cm(−3). These results point toward the important role of stellar UV radiation, but we show that radiative heating alone cannot explain the excitation of this ~10-60 M(⊙) component of hot molecular gas inside the central cavity. Instead, strongly irradiated shocks are promising candidates.

Published
2019

7. Dense gas is not enough: environmental variations in the star formation efficiency of dense molecular gas at 100 pc scales in M 51

Author

J. Pety, Eric J. Murphy, Andreas Schruba, Christopher M Faesi, S. C. O. Glover, Dyas Utomo, Sharon E. Meidt, Santiago García-Burillo, Eva Schinnerer, M. Chevance, Adam K. Leroy, Emmanuel Momjian, J. M. D. Kruijssen, Frank Bigiel, Alexander P. S. Hygate, M. Gallagher, A. Usero, Miguel Querejeta, M. J. Jimenez-Donaire, Erik Rosolowsky, 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, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)

Subjects
Stellar mass, Infrared, Continuum (design consultancy), MODELS, FOS: Physical sciences, DUST, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, SYNTHESIS, HII-REGIONS, 01 natural sciences, Luminosity, individual: NGC 5194 [galaxies], MAGELLANIC CLOUDS, 0103 physical sciences, NEARBY GALAXIES, FORMATION LAW, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], Spiral galaxy, ISM [galaxies], 010308 nuclear & particles physics, Star formation, Velocity dispersion, NGC-5194 M51A, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, FORMATION RATES, HCN, Stars, Physics and Astronomy, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), structure [galaxies], star formation [galaxies], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], UNCERTAINTY PRINCIPLE
Abstract

It remains unclear what sets the efficiency with which molecular gas transforms into stars. Here we present a new VLA map of the spiral galaxy M51 in 33GHz radio continuum, an extinction-free tracer of star formation, at 3" scales (~100pc). We combined this map with interferometric PdBI/NOEMA observations of CO(1-0) and HCN(1-0) at matched resolution for three regions in M51 (central molecular ring, northern and southern spiral arm segments). While our measurements roughly fall on the well-known correlation between total infrared and HCN luminosity, bridging the gap between Galactic and extragalactic observations, we find systematic offsets from that relation for different dynamical environments probed in M51, e.g. the southern arm segment is more quiescent due to low star formation efficiency (SFE) of the dense gas, despite having a high dense gas fraction. Combining our results with measurements from the literature at 100pc scales, we find that the SFE of the dense gas and the dense gas fraction anti-correlate and correlate, respectively, with the local stellar mass surface density. This is consistent with previous kpc-scale studies. In addition, we find a significant anti-correlation between the SFE and velocity dispersion of the dense gas. Finally, we confirm that a correlation also holds between star formation rate surface density and the dense gas fraction, but it is not stronger than the correlation with dense gas surface density. Our results are hard to reconcile with models relying on a universal gas density threshold for star formation and suggest that turbulence and galactic dynamics play a major role in setting how efficiently dense gas converts into stars., 23 pages, 9 figures, accepted for publication in A&A

Published
2019
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8. Gradient-based design of actively-cooled microvascular composite panels

Author

Stephen J. Pety, Scott R. White, Marcus Hwai Yik Tan, Ahmad R. Najafi, and Philippe H. Geubelle

Subjects
Fluid Flow and Transfer Processes, Optimal design, Microchannel, Computer science, Mechanical Engineering, Mechanical engineering, 02 engineering and technology, Solver, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Finite element method, 010101 applied mathematics, Temperature gradient, Mesh generation, Fluent, Shape optimization, 0101 mathematics, 0210 nano-technology
Abstract

Recent advances in manufacturing based on sacrificial fiber or template techniques have allowed complex networks of microchannels to be embedded in microvascular composites. In the thermal application of interest, a novel battery packaging scheme for electric vehicles is considered where each battery is surrounded by microvascular composite panels for temperature regulation and structural protection. We use simplified thermal and hydraulics models validated against more complex 3D FLUENT simulations and experiments to obtain the surface temperature distribution of the panel and the pressure drops across the microchannels. We further eliminate the cost and complexity associated with mesh generation by applying the interface-enriched generalized finite element method (IGFEM), which allows a non-conforming mesh to capture the discontinuous temperature gradient across the microchannels. The IGFEM thermal solver is then combined with a gradient-based shape optimization scheme to obtain optimal designs of a set of branched microchannel networks. The design parameters are the channel control points, which define the shape of the network. We use the p-mean as a differentiable objective function in place of the maximum temperature. To obtain accurate gradients with respect to the design parameters efficiently, we perform a sensitivity analysis based on a recently developed adjoint method for IGFEM. Starting from many distinct configurations, we obtain the optimal designs for a wide range of network topologies. We also investigate the effect of the coolant flow rate on the optimal design.

Published
2016
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9. 13 CO/C 18 O Gradients across the Disks of Nearby Spiral Galaxies

Author

K. F. Schuster, C. Kramer, J. Pety, Eric J. Murphy, D. Cormier, N. Tomicic, Adam K. Leroy, Eva Schinnerer, Mark R. Krumholz, Annie Hughes, M. J. Jimenez-Donaire, K. Sliwa, M. Gallagher, Frank Bigiel, David S. Meier, Andreas Schruba, A. Usero, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Department of Astronomy and Astrophysics [UCSC Santa Cruz], University of California [Santa Cruz] (UC Santa Cruz), University of California (UC)-University of California (UC), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, KOSMA, I. Physikalisches Institut, Universität zu Köln = University of Cologne, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Division of Geological and Planetary Sciences [Pasadena], California Institute of Technology (CALTECH), Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), University of California [Santa Cruz] (UCSC), University of California-University of California, Universität zu Köln, École normale supérieure - Paris (ENS Paris), California Institute of Technology (CALTECH)-NASA, 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, and PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP)

Subjects
Physics, Luminous infrared galaxy, [PHYS]Physics [physics], Spiral galaxy, 010308 nuclear & particles physics, Star formation, Milky Way, FOS: Physical sciences, Astronomy and Astrophysics, Natural abundance, Astrophysics, Radius, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Galaxy, Stellar nucleosynthesis, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS
Abstract

We use the IRAM Large Program EMPIRE and new high-resolution ALMA data to measure 13CO(1-0)/C18O(1-0) intensity ratios across nine nearby spiral galaxies. These isotopologues of CO are typically optically thin across most of the area in galaxy disks, and this ratio allows us to gauge their relative abundance due to chemistry or stellar nucleosynthesis effects. Resolved 13CO/C18O gradients across normal galaxies have been rare due to the faintness of these lines. We find a mean 13CO/C18O ratio of 6.0$\pm$0.9 for the central regions of our galaxies. This agrees well with results in the Milky Way, but differs from results for starburst galaxies (3.4$\pm$0.9) and ultraluminous infrared galaxies (1.1$\pm$0.4). In our sample, the 13CO/C18O ratio consistently increases with increasing galactocentric radius and decreases with increasing star formation rate surface density. These trends qualitatively agree with expectations for carbon and oxygen isotopic abundance variations due to stellar nucleosynthesis, with a possible effect of fractionation.

Published
2017
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10. Optical depth estimates and effective critical densities of dense gas tracers in the inner parts of nearby galaxy discs

Author

A. Usero, Molly J. Gallagher, Alberto D. Bolatto, Andreas Schruba, Mark R. Krumholz, Dario Colombo, David S. Meier, M. J. Jimenez-Donaire, Annie Hughes, Laura K. Zschaechner, J. Pety, Diane Cormier, Neven Tomičić, C. Kramer, Erik Rosolowsky, Frank Bigiel, Eric J. Murphy, Santiago García-Burillo, Eva Schinnerer, Adam K. Leroy, Zentrum für Astronomie der Universität Heidelberg (ZAH), Universität Heidelberg [Heidelberg], Observatorio Astronómico Nacional (OAN), oan, Department of Astronomy [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Observatorio Astronomico Nacional [Madrid] (OAN), Instituto Geografico Nacional (IGN), Instituto de RadioAstronomía Milimétrica (IRAM), Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), University of British Columbia (UBC), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Universität Heidelberg [Heidelberg] = Heidelberg University, Observatorio Astronomico Nacional, Madrid, and École normale supérieure - Paris (ENS-PSL)

Subjects
Physics, [PHYS]Physics [physics], Effective density, 010504 meteorology & atmospheric sciences, FOS: Physical sciences, High density, Astronomy and Astrophysics, Astrophysics, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Galaxy, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Optical depth (astrophysics), Isotopologue, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Line (formation)
Abstract

High critical density molecular lines like HCN(1-0) or HCO+(1-0) represent our best tool to study currently star-forming, dense molecular gas at extragalactic distances. The optical depth of these lines is a key ingredient to estimate the effective density required to excite emission. However, constraints on this quantity are even scarcer in the literature than measurements of the high density tracers themselves. Here, we combine new observations of HCN, HCO+ and HNC(1-0) and their optically thin isotopologues H13CN, H13CO+ and HN13C(1-0) to measure isotopologue line ratios. We use IRAM 30-m observations from the large program EMPIRE and new ALMA observations, which together target 6 nearby star-forming galaxies. Using spectral stacking techniques, we calculate or place strong upper limits on the HCN/H13CN, HCO+/H13CO+ and HNC/HN13C line ratios in the inner parts of these galaxies. Under simple assumptions, we use these to estimate the optical depths of HCN(1-0) and HCO+(1-0) to be \tau ~2-11 in the active, inner regions of our targets. The critical densities are consequently lowered to values between 5-20$\times 10^5$, 1-3$\times 10^5$ and 9$\times 10^4$ cm-3 for HCN, HCO+ and HNC, respectively. We study the impact of having different beam-filling factors, $\eta$, on these estimates and find that the effective critical densities decrease by a factor of $\frac{\eta_{12}}{\eta_{13}}\,\tau_{12}$. A comparison to existing work in NGC 5194 and NGC 253 shows HCN/H13CN and HCO+/H13CO+ ratios in agreement with our measurements within the uncertainties. The same is true for studies in other environments such as the Galactic Centre or nuclear regions of AGN-dominated nearby galaxies., Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society

Published
2017
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11. The ALMA view of UV irradiated cloud edges: unexpected structures and processes

Author

S. Cuadrado, Javier R. Goicoechea, C. Joblin, Octavio Roncero, Alfredo Aguado, Asunción Fuente, John H. Black, E. Chapillon, J. Pety, Emeric Bron, Maryvonne Gerin, José Cernicharo, Belén Tercero, Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Spanish National Research Council [Madrid] (CSIC), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), AMOR 2018, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatorio Astronomico Nacional, Madrid, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), 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), and 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)

Subjects
Physics, Astrochemistry, Photon, [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Molecular cloud, Ab initio, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Photodissociation region, 01 natural sciences, 7. Clean energy, Molecular physics, Astrophysics - Astrophysics of Galaxies, Ion, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Cluster (physics), Molecule, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Far-UV photons (E, Contributed paper to appear in: "Astrochemistry VII, Through the Cosmos from Galaxies to Planets". Proceedings of the IAU Symposium No. 332, 2017, Puerto Varas, Chile. M. Cunningham, T. Millar and Y. Aikawa, eds. (8 pages)

Published
2017
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12. AGN feedback in the nucleus of M51

Author

Kathryn Kreckel, Dario Colombo, Guillermo A. Blanc, J. Pety, Santiago García-Burillo, Eva Schinnerer, Miguel Querejeta, K. Sliwa, Sharon E. Meidt, Annie Hughes, Frank Bigiel, David S. Meier, and Adam K. Leroy

Subjects
ACTIVE GALACTIC NUCLEI, Active galactic nucleus, Radio galaxy, MASS-METALLICITY RELATION, DRIVEN MOLECULAR OUTFLOW, Astrophysics::High Energy Astrophysical Phenomena, jets [galaxies], FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, STAR-FORMATION, DISK, Seyfert [galaxies], 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Spiral galaxy, ISM [galaxies], 010308 nuclear & particles physics, Star formation, Plateau de Bure Interferometer, Astronomy and Astrophysics, QUASAR FEEDBACK, COLD GAS, Astrophysics - Astrophysics of Galaxies, Galaxy, Redshift, NGC 6240, GALAXIES, Interstellar medium, Physics and Astronomy, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), active [galaxies], BLACK-HOLE ACCRETION, structure [galaxies], STELLAR MASS
Abstract

AGN feedback is invoked as one of the most relevant mechanisms that shape the evolution of galaxies. Our goal is to understand the interplay between AGN feedback and the interstellar medium in M51, a nearby spiral galaxy with a modest AGN and a kpc-scale radio jet expanding through the disc of the galaxy. For that purpose, we combine molecular gas observations in the CO(1-0) and HCN(1-0) lines from the Plateau de Bure interferometer with archival radio, X-ray, and optical data. We show that there is a significant scarcity of CO emission in the ionisation cone, while molecular gas emission tends to accumulate towards the edges of the cone. The distribution and kinematics of CO and HCN line emission reveal AGN feedback effects out to r~500pc, covering the whole extent of the radio jet, with complex kinematics in the molecular gas which displays strong local variations. We propose that this is the result of the almost coplanar jet pushing on molecular gas in different directions as it expands; the effects are more pronounced in HCN than in CO emission, probably as the result of radiative shocks. Following previous interpretation of the redshifted molecular line in the central 5" as caused by a molecular outflow, we estimate the outflow rates to be Mdot_H2~0.9Msun/yr and Mdot_dense~0.6Msun/yr, which are comparable to the molecular inflow rates (~1Msun/yr); gas inflow and AGN feedback could be mutually regulated processes. The agreement with findings in other nearby radio galaxies suggests that this is not an isolated case, and probably the paradigm of AGN feedback through radio jets, at least for galaxies hosting low-luminosity active nuclei., 21 pages, 17 figures, accepted for publication in A&A

Published
2016

13. The first CO+ image: I. Probing the HI/H2 layer around the ultracompact HII region Mon R2

Author

J. R. Rizzo, Álvaro Sánchez-Monge, E. Roueff, P. Pilleri, Javier R. Goicoechea, C. Kramer, Olivier Berné, Volker Ossenkopf-Okada, J. Pety, A. Fuente, Marta Gónzalez-García, Santiago García-Burillo, Maryvonne Gerin, José Cernicharo, S. P. Treviño-Morales, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia e Innovación (España), European Research Council, German Research Foundation, and Centre National D'Etudes Spatiales (France)

Subjects
Astrochemistry, 010504 meteorology & atmospheric sciences, Gas velocity, Hii regions, Analytical chemistry, FOS: Physical sciences, Astrophysics, Spatial distribution, 01 natural sciences, Article, Ion, Laser linewidth, 0103 physical sciences, 010303 astronomy & astrophysics, Radio lines: ISM, 0105 earth and related environmental sciences, Line (formation), Physics, Range (particle radiation), Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, ISM [Radio lines], 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Photon-dominated region, Layer (electronics)
Abstract

The CO+ reactive ion is thought to be a tracer of the boundary between a HII region and the hot molecular gas. In this study, we present the spatial distribution of the CO+ rotational emission toward the Mon R2 star-forming region. The CO+ emission presents a clumpy ring-like morphology, arising from a narrow dense layer around the HII region. We compare the CO+ distribution with other species present in photon-dominated regions (PDR), such as [CII] 158 mm, H2 S(3) rotational line at 9.3 mm, polycyclic aromatic hydrocarbons (PAHs) and HCO+. We find that the CO+ emission is spatially coincident with the PAHs and [CII] emission. This confirms that the CO+ emission arises from a narrow dense layer of the HI/H2 interface. We have determined the CO+ fractional abundance, relative to C+ toward three positions. The abundances range from 0.1 to 1.9x10^(-10) and are in good agreement with previous chemical model, which predicts that the production of CO+ in PDRs only occurs in dense regions with high UV fields. The CO+ linewidth is larger than those found in molecular gas tracers, and their central velocity are blue-shifted with respect to the molecular gas velocity. We interpret this as a hint that the CO+ is probing photo-evaporating clump surfaces., Comment: The main text has 4 pages, 2 pages of Appendix, 4 figures, 1 table. Accepted for publication in Astronomy and Astrophysics letters

Published
2016

14. An Updated View of Giant Molecular Clouds, Gas Flows and Star Formation in M51 with PAWS

Author

Adam K. Leroy, G. Dumas, K. F. Schuster, Santiago García-Burillo, Eva Schinnerer, Annie Hughes, J. Pety, C. Kramer, Sharon E. Meidt, D. Colombo, Clare Dobbs, and T. A. Thompson

Subjects
Physics, Spiral galaxy, Space and Planetary Science, Star formation, Turbulence, Gas depletion, Molecular cloud, Astronomy, Astronomy and Astrophysics, Astrophysics, Surface pressure, External pressure
Abstract

We present an overview of the latest results from the PdBI Arcsecond Whirlpool Survey (PAWS, PI: E. Schinnerer), which has mapped CO(1-0) emission in the nearby grand-design spiral galaxy M51 at 40pc resolution. Our data are sensitive to GMCs above 105 M⊙, allowing the construction of the largest GMC catalog to date – containing over 1500 objects – using the CPROPS algorithm (Rosolowsky & Leroy 2006). In the inner disk of M51, the properties of the CO emission show significant variation that can be linked to the dynamical environment in which the molecular gas is located. We find that dynamically distinct regions host clouds with different properties and exhibit different GMC mass spectra, as well as distinct patterns of star formation. To understand how this sensitivity to environment emerges, we consider the role of pressure on GMC stabilization (including shear and star formation feedback-driven turbulence). We suggest that, in the presence of significant external pressure, streaming motions driven by the spiral arm can act to reduce the surface pressure on clouds. The resulting stabilization impacts the global pattern of star formation and can account for the observed non-monotonic radial dependence of the gas depletion time. Our findings have implications for the observed scatter in the standard GMC relations and extragalactic star formation laws.

Published
2012
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15. VELOCITY-RESOLVED [C ii] EMISSION AND [C ii]/FIR MAPPING ALONG ORION WITH

Author

Javier R, Goicoechea, D, Teyssier, M, Etxaluze, P F, Goldsmith, V, Ossenkopf, M, Gerin, E A, Bergin, J H, Black, J, Cernicharo, S, Cuadrado, P, Encrenaz, E, Falgarone, A, Fuente, A, Hacar, D C, Lis, N, Marcelino, G J, Melnick, H S P, Müller, C, Persson, J, Pety, M, Röllig, P, Schilke, R, Simon, R L, Snell, and J, Stutzki

Subjects
Article
Abstract

We present the first ~7.5′×11.5′ velocity-resolved (~0.2 km s−1) map of the [C ii] 158 μm line toward the Orion molecular cloud 1 (OMC 1) taken with the Herschel/HIFI instrument. In combination with far-infrared (FIR) photometric images and velocity-resolved maps of the H41α hydrogen recombination and CO J=2-1 lines, this data set provides an unprecedented view of the intricate small-scale kinematics of the ionized/PDR/molecular gas interfaces and of the radiative feedback from massive stars. The main contribution to the [C ii] luminosity (~85 %) is from the extended, FUV-illuminated face of the cloud (G0>500, nH>5×103 cm−3) and from dense PDRs (G≳104, nH≳105 cm−3) at the interface between OMC 1 and the H ii region surrounding the Trapezium cluster. Around ~15 % of the [C ii] emission arises from a different gas component without CO counterpart. The [C ii] excitation, PDR gas turbulence, line opacity (from [13C ii]) and role of the geometry of the illuminating stars with respect to the cloud are investigated. We construct maps of the L[C ii]/LFIR and LFIR/MGas ratios and show that L[C ii]/LFIR decreases from the extended cloud component (~10−2–10−3) to the more opaque star-forming cores (~10−3–10−4). The lowest values are reminiscent of the “[C ii] deficit” seen in local ultra-luminous IR galaxies hosting vigorous star formation. Spatial correlation analysis shows that the decreasing L[C ii]/LFIR ratio correlates better with the column density of dust through the molecular cloud than with LFIR/MGas. We conclude that the [C ii] emitting column relative to the total dust column along each line of sight is responsible for the observed L[C ii]/LFIR variations through the cloud.

Published
2015

16. Gravitational torques imply molecular gas inflow towards the nucleus of M51

Author

C. Kramer, J. Pety, K. F. Schuster, Adam K. Leroy, Annie Hughes, G. Dumas, D. Colombo, Clare Dobbs, Santiago García-Burillo, Eva Schinnerer, Miguel Querejeta, Sharon E. Meidt, Todd A. Thompson, Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Observatorio Astronomico Nacional, Madrid, Service d'ORL et de chirurgie cervicale, CHU Grenoble, Instituto de RadioAstronomía Milimétrica (IRAM), Centre National de la Recherche Scientifique (CNRS), Institut de RadioAstronomie Millimétrique (IRAM), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Observatorio Astronomico Nacional [Madrid] (OAN), Instituto Geografico Nacional (IGN), and École normale supérieure - Paris (ENS Paris)

Subjects
GALACTIC NUCLEI, individual: M 51 [galaxies], Astrophysics::High Energy Astrophysical Phenomena, nuclei [galaxies], FOS: Physical sciences, DWARF SEYFERT, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galactic nuclei, 01 natural sciences, SPIRAL SHOCKS, STAR-FORMATION, Marie curie, SUPERMASSIVE BLACK-HOLES, Seyfert [galaxies], kinematics and dynamics [galaxies], 0103 physical sciences, media_common.cataloged_instance, European union, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, media_common, Physics, [PHYS]Physics [physics], NUCLEI, ISM [galaxies], GALAXIES NUGA, IMAGES. II, 010308 nuclear & particles physics, SPITZER SURVEY, S(4)G IRAC 3.6, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Physics and Astronomy, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), structure [galaxies], STELLAR MASS DISTRIBUTIONS, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Humanities
Abstract

The transport of gas towards the centre of galaxies is critical for black hole feeding and, indirectly, it can control active galactic nucleus (AGN) feedback. We have quantified the molecular gas inflow in the central R, 19 pages, 12 figures. Accepted by A&A

Published
2015
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17. AGN feedback in the nucleus of M 51(Corrigendum)

Author

David S. Meier, Dario Colombo, Frank Bigiel, Sharon E. Meidt, Miguel Querejeta, Annie Hughes, Kathryn Kreckel, Adam K. Leroy, Guillermo A. Blanc, Santiago García-Burillo, Eva Schinnerer, J. Pety, K. Sliwa, Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Observatorio Astronomico Nacional [Madrid] (OAN), Instituto Geografico Nacional (IGN), Zentrum für Astronomie der Universität Heidelberg (ZAH), Universität Heidelberg [Heidelberg], 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), Observatorio Astronomico Nacional, Madrid, Universität Heidelberg [Heidelberg] = Heidelberg University, and École normale supérieure - Paris (ENS-PSL)

Subjects
[PHYS]Physics [physics], Luminous infrared galaxy, Physics, 010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, Quasar, Astrophysics, 01 natural sciences, medicine.anatomical_structure, Space and Planetary Science, 0103 physical sciences, medicine, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Nucleus, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

International audience

Published
2017
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19. Deuteration around the ultracompact HII region Monoceros R2

Author

C. Kramer, José Cernicharo, D. Ginard, M. González-García, O. Berne, Volker Ossenkopf, E. Roueff, J. Pety, Asunción Fuente, P. Pilleri, J. R. Rizzo, Santiago García-Burillo, S. Viti, M. Gerin, S. P. Treviño-Morales, J. R. Goicoechea, Los Alamos National Laboratory (LANL), Observatorio Astronómico Nacional (OAN), oan, Instituto de RadioAstronomía Milimétrica (IRAM), Centre National de la Recherche Scientifique (CNRS), 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), Instituto de Radio Astronomía Milimétrica, Spanish National Research Council [Madrid] (CSIC), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Institut de RadioAstronomie Millimétrique (IRAM), Centre 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, Observatorio Astronomico Nacional [Madrid] (OAN), Instituto Geografico Nacional (IGN), Atmospheric Physics Laboratory [UCL London], University College of London [London] (UCL), Observatorio Astronomico Nacional, Madrid, 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), École normale supérieure - Paris (ENS-PSL), 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), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS Paris)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Université Paris-Seine-Université Paris-Seine-Sorbonne Université (SU)-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), and Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, radio lines: ISM, astrochemistry, Spatially resolved, Hii regions, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics - Astrophysics of Galaxies, Deuterium, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), photon-dominated region (PDR), Protostar, Molecule, Spectral resolution, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract

The massive star-forming region Mon R2 hosts the closest ultra-compact HII region that can be spatially resolved with current single-dish telescopes. We used the IRAM-30m telescope to carry out an unbiased spectral survey toward two important positions (namely IF and MP2), in order to studying the chemistry of deuterated molecules toward Mon R2. We found a rich chemistry of deuterated species at both positions, with detections of C2D, DCN, DNC, DCO+, D2CO, HDCO, NH2D, and N2D+ and their corresponding hydrogenated species and isotopologs. Our high spectral resolution observations allowed us to resolve three velocity components: the component at 10 km/s is detected at both positions and seems associated with the layer most exposed to the UV radiation from IRS 1; the component at 12 km/s is found toward the IF position and seems related to the molecular gas; finally, a component at 8.5 km/s is only detected toward the MP2 position, most likely related to a low-UV irradiated PDR. We derived the column density of all the species, and determined the deuterium fractions (Dfrac). The values of Dfrac are around 0.01 for all the observed species, except for HCO+ and N2H+ which have values 10 times lower. The values found in Mon R2 are well explained with pseudo-time-dependent gas-phase model in which deuteration occurs mainly via ion-molecule reactions with H2D+, CH2D+ and C2HD+. Finally, the [H13CN]/[HN13C] ratio is very high (~11) for the 10 km/s component, which also agree with our model predictions for an age of ~0.01-0.1 Myr. The deuterium chemistry is a good tool for studying star-forming regions. The low-mass star-forming regions seem well characterized with Dfrac(N2H+) or Dfrac(HCO+), but it is required a complete chemical modeling to date massive star-forming regions, because the higher gas temperature together with the rapid evolution of massive protostars., Comment: 14 pages of manuscript, 17 pages of apendix, 7 figures in the main text, accepted for publication in A&A

Published
2014
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20. The IRAM-30 m line survey of the Horsehead PDR. IV. Comparative chemistry of H2CO and CH3OH

Author

Maryvonne Gerin, J. R. Goicoechea, Viviana V. Guzmán, E. Roueff, F. Le Petit, J. Pety, Pierre Gratier, J. Le Bourlot, A. Faure, Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Ctr Astrobiol CSIC INTA, Lab Astofis Mol, Madrid 28850, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), 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), Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, École normale supérieure - Paris (ENS 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), Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
Hydrogen, Thermal desorption, FOS: Physical sciences, chemistry.chemical_element, Astrophysics, 01 natural sciences, ISM: clouds, law.invention, Telescope, Abundance (ecology), law, photon-dominated region (PDR), 0103 physical sciences, 010303 astronomy & astrophysics, Line (formation), Envelope (waves), Physics, radio lines: ISM, 010308 nuclear & particles physics, astrochemistry, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, ISM: molecules, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], chemistry, 13. Climate action, Space and Planetary Science, radiative transfer, Astrophysics of Galaxies (astro-ph.GA), [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Dense core
Abstract

Aims. We investigate the dominant formation mechanism of H2CO and CH3OH in the Horsehead PDR and its associated dense core. Methods. We performed deep integrations of several H2CO and CH3OH lines at two positions in the Horsehead, namely the PDR and dense core, with the IRAM-30m telescope. In addition, we observed one H2CO higher frequency line with the CSO telescope at both positions. We determine the H2CO and CH3OH column densities and abundances from the single-dish observations complemented with IRAM-PdBI high-angular resolution maps (6") of both species. We compare the observed abundances with PDR models including either pure gas-phase chemistry or both gas-phase and grain surface chemistry. Results. We derive CH3OH abundances relative to total number of hydrogen atoms of ~1.2e-10 and ~2.3e-10 in the PDR and dense core positions, respectively. These abundances are similar to the inferred H2CO abundance in both positions (~2e-10). We find an abundance ratio H2CO/CH3OH of ~2 in the PDR and ~1 in the dense core. Pure gas-phase models cannot reproduce the observed abundances of either H2CO or CH3OH at the PDR position. Both species are therefore formed on the surface of dust grains and are subsequently photodesorbed into the gas-phase at this position. At the dense core, on the other hand, photodesorption of ices is needed to explain the observed abundance of CH3OH, while a pure gas-phase model can reproduce the observed H2CO abundance. The high-resolution observations show that CH3OH is depleted onto grains at the dense core. CH3OH is thus present in an envelope around this position, while H2CO is present in both the envelope and the dense core itself. Conclusions. Photodesorption is an efficient mechanism to release complex molecules in low FUV-illuminated PDRs, where thermal desorption of ice mantles is ineffective., 12 pages, 5 tables, 7 figures; Accepted for publication in A&A

Published
2013
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21. The IRAM-30 m line survey of the Horsehead PDR. III. High abundance of complex (iso-)nitrile molecules in UV-illuminated gas

Author

Pierre Gratier, J. Pety, A. Faure, J. R. Goicoechea, Maryvonne Gerin, E. Roueff, Viviana V. Guzmán, Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), 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), Ctr Astrobiol CSIC INTA, Lab Astofis Mol, Madrid 28850, Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS 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), Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)

Subjects
Nitrile, FOS: Physical sciences, Astrophysics, Electron, 010402 general chemistry, 01 natural sciences, ISM: clouds, chemistry.chemical_compound, Atmospheric radiative transfer codes, 0103 physical sciences, 010303 astronomy & astrophysics, Hyperfine structure, Line (formation), Physics, astrochemistry, ISM: individual objects: Horsehead, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy, ISM: molecules, 0104 chemical sciences, Wavelength, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], chemistry, 13. Climate action, Space and Planetary Science, Electron excitation, radiative transfer, Astrophysics of Galaxies (astro-ph.GA), [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract

Complex (iso-)nitrile molecules, such as CH3CN and HC3N, are relatively easily detected in our Galaxy and in other galaxies. We constrain their chemistry through observations of two positions in the Horsehead edge: the photo-dissociation region (PDR) and the dense, cold, and UV-shielded core just behind it. We systematically searched for lines of CH3CN, HC3N, C3N, and some of their isomers in our sensitive unbiased line survey at 3, 2, and 1mm. We derived column densities and abundances through Bayesian analysis using a large velocity gradient radiative transfer model. We report the first clear detection of CH3NC at millimeter wavelength. We detected 17 lines of CH3CN at the PDR and 6 at the dense core position, and we resolved its hyperfine structure for 3 lines. We detected 4 lines of HC3N, and C3N is clearly detected at the PDR position. We computed new electron collisional rate coefficients for CH3CN, and we found that including electron excitation reduces the derived column density by 40% at the PDR position. While CH3CN is 30 times more abundant in the PDR than in the dense core, HC3N has similar abundance at both positions. The isomeric ratio CH3NC/CH3CN is 0.15+-0.02. In the case of CH3CN, pure gas phase chemistry cannot reproduce the amount of CH3CN observed in the UV-illuminated gas. We propose that CH3CN gas phase abundance is enhanced when ice mantles of grains are destroyed through photo-desorption or thermal-evaporation in PDRs, and through sputtering in shocks. (abridged), Accepted for publication in Astronomy & Astrophysics

Published
2013
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22. Limits on chemical complexity in diffuse clouds: search for CH3OH and HC5N absorption (Corrigendum)

Author

J. Pety, R. Lucas, Harvey S. Liszt, National Radio Astronomy Observatory, Charlottesville (NRAO), Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Instrumentation et télédétection, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), and Dynamique des milieux interstellaires et plasmas stellaires

Subjects
Physics, Astrochemistry, Space and Planetary Science, Astronomy and Astrophysics, Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Absorption (electromagnetic radiation)
Abstract

International audience; Not Available

Published
2016
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23. Physics and chemistry of UV illuminated gas: the Horsehead case

Author

Pierre Gratier, J. R. Goicoechea, M. Gerin, E. Roueff, D. Teyssier, J. Pety, Viviana V. Guzmán, Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), AMOR 2015, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), 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), École normale supérieure - Paris (ENS-PSL), 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), 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), Consejo Superior de Investigaciones Científicas [Spain] (CSIC), and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Astrochemistry, 010504 meteorology & atmospheric sciences, [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Analytical chemistry, Astronomy and Astrophysics, Observable, Astrophysics, 01 natural sciences, Galaxy, law.invention, Telescope, 13. Climate action, Space and Planetary Science, law, 0103 physical sciences, Thermal, Molecule, Isotopologue, 010303 astronomy & astrophysics, Hyperfine structure, 0105 earth and related environmental sciences
Abstract

Molecular lines are used to trace the physical conditions of the gas in different environments, from high-z galaxies to proto-planetary disks. To fully benefit from the diagnostic power of the molecular lines, the formation and destruction paths of the molecules must be quantitatively understood. This is challenging because the physical conditions are extreme and the dynamic plays an important role. In this context the PDR of the Horsehead mane is a particularly interesting case because the geometry is simple (almost 1D, viewed edge-on; Abergel et al.2003), the density profile is well constrained and we are making several efforts to constrain the thermal profile. The combination of small distance to Earth (at 400 pc, 1″ corresponds to 0.002 pc), low illumination (χ = 60) and high density (nH ~ 105 cm−3) implies that all the interesting physical and chemical processes can be probed in a field-of-view of less than 50″ (with typical spatial scales ranging between 1″ and 10″). Hence, the Horsehead PDR is a good source to benchmark the physics and chemistry of UV illuminated neutral gas.In our recent work on the ISM physics and chemistry in the Horsehead we have shown the importance of the interplay between the solid and gas phase chemistry in the formation of (complex) organic molecules, like H2CO, CH3OH and CH3CN, which reveal that photo-desorption of ices is an efficient mechanism to release molecules into the gas phase (Guzmán et al.2011, Gratier et al. in prep, Guzman et al. in prep)}. We have also provided new diagnostics of the UV illuminated matter. For example, we detected CF+ and resolved its hyperfine structure (Guzman et al.2012b). We propose that CF+, which is observable from the ground, can be used as a proxy of C+ (Guzman et al.2012). Finally, we reported the first detection of the small hydrocarbon C3H+, which sheds light on the formation pathways of other observed small hydrocarbons, like C3H and C3H2 ((Pety et al. 2012). Part of these results were possible thanks to a complete an unbiased line survey at 1, 2 and 3 mm performed with the IRAM-30m telescope (Horsehead WHISPER), where approximately 30 species (plus their isotopologues) are detected.

Published
2012
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24. Herschel/HIFI observations of CO, H2O and NH3 in Monoceros R2

Author

C. Kramer, J. Le Bourlot, J. Montillaud, F. Le Petit, Volker Ossenkopf, M. González-García, C. Joblin, O. Berne, Maryvonne Gerin, P. Pilleri, J. Pety, José Cernicharo, A. Fuente, J. R. Rizzo, J. R. Goicoechea, Los Alamos National Laboratory (LANL), Observatorio Astronómico Nacional (OAN), oan, Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Physikalisches Institut [Köln], Universität zu Köln, Univ Toulouse UPS, Ctr Etud Spatiale Rayonnements, F-31062 Toulouse 9, France, Centre Etud Spatiale Rayonnements Toulouse, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Paris (OP), 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), Department of Physics [Helsinki], Falculty of Science [Helsinki], University of Helsinki-University of Helsinki, Instituto de Radio Astronomía Milimétrica, Laboratoire Univers et Théories (LUTH (UMR_8102)), 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), Observatorio Astronomico Nacional, Madrid, Universität zu Köln = University of Cologne, Centre d'étude spatiale des rayonnements (CESR), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Helsingin yliopisto = Helsingfors universitet = University of Helsinki-Helsingin yliopisto = Helsingfors universitet = University of Helsinki, 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), Ctr Astrobiol CSIC INTA, Lab Astrofis Mol, Madrid 28850, Spain, Ctr Astrobiol CSIC INTA, Lab Astrofis Mol, Madrid, 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), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Brightness, HII regions, ISM: individual objects: Mon R2, 010504 meteorology & atmospheric sciences, ISM: structure, FOS: Physical sciences, Context (language use), Astrophysics, Spatial distribution, 01 natural sciences, Atmospheric radiative transfer codes, Abundance (ecology), photon-dominated region (PDR), 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Line (formation), Physics, Velocity gradient, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, ISM: molecules, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), submillimeter: ISM, Outflow, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract

Context. Mon R2 is the only ultracompact HII region (UCHII) where the associated photon-dominated region (PDR) can be resolved with Herschel. Due to its brightness and proximity, it is the best source to investigate the chemistry and physics of highly UV-irradiated PDRs. Aims. Our goal is to estimate the abundance of H2O and NH3 in this region and investigate their origin. Methods. We present new observations obtained with HIFI and the IRAM-30m telescope. Using a large velocity gradient approach, we model the line intensities and derive an average abundance of H2O and NH3 across the region. Finally, we model the line profiles with a non-local radiative transfer model and compare these results with the abundance predicted by the Meudon PDR code. Results. The variations of the line profiles and intensities indicate complex geometrical and kinematical patterns. The H2O lines present a strong absorption at the ambient velocity and emission in high velocity wings towards the HII region. The spatial distribution of the o-H2^18O line shows that the its emission arises in the PDR surrounding the HII region. By modeling the o-H2^18O emission we derive a mean abundance of o-H2O of ~10^-8 relative to H2. The ortho-H2O abundance is however larger, ~1x10^-7, in the high velocity wings. Possible explanations for this larger abundance include an expanding hot PDR and/or an outflow. Ammonia seems to be present only in the envelope with an average abundance of ~2x10^-9 relative to H2. Conclusions. The Meudon PDR code can account for the measured water abundance in the high velocity gas as long as we assume that it originates from a, 12 pages, 7 figures, 3 tables. Accepted for publication in A&A. Abstract shortened. Updated references, language editing applied in v2

Published
2012
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25. Imaging galactic diffuse clouds: CO emission, reddening and turbulent flow in the gas around Zeta Oph

Author

K. Tachihara, Harvey S. Liszt, J. Pety, National Radio Astronomy Observatory (NRAO), Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Paris (OP), 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), and National Astronomical Observatory of Japan (NAOJ)

Subjects
Physics, 010504 meteorology & atmospheric sciences, Mean kinetic temperature, Turbulence, astrochemistry, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, ISM: clouds, Astrophysics - Astrophysics of Galaxies, Spectral line, ISM: molecules, Stars, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Supersonic speed, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Absorption (chemistry), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Line (formation)
Abstract

Methods: 12CO emission is imaged in position and position-velocity space analyzed statistically, and then compared with maps of total reddening and with models of the C+ - CO transition in H2-bearing diffuse clouds. Results: Around Zeta Oph, 12CO emission appears in two distinct intervals of reddening centered near EBV = 0.4 and 0.65 mag, of which < 0.2 mag is background material. Within either interval, the integrated 12CO intensity varies up to 6-12 K-km/s compared to 1.5 K-km/s toward Zeta Oph. Nearly 80% of the individual profiles have velocity dispersions < 0.6 km/s, which are subsonic at the kinetic temperature derived from H2 toward Zeta Oph, 55 K. Partly as a result, 12CO emission exposes the internal, turbulent, supersonic (1-3 km/s) gas flows with especial clarity in the cores of strong lines. The flows are manifested as resolved velocity gradients in narrow, subsonically-broadened line cores. Conclusions: The scatter between N(CO) and EBV in global, CO absorption line surveys toward bright stars is present in the gas seen around Zeta Oph, reflecting the extreme sensitivity of N(12CO) to ambient conditions. The two-component nature of the optical absorption toward Zeta Oph is coincidental and the star is occulted by a single body of gas with a complex internal structure, not by two distinct clouds. The very bright 12CO lines in diffuse gas arise at N(H2) ~ 10^21/cm^2 in regions of modest density n(H) ~ 200-500/cc and somewhat more complete C+-CO conversion. Given the variety of structure in the foreground gas, it is apparent that only large surveys of absorption sightlines can hope to capture the intrinsic behavior of diffuse gas., 2009 A&A, in press

Published
2009
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26. Biopolymers: Multidimensional Vascularized Polymers using Degradable Sacrificial Templates (Adv. Funct. Mater. 7/2015)

Author

Nancy R. Sottos, Jeffrey S. Moore, Coppola Anthony M, Stephen J. Pety, Thu Q. Doan, Ryan C. R. Gergely, Piyush R. Thakre, Brett P. Krull, Scott R. White, and Jason F. Patrick

Subjects
Biomaterials, chemistry.chemical_classification, Template, Materials science, chemistry, Microfluidics, Electrochemistry, Nanotechnology, Polymer, Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Published
2015
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27. First detection of [N II] 205μm absorption in interstellar gas

Author

J. R. Goicoechea, Michael Olberg, Maryvonne Gerin, G. E. Hassel, François Levrier, John H. Black, Bhaswati Mookerjea, J. Pety, E. Falgarone, Karl M. Menten, Carina M. Persson, Ministerio de Ciencia e Innovación (España), Ministerio de Economía y Competitividad (España), and Swedish National Space Board

Subjects
Proton, ISM: structure, Astrophysics, ISM: atoms, 01 natural sciences, Molecular physics, ISM: abundances, Spectral line, Micrometre, 0103 physical sciences, Emission spectrum, Spectral resolution, 010306 general physics, Absorption (electromagnetic radiation), Galaxy: general, 010303 astronomy & astrophysics, general [Galaxy], Line (formation), abundances [ISM], Physics, Line: formation, Astronomy and Astrophysics, Atomic processes, Galactic plane, atoms [ISM], Space and Planetary Science, formation [Line], structure [ISM]
Abstract

We present high resolution [N ii] 205 μm (3P 1-3P0) spectra obtained with Herschel-HIFI towards a small sample of far-infrared bright star forming regions in the Galactic plane: W 31C (G10.6-0.4), W 49N (G43.2-0.1), W 51 (G49.5-0.4), and G34.3+0.1. All sources display an emission line profile associated directly with the H ii regions themselves. For the first time we also detect absorption of the [N ii] 205 μm line by extended low-density foreground material towards W 31C and W 49N over a wide range of velocities. We attribute this absorption to the warm ionised medium (WIM) and find N(N+) ≈ 1.5 × 10 17 cm-2 towards both sources. This is in agreement with recent Herschel-HIFI observations of [C ii] 158 μm, also observed in absorption in the same sight-lines, if ≈ 7-10% of all C+ ions exist in the WIM on average. Using an abundance ratio of [N]/[H] = 6.76 × 10-5 in the gas phase we find that the mean electron and proton volume densities are ~0.1-0.3 cm-3 assuming a WIM volume filling fraction of 0.1-0.4 with a corresponding line-of-sight filling fraction of 0.46-0.74. A low density and a high WIM filling fraction are also supported by RADEX modelling of the [N ii] 205 μm absorption and emission together with visible emission lines attributed mainly to the WIM. The detection of the 205 μm line in absorption emphasises the importance of a high spectral resolution, and also offers a new tool for investigation of the WIM., C.M.P. and J.H.B. acknowledge generous support from the Swedish National Space Board. J.R.G. thanks the Spanish MINECO for funding support under grants CSD2009-00038, AYA2009-07304 and AYA2012-32032.

Published
2014
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28. Gas inflow and AGN-driven outflow in M51

Author

Santiago García-Burillo, Eva Schinnerer, Frank Bigiel, J. Pety, Kathryn Kreckel, Guillermo A. Blanc, Miguel Querejeta, Annie Hughes, David S. Meier, and Sharon E. Meidt

Subjects
Gravitation, Physics, medicine.anatomical_structure, Distribution (number theory), Space and Planetary Science, medicine, Astronomy and Astrophysics, Outflow, Inflow, Mechanics, Nucleus
Abstract

We study the feeding and feedback of the nucleus of M51 by considering gravitational torques, responsible for gas inflow, in relation to the local distribution of dense gas.

Published
2014
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29. A 850-GHz waveguide receiver employing a niobium SIS junction fabricated on a 1-μm Si_3N_4 membrane

Author

P. L. Schaffer, Jacob Kooi, Thomas G. Phillips, Christopher K. Walker, Henry G. LeDuc, B. Bumble, and J. Pety

Subjects
Heterodyne, Noise temperature, Radiation, Materials science, Sideband, business.industry, Superheterodyne receiver, Electrical engineering, Niobium, chemistry.chemical_element, Condensed Matter Physics, law.invention, chemistry, Tunnel junction, law, Optoelectronics, Electrical and Electronic Engineering, business, Current density, Noise (radio)
Abstract

We report on a 850-GHz superconducting-insulator-superconducting (SIS) heterodyne receiver employing an RF-tuned niobium tunnel junction with a current density of 14 kA/cm/sup 2/, fabricated on a 1-/spl mu/m Si/sub 3/N/sub 4/ supporting membrane. Since the mixer is designed to be operated well above the superconducting gap frequency of niobium (2/spl Delta//h/spl ap/690 GHz), special care has been taken to minimize niobium transmission-line losses. Both Fourier transform spectrometer (FTS) measurements of the direct detection performance and calculations of the IF output noise with the mixer operating in heterodyne mode, indicate an absorption loss in the niobium film of about 6.8 dB at 822 GHz. These results are in reasonably good agreement with the loss predicted by the Mattis-Bardeen theory in the extreme anomalous limit. From 800 to 830 GHz, we report uncorrected receiver noise temperatures of 518 or 514 K when we use Callen and Welton's law to calculate the input load temperatures. Over the same frequency range, the mixer has a 4-dB conversion loss and 265 K/spl plusmn/10 K noise temperature. At 890 GHz, the sensitivity of the receiver has degraded to 900 K, which is primarily the result of increased niobium film loss in the RF matching network. When the mixer was cooled from 4.2 to 1.9 K, the receiver noise temperature improved about 20% 409-K double sideband (DSB). Approximately half of the receiver noise temperature improvement can be attributed to a lower mixer conversion loss, while the remainder is due to a reduction in the niobium film absorption loss. At 982 GHz, we measured a receiver noise temperature of 1916 K.

Published
1998

30. Millimeter-wave Observations of Polyatomic Molecules in Diffuse Clouds

Author

J. Pety, Harvey S. Liszt, and R. Lucas

Subjects
Physics, Space and Planetary Science, Extremely high frequency, Polyatomic ion, Astronomy, Molecule, Astronomy and Astrophysics, Astrophysics, Absorption (chemistry)
Abstract

Millimeter-wave (mm-wave) absorption profiles toward extragalactic sources consistently find just diffuse (occasionally perhaps translucent) neutral gas—low/moderate density and extinction—along even some very long, dark lines of sight. CO, often heavily fractionated and mimicking the appearance of dark gas in emission, occasionally absent in emission even when present in absorption, is not the dominant form of carbon in these regions (presumably it is C) yet the abundances of many other molecules resemble those seen in TMC-1. Some species (OH, HCO, C2H and C3H2) turn on with high abundances just when H2 does; others (HCN, HNC, CN) require slightly higher N (H2) and yet others (CS and other sulfur-bearing species, NH3 and H2CO) even higher N (H2). The systematics and implications of these recent discoveries are discussed here.

Published
2006
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31. Carbon Chemistry in Photodissociation Regions

Author

Evelyne Roueff, D. Teyssier, D. Fossé, Javier R. Goicoechea, J. Pety, Christine Joblin, Maryvonne Gerin, A. Abergel, and J. Le Bourlot

Subjects
Physics, Carbon chain, Interstellar medium, chemistry, Space and Planetary Science, Abundance (ecology), Carbon chemistry, Photodissociation, chemistry.chemical_element, Astronomy and Astrophysics, Astrophysics, Spatial distribution, Carbon
Abstract

We present recent results on the carbon chemistry in photodissociation regions. We show that carbon chains and rings (CCH, c-C $_3$ H $_2$ and C $_4$ H) are tightly spatially correlated with each other, and with the mid-infrared emission due to PAHs (7 and 15 $\mu$ m), mapped by ISOCAM. Neither the spatial distribution, nor the abundances of these species can be fit by state-of-the-art PDR models, which calls for another production mechanism. We discuss model predictions for carbon clusters and simple hydrocarbons. We show how selected abundance ratios can be used as a diagnostic of the physical conditions. We stress the need for more theoretical and laboratory work on fundamental processes relevant for the interstellar medium, which should be taken into account in the astrochemical models, but whose rates are not known accurately enough.

Published
2006
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32. Mapping Metallicity Variations across Nearby Galaxy Disks.

Author

K. Kreckel, I.-T. Ho, G. A. Blanc, B. Groves, F. Santoro, E. Schinnerer, F. Bigiel, M. Chevance, E. Congiu, E. Emsellem, C. Faesi, S. C. O. Glover, K. Grasha, J. M. D. Kruijssen, P. Lang, A. K. Leroy, S. E. Meidt, R. McElroy, J. Pety, and E. Rosolowsky

Subjects
DISK galaxies, INTEGRAL field spectroscopy, VERY large telescopes, SPIRAL galaxies, STAR clusters, MOLECULAR clouds, INTERSTELLAR medium
Abstract

The distribution of metals within a galaxy traces the baryon cycle and the buildup of galactic disks, but the detailed gas phase metallicity distribution remains poorly sampled. We have determined the gas phase oxygen abundances for 7138 H ii regions across the disks of eight nearby galaxies using Very Large Telescope/Multi Unit Spectroscopic Explorer (MUSE) optical integral field spectroscopy as part of the PHANGS–MUSE survey. After removing the first-order radial gradients present in each galaxy, we look at the statistics of the metallicity offset (ΔO/H) and explore azimuthal variations. Across each galaxy, we find low (σ = 0.03–0.05 dex) scatter at any given radius, indicative of efficient mixing. We compare physical parameters for those H ii regions that are 1σ outliers toward both enhanced and reduced abundances. Regions with enhanced abundances have high ionization parameter, higher Hα luminosity, lower Hα velocity dispersion, younger star clusters, and associated molecular gas clouds showing higher molecular gas densities. This indicates recent star formation has locally enriched the material. Regions with reduced abundances show increased Hα velocity dispersions, suggestive of mixing introducing more pristine material. We observe subtle azimuthal variations in half of the sample, but cannot always cleanly associate this with the spiral pattern. Regions with enhanced and reduced abundances are found distributed throughout the disk, and in half of our galaxies we can identify subsections of spiral arms with clearly associated metallicity gradients. This suggests spiral arms play a role in organizing and mixing the interstellar medium. [ABSTRACT FROM AUTHOR]

Published
2019
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33. EMPIRE: The IRAM 30 m Dense Gas Survey of Nearby Galaxies.

Author

María J. Jiménez-Donaire, F. Bigiel, A. K. Leroy, A. Usero, D. Cormier, J. Puschnig, M. Gallagher, A. Kepley, A. Bolatto, S. García-Burillo, A. Hughes, C. Kramer, J. Pety, E. Schinnerer, A. Schruba, K. Schuster, and F. Walter

Subjects
SPIRAL galaxies, MILKY Way, GAS distribution, DISK galaxies, TRACE gases, STAR formation
Abstract

We present EMPIRE, an IRAM 30 m large program that mapped λ = 3–4 mm dense gas tracers at ∼1–2 kpc resolution across the whole star-forming disk of nine nearby massive spiral galaxies. We describe the EMPIRE observing and reduction strategies and show new whole-galaxy maps of HCN(1−0), HCO+(1−0), HNC(1−0), and CO(1−0). We explore how the HCN-to-CO and IR-to-HCN ratios, observational proxies for the dense gas fraction and dense gas star formation efficiency, depend on host galaxy and local environment. We find that the fraction of dense gas correlates with stellar surface density, gas surface density, molecular-to-atomic gas ratio, and dynamical equilibrium pressure. In EMPIRE, the star formation rate per unit dense gas is anticorrelated with these same environmental parameters. Thus, although dense gas appears abundant in the central regions of many spiral galaxies, this gas appears relatively inefficient at forming stars. These results qualitatively agree with previous work on nearby galaxies and the Milky Way’s Central Molecular Zone. To first order, EMPIRE demonstrates that the conditions in a galaxy disk set the gas density distribution and that the dense gas traced by HCN shows an environment-dependent relation to star formation. However, our results also show significant (±0.2 dex) galaxy-to-galaxy variations. We suggest that gas structure below the scale of our observations and dynamical effects likely also play an important role. [ABSTRACT FROM AUTHOR]

Published
2019
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34. Stellar structures, molecular gas, and star formation across the PHANGS sample of nearby galaxies

Author

M. Querejeta, E. Schinnerer, S. Meidt, J. Sun, A. K. Leroy, E. Emsellem, R. S. Klessen, J. C. Muñoz-Mateos, H. Salo, E. Laurikainen, I. Bešlić, G. A. Blanc, M. Chevance, D. A. Dale, C. Eibensteiner, C. Faesi, A. García-Rodríguez, S. C. O. Glover, K. Grasha, J. Henshaw, C. Herrera, A. Hughes, K. Kreckel, J. M. D. Kruijssen, D. Liu, E. J. Murphy, H.-A. Pan, J. Pety, A. Razza, E. Rosolowsky, T. Saito, A. Schruba, A. Usero, E. J. Watkins, T. G. Williams, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and 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)

Subjects
EDGE-CALIFA SURVEY, DEPLETION TIME, FORMATION EFFICIENCY, SPIRAL ARMS, FOS: Physical sciences, MORPHOLOGICAL CLASSIFICATIONS, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 33 GHZ OBSERVATIONS, Astrophysics::Solar and Stellar Astrophysics, FORMATION LAW, Astrophysics::Galaxy Astrophysics, Physics, ISM [galaxies], [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Star formation, 100 PC SCALES, SPITZER SURVEY, Astronomy and Astrophysics, Sample (graphics), Astrophysics - Astrophysics of Galaxies, Galaxy, Physics and Astronomy, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), galaxies: star formation, structure [galaxies], galaxies: structure, Astrophysics::Earth and Planetary Astrophysics, star formation [galaxies], BARRED GALAXIES, galaxies: ISM
Abstract

We identify stellar structures in the PHANGS sample of 74 nearby galaxies and construct morphological masks of sub-galactic environments based on Spitzer 3.6 micron images. At the simplest level, we distinguish centres, bars, spiral arms, interarm and discs without strong spirals. Slightly more sophisticated masks include rings and lenses, publicly released but not explicitly used in this paper. We examine trends using PHANGS-ALMA CO(2-1) intensity maps and tracers of star formation. The interarm regions and discs without strong spirals dominate in area, whereas molecular gas and star formation are quite evenly distributed among the five basic environments. We reproduce the molecular Kennicutt-Schmidt relation with a slope compatible with unity within the uncertainties, without significant slope differences among environments. In contrast to early studies, we find that bars are not always deserts devoid of gas and star formation, but instead they show large diversity. Similarly, spiral arms do not account for most of the gas and star formation in disc galaxies, and they do not have shorter depletion times than the interarm regions. Spiral arms accumulate gas and star formation, without systematically boosting the star formation efficiency. Centres harbour remarkably high surface densities and on average shorter depletion times than other environments. Centres of barred galaxies show higher surface densities and wider distributions compared to the outer disc; yet, depletion times are similar to unbarred galaxies, suggesting highly intermittent periods of star formation when bars episodically drive gas inflow, without enhancing the central star formation efficiency permanently. In conclusion, we provide quantitative evidence that stellar structures in galaxies strongly affect the organisation of molecular gas and star formation, but their impact on star formation efficiency is more subtle., 28 pages, 11 figures, accepted for publication in A&A

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37. In situ spheroid formation in distant submillimetre-bright galaxies.

Author

Tan QH, Daddi E, Magnelli B, Correa CA, Bournaud F, Adscheid S, Zhang SB, Elbaz D, Gómez-Guijarro C, Kalita BS, Liu D, Liu Z, Pety J, Puglisi A, Schinnerer E, Silverman JD, and Valentino F

Abstract

Most stars in today's Universe reside within spheroids, which are bulges of spiral galaxies and elliptical galaxies 1,2 . Their formation is still an unsolved problem 3-5 . Infrared/submillimetre-bright galaxies at high redshifts 6 have long been suspected to be related to spheroid formation 7-12 . Proving this connection has been hampered so far by heavy dust obscuration when focusing on their stellar emission 13-15 or by methodologies and limited signal-to-noise ratios when looking at submillimetre wavelengths 16,17 . Here we show that spheroids are directly generated by star formation within the cores of highly luminous starburst galaxies in the distant Universe. This follows from the ALMA submillimetre surface brightness profiles, which deviate substantially from those of exponential disks, and from the skewed-high axis-ratio distribution. Most of these galaxies are fully triaxial rather than flat disks: the ratio of the shortest to the longest of their three axes is half, on average, and increases with spatial compactness. These observations, supported by simulations, reveal a cosmologically relevant pathway for in situ spheroid formation through starbursts that is probably preferentially triggered by interactions (and mergers) acting on galaxies fed by non-coplanar gas accretion streams., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Published
2024
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38. Abundances of sulphur molecules in the Horsehead nebula First NS + detection in a photodissociation region.

Author

Rivière-Marichalar P, Fuente A, Goicoechea JR, Pety J, Le Gal R, Gratier P, Guzmán V, Roueff E, Loison JC, Wakelam V, and Gerin M

Abstract

Context: Sulphur is one of the most abundant elements in the Universe (S/H ∼ 1.3 × 10 -5 ) and plays a crucial role in biological systems on Earth. The understanding of its chemistry is therefore of major importance., Aims: Our goal is to complete the inventory of S-bearing molecules and their abundances in the prototypical photodissociation region (PDR) the Horsehead nebula to gain insight into sulphur chemistry in UV irradiated regions. Based on the WHISPER (Wide-band High-resolution Iram-30m Surveys at two positions with Emir Receivers) millimeter (mm) line survey, our goal is to provide an improved and more accurate description of sulphur species and their abundances towards the core and PDR positions in the Horsehead., Methods: The Monte Carlo Markov Chain (MCMC) methodology and the molecular excitation and radiative transfer code RADEX were used to explore the parameter space and determine physical conditions and beam-averaged molecular abundances., Results: A total of 13 S-bearing species (CS, SO, SO 2 , OCS, H 2 CS - both ortho and para - HDCS, C 2 S, HCS + , SO + , H 2 S, S 2 H, NS and NS + ) have been detected in the two targeted positions. This is the first detection of SO + in the Horsehead and the first detection of NS + in any PDR. We find a differentiated chemical behaviour between C-S and O-S bearing species within the nebula. The C-S bearing species C 2 S and o-H 2 CS present fractional abundances a factor of > two higher in the core than in the PDR. In contrast, the O-S bearing molecules SO, SO 2 , and OCS present similar abundances towards both positions. A few molecules, SO + , NS, and NS + , are more abundant towards the PDR than towards the core, and could be considered as PDR tracers., Conclusions: This is the first complete study of S-bearing species towards a PDR. Our study shows that CS, SO, and H 2 S are the most abundant S-bearing molecules in the PDR with abundances of ∼ a few 10 -9 . We recall that SH, SH + , S, and S + are not observable at the wavelengths covered by the WHISPER survey. At the spatial scale of our observations, the total abundance of S atoms locked in the detected species is < 10 -8 , only ∼0.1% of the cosmic sulphur abundance.

Published
2019
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39. Oxygen fractionation in dense molecular clouds.

Author

Loison JC, Wakelam V, Gratier P, Hickson KM, Bacmann A, Agùndez M, Marcelino N, Cernicharo J, Guzman V, Gerin M, Goicoechea JR, Roueff E, Le Petit F, Pety J, Fuente A, and Riviere-Marichalar P

Abstract

We have developed the first gas-grain chemical model for oxygen fractionation (also including sulphur fractionation) in dense molecular clouds, demonstrating that gas-phase chemistry generates variable oxygen fractionation levels, with a particularly strong effect for NO, SO, O 2 , and SO 2 . This large effect is due to the efficiency of the neutral 18 O + NO, 18 O + SO, and 18 O + O 2 exchange reactions. The modeling results were compared to new and existing observed isotopic ratios in a selection of cold cores. The good agreement between model and observations requires that the gas-phase abundance of neutral oxygen atoms is large in the observed regions. The S 16 O/S 18 O ratio is predicted to vary substantially over time showing that it can be used as a sensitive chemical proxy for matter evolution in dense molecular clouds.

Published
2019
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40. ALMA observations of the young protostellar system Barnard 1b: signatures of an incipient hot corino in B1b-S.

Author

Marcelino N, Gerin M, Cernicharo J, Fuente A, Wootten HA, Chapillon E, Pety J, Lis DC, Roueff E, Commerçon B, and Ciardi A

Abstract

The Barnard 1b core shows signatures of being at the earliest stages of low-mass star formation, with two extremely young and deeply embedded protostellar objects. Hence, this core is an ideal target to study the structure and chemistry of the first objects formed in the collapse of prestellar cores. We present ALMA Band 6 spectral line observations at ~0.6″ of angular resolution towards Barnard 1b. We have extracted the spectra towards both protostars, and used a Local Thermodynamic Equilibrium (LTE) model to reproduce the observed line profiles. B1b-S shows rich and complex spectra, with emission from high energy transitions of complex molecules, such as CH 3 OCOH and CH 3 CHO, including vibrational level transitions. We have tentatively detected for the first time in this source emission from NH 2 CN, NH 2 CHO, CH 3 CH 2 OH, CH 2 OHCHO, CH 3 CH 2 OCOH and both aGg ' and gGg ' conformers of (CH 2 OH) 2 . This is the first detection of ethyl formate (CH 3 CH 2 OCOH) towards a low-mass star forming region. On the other hand, the spectra of the FHSC candidate B1b-N are free of COMs emission. In order to fit the observed line profiles in B1b-S, we used a source model with two components: an inner hot and compact component (200 K, 0.35″) and an outer and colder one (60 K, 0.6″). The resulting COM abundances in B1b-S range from 10 -13 for NH 2 CN and NH 2 CHO, up to 10 -9 for CH 3 OCOH. Our ALMA Band 6 observations reveal the presence of a compact and hot component in B1b-S, with moderate abundances of complex organics. These results indicate that a hot corino is being formed in this very young Class 0 source.

Published
2018
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41. High-speed molecular cloudlets around the Galactic center's supermassive black hole.

Author

Goicoechea JR, Pety J, Chapillon E, Cernicharo J, Gerin M, Herrera C, Requena-Torres MA, and Santa-Maria MG

Abstract

We present 1″-resolution ALMA observations of the circumnuclear disk (CND) and the interstellar environment around Sgr A*. The images unveil the presence of small spatial scale 12 CO ( J =3-2) molecular "cloudlets" (≲20,000 AU size) within the central parsec of the Milky Way, in other words, inside the cavity of the CND, and moving at high speeds, up to 300 km s -1 along the line-of-sight. The 12 CO-emitting structures show intricate morphologies: extended and filamentary at high negative-velocities (v LSR ≲-150 km s -1 ), more localized and clumpy at extreme positive-velocities (v LSR ≳+200 km s -1 ). Based on the pencil-beam 12 CO absorption spectrum toward Sgr A* synchrotron emission, we also present evidence for a diffuse molecular gas component producing absorption features at more extreme negative-velocities (v LSR <-200 km s -1 ). The CND shows a clumpy spatial distribution traced by the optically thin H 13 CN ( J =4-3) emission. Its motion requires a bundle of non-uniformly rotating streams of slightly different inclinations. The inferred gas density peaks, molecular cores of a few 10 5 cm -3 , are lower than the local Roche limit. This supports that CND cores are transient. We apply the two standard orbit models, spirals vs. ellipses, invoked to explain the kinematics of the ionized gas streamers around Sgr A*. The location and velocities of the 12 CO cloudlets inside the cavity are inconsistent with the spiral model, and only two of them are consistent with the Keplerian ellipse model. Most cloudlets, however, show similar velocities that are incompatible with the motions of the ionized streamers or with gas bounded to the central gravity. We speculate that they are leftovers of more massive molecular clouds that fall into the cavity and are tidally disrupted, or that they originate from instabilities in the inner rim of the CND that lead to fragmentation and infall from there. In either case, we show that molecular cloudlets, all together with a mass of several 10 M ⊙ , exist around Sgr A*. Most of them must be short-lived, ≲10 4 yr: photoevaporated by the intense stellar radiation field, G 0 ≃10 5.3 to 10 4.3 , blown away by winds from massive stars in the central cluster, or disrupted by strong gravitational shears.

Published
2018
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42. High-velocity hot CO emission close to Sgr A*: Herschel /HIFI ★ , ★★ submillimeter spectral survey toward Sgr A.

Author

Goicoechea JR, Santa-Maria MG, Teyssier D, Cernicharo J, Gerin M, and Pety J

Abstract

The properties of molecular gas, the fuel that forms stars, inside the cavity of the circumnuclear disk (CND) are not well constrained. We present results of a velocity-resolved submillimeter scan (~480 to 1250 GHz) and [C ii] 158 μ m line observations carried out with Herschel /HIFI toward Sgr A*; these results are complemented by a ~2'×2' 12 CO ( J =3-2) map taken with the IRAM 30 m telescope at ~7″ resolution. We report the presence of high positive-velocity emission (up to about +300 km s -1 ) detected in the wings of 12 CO J =5-4 to 10-9 lines. This wing component is also seen in H 2 O (1 1,0 -1 0,1 ), a tracer of hot molecular gas; in [C ii]158 μ m, an unambiguous tracer of UV radiation; but not in [C i] 492, 806 GHz. This first measurement of the high-velocity 12 CO rotational ladder toward Sgr A* adds more evidence that hot molecular gas exists inside the cavity of the CND, relatively close to the supermassive black hole (< 1 pc). Observed by ALMA, this velocity range appears as a collection of 12 CO ( J =3-2) cloudlets lying in a very harsh environment that is pervaded by intense UV radiation fields, shocks, and affected by strong gravitational shears. We constrain the physical conditions of the high positive-velocity CO gas component by comparing with non-LTE excitation and radiative transfer models. We infer T k ≃400 K to 2000 K for n H ≃(0.2-1.0)·10 5 cm -3 . These results point toward the important role of stellar UV radiation, but we show that radiative heating alone cannot explain the excitation of this ~10-60 M ⊙ component of hot molecular gas inside the central cavity. Instead, strongly irradiated shocks are promising candidates.

Published
2018
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43. Clustering the Orion B giant molecular cloud based on its molecular emission.

Author

Bron E, Daudon C, Pety J, Levrier F, Gerin M, Gratier P, Orkisz JH, Guzman V, Bardeau S, Goicoechea JR, Liszt H, Öberg K, Peretto N, Sievers A, and Tremblin P

Abstract

Context: Previous attempts at segmenting molecular line maps of molecular clouds have focused on using position-position-velocity data cubes of a single molecular line to separate the spatial components of the cloud. In contrast, wide field spectral imaging over a large spectral bandwidth in the (sub)mm domain now allows one to combine multiple molecular tracers to understand the different physical and chemical phases that constitute giant molecular clouds (GMCs)., Aims: We aim at using multiple tracers (sensitive to different physical processes and conditions) to segment a molecular cloud into physically/chemically similar regions (rather than spatially connected components), thus disentangling the different physical/chemical phases present in the cloud., Methods: We use a machine learning clustering method, namely the Meanshift algorithm, to cluster pixels with similar molecular emission, ignoring spatial information. Clusters are defined around each maximum of the multidimensional Probability Density Function (PDF) of the line integrated intensities. Simple radiative transfer models were used to interpret the astrophysical information uncovered by the clustering analysis., Results: A clustering analysis based only on the J = 1 - 0 lines of three isotopologues of CO proves suffcient to reveal distinct density/column density regimes ( n H ~ 100 cm -3 , ~ 500 cm -3 , and > 1000 cm -3 ), closely related to the usual definitions of diffuse, translucent and high-column-density regions. Adding two UV-sensitive tracers, the J = 1 - 0 line of HCO + and the N = 1 - 0 line of CN, allows us to distinguish two clearly distinct chemical regimes, characteristic of UV-illuminated and UV-shielded gas. The UV-illuminated regime shows overbright HCO + and CN emission, which we relate to a photochemical enrichment effect. We also find a tail of high CN/HCO + intensity ratio in UV-illuminated regions. Finer distinctions in density classes ( n H ~ 7 × 10 3 cm -3 ~ 4 × 10 4 cm -3 ) for the densest regions are also identified, likely related to the higher critical density of the CN and HCO + (1 - 0) lines. These distinctions are only possible because the high-density regions are spatially resolved., Conclusions: Molecules are versatile tracers of GMCs because their line intensities bear the signature of the physics and chemistry at play in the gas. The association of simultaneous multi-line, wide-field mapping and powerful machine learning methods such as the Meanshift clustering algorithm reveals how to decode the complex information available in these molecular tracers.

Published
2018
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44. IRC +10 216 in 3-D: morphology of a TP-AGB star envelope.

Author

Guélin M, Patel NA, Bremer M, Cernicharo J, Castro-Carrizo A, Pety J, Fonfría JP, Agúndez M, Santander-García M, Quintana-Lacaci G, Velilla Prieto L, Blundell R, and Thaddeus P

Abstract

During their late pulsating phase, AGB stars expel most of their mass in the form of massive dusty envelopes, an event that largely controls the composition of interstellar matter. The envelopes, however, are distant and opaque to visible and NIR radiation: their structure remains poorly known and the mass-loss process poorly understood. Millimeter-wave interferometry, which combines the advantages of longer wavelength, high angular resolution and very high spectral resolution is the optimal investigative tool for this purpose. Mm waves pass through dust with almost no attenuation. Their spectrum is rich in molecular lines and hosts the fundamental lines of the ubiquitous CO molecule, allowing a tomographic reconstruction of the envelope structure. The circumstellar envelope IRC +10 216 and its central star, the C-rich TP-AGB star closest to the Sun, are the best objects for such an investigation. Two years ago, we reported the first detailed study of the CO(2-1) line emission in that envelope, made with the IRAM 30-m telescope. It revealed a series of dense gas shells, expanding at a uniform radial velocity. The limited resolution of the telescope (HPBW 11″) did not allow us to resolve the shell structure. We now report much higher angular resolution observations of CO(2-1), CO(1-0), CN(2-1) and C 4 H(24-23) made with the SMA, PdB and ALMA interferometers (with synthesized half-power beamwidths of 3″, 1″ and 0.3″, respectively). Although the envelope appears much more intricate at high resolution than with an 11″ beam, its prevailing structure remains a pattern of thin, nearly concentric shells. The average separation between the brightest CO shells is 16″ in the outer envelope, where it appears remarkably constant. Closer to the star (< 40″), the shell pattern is denser and less regular, showing intermediary arcs. Outside the small ( r < 0.3″) dust formation zone, the gas appears to expand radially at a constant velocity, 14.5 km s -1 , with small turbulent motions. Based on that property, we have reconstructed the 3-D structure of the outer envelope and have derived the gas temperature and density radial profiles in the inner ( r < 25″) envelope. The shell-intershell density contrast is found to be typically 3. The over-dense shells have spherical or slightly oblate shapes and typically extend over a few steradians, implying isotropic mass loss. The regular spacing of shells in the outer envelope supports the model of a binary star system with a period of 700 years and a near face-on elliptical orbit. The companion fly-by triggers enhanced episodes of mass loss near periastron. The densification of the shell pattern observed in the central part of the envelope suggests a more complex scenario for the last few thousand years.

Published
2018
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45. First Detection of Interstellar S 2 H.

Author

Fuente A, Goicoechea JR, Pety J, Le Gal R, Martín-Doménech R, Gratier P, Guzmán V, Roueff E, Loison JC, Muñoz Caro GM, Wakelam V, Gerin M, Riviere-Marichalar P, and Vidal T

Abstract

We present the first detection of gas phase S 2 H in the Horsehead, a moderately UV-irradiated nebula. This confirms the presence of doubly sulfuretted species in the interstellar medium and opens a new challenge for sulfur chemistry. The observed S 2 H abundance is ~5×10 -11 , only a factor 4-6 lower than that of the widespread H 2 S molecule. H 2 S and S 2 H are efficiently formed on the UV-irradiated icy grain mantles. We performed ice irradiation experiments to determine the H 2 S and S 2 H photodesorption yields. The obtained values are ~1.2×10 -3 and <1×10 -5 molecules per incident photon for H 2 S and S 2 H, respectively. Our upper limit to the S 2 H photodesorption yield suggests that photo-desorption is not a competitive mechanism to release the S 2 H molecules to the gas phase. Other desorption mechanisms such as chemical desorption, cosmic-ray desorption and grain shattering can increase the gaseous S 2 H abundance to some extent. Alternatively, S 2 H can be formed via gas phase reactions involving gaseous H 2 S and the abundant ions S + and SH + . The detection of S 2 H in this nebula could be therefore the result of the coexistence of an active grain surface chemistry and gaseous photo-chemistry.

Published
2017
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46. Chemical segregation in the young protostars Barnard 1b-N and S Evidence of pseudo-disk rotation in Barnard 1b-S.

Author

Fuente A, Gerin M, Pety J, Commerçon B, Agúndez M, Cernicharo J, Marcelino N, Roueff E, Lis DC, and Wootten HA

Abstract

The extremely young Class 0 object B1b-S and the first hydrostatic core (FSHC) candidate, B1b-N, provide a unique opportunity to study the chemical changes produced in the elusive transition from the prestellar core to the protostellar phase. We present 40"×70" images of Barnard 1b in the 13 CO 1→0, C 18 O 1→0, NH 2 D 1 1,1 a →1 0,1 s , and SO 3 2 →2 1 lines obtained with the NOEMA interferometer. The observed chemical segregation allows us to unveil the physical structure of this young protostellar system down to scales of ∼500 au. The two protostellar objects are embedded in an elongated condensation, with a velocity gradient of ∼0.2-0.4 m s -1 au -1 in the east-west direction, reminiscent of an axial collapse. The NH 2 D data reveal cold and dense pseudo-disks (R∼500-1000 au) around each protostar. Moreover, we observe evidence of pseudo-disk rotation around B1b-S. We do not see any signature of the bipolar outflows associated with B1b-N and B1b-S, which were previously detected in H 2 CO and CH 3 OH, in any of the imaged species. The non-detection of SO constrains the SO/CH 3 OH abundance ratio in the high-velocity gas.

Published
2017
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47. Evidence for disks at an early stage in class 0 protostars?

Author

Gerin M, Pety J, Commerçon B, Fuente A, Cernicharo J, Marcelino N, Ciardi A, Lis DC, Roueff E, Wootten HA, and Chapillon E

Abstract

Aims: The formation epoch of protostellar disks is debated because of the competing roles of rotation, turbulence, and magnetic fields in the early stages of low-mass star formation. Magnetohydrodynamics simulations of collapsing cores predict that rotationally supported disks may form in strongly magnetized cores through ambipolar diffusion or misalignment between the rotation axis and the magnetic field orientation. Detailed studies of individual sources are needed to cross check the theoretical predictions., Methods: We present 0.06 - 0.1 ″ resolution images at 350 GHz toward B1b-N and B1b-S, which are young class 0 protostars, possibly first hydrostatic cores. The images have been obtained with ALMA, and we compare these data with magnetohydrodynamics simulations of a collapsing turbulent and magnetized core., Results: The submillimeter continuum emission is spatially resolved by ALMA. Compact structures with optically thick 350 GHz emission are detected toward both B1b-N and B1b-S, with 0.2 and 0.35″ radii (46 and 80 au at the Perseus distance of 230 pc), within a more extended envelope. The flux ratio between the compact structure and the envelope is lower in B1b-N than in B1b-S, in agreement with its earlier evolutionary status. The size and orientation of the compact structure are consistent with 0.2″ resolution 32 GHz observations obtained with the Very Large Array as a part of the VANDAM survey, suggesting that grains have grown through coagulation. The morphology, temperature, and densities of the compact structures are consistent with those of disks formed in numerical simulations of collapsing cores. Moreover, the properties of B1b-N are consistent with those of a very young protostar, possibly a first hydrostatic core. These observations provide support for the early formation of disks around low-mass protostars.

Published
2017
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48. [Cii] emission from L1630 in the Orion B molecular cloud.

Author

Pabst CHM, Goicoechea JR, Teyssier D, Berné O, Ochsendorf BB, Wolfire MG, Higgins RD, Riquelme D, Risacher C, Pety J, Le Petit F, Roueff E, Bron E, and Tielens AGGM

Abstract

Context: L1630 in the Orion B molecular cloud, which includes the iconic Horsehead Nebula, illuminated by the star system σ Ori, is an example of a photodissociation region (PDR). In PDRs, stellar radiation impinges on the surface of dense material, often a molecular cloud, thereby inducing a complex network of chemical reactions and physical processes., Aims: Observations toward L1630 allow us to study the interplay between stellar radiation and a molecular cloud under relatively benign conditions, that is, intermediate densities and an intermediate UV radiation field. Contrary to the well-studied Orion Molecular Cloud 1 (OMC1), which hosts much harsher conditions, L1630 has little star formation. Our goal is to relate the [Cii] fine-structure line emission to the physical conditions predominant in L1630 and compare it to studies of OMC1., Methods: The [Cii] 158 μ m line emission of L1630 around the Horsehead Nebula, an area of 12' × 17', was observed using the upgraded German Receiver for Astronomy at Terahertz Frequencies (upGREAT) onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA)., Results: Of the [Cii] emission from the mapped area 95%, 13 L ⊙ , originates from the molecular cloud; the adjacent Hii region contributes only 5%, that is, 1 L ⊙ . From comparison with other data (CO(1-0)-line emission, far-infrared (FIR) continuum studies, emission from polycyclic aromatic hydrocarbons (PAHs)), we infer a gas density of the molecular cloud of n H ∼ 3 · 10 3 cm -3 , with surface layers, including the Horsehead Nebula, having a density of up to n H ∼ 4 · 10 4 cm -3 . The temperature of the surface gas is T ∼ 100 K. The average [Cii] cooling efficiency within the molecular cloud is 1.3 · 10 -2 . The fraction of the mass of the molecular cloud within the studied area that is traced by [Cii] is only 8%. Our PDR models are able to reproduce the FIR-[Cii] correlations and also the CO(1-0)-[Cii] correlations. Finally, we compare our results on the heating efficiency of the gas with theoretical studies of photoelectric heating by PAHs, clusters of PAHs, and very small grains, and find the heating efficiency to be lower than theoretically predicted, a continuation of the trend set by other observations., Conclusions: In L1630 only a small fraction of the gas mass is traced by [Cii]. Most of the [Cii] emission in the mapped area stems from PDR surfaces. The layered edge-on structure of the molecular cloud and limitations in spatial resolution put constraints on our ability to relate different tracers to each other and to the physical conditions. From our study, we conclude that the relation between [Cii] emission and physical conditions is likely to be more complicated than often assumed. The theoretical heating efficiency is higher than the one we calculate from the observed [Cii] emission in the L1630 molecular cloud.

Published
2017
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49. Complex organic molecules in strongly UV-irradiated gas.

Author

Cuadrado S, Goicoechea JR, Cernicharo J, Fuente A, Pety J, and Tercero B

Abstract

We investigate the presence of complex organic molecules (COMs) in strongly UV-irradiated interstellar molecular gas. We have carried out a complete millimetre (mm) line survey using the IRAM 30 m telescope towards the edge of the Orion Bar photodissociation region (PDR), close to the H 2 dissociation front, a position irradiated by a very intense far-UV (FUV) radiation field. These observations have been complemented with 8.5″ resolution maps of the H 2 CO J K a , K c = 5 1,5 → 4 1,4 and C 18 O J = 3 → 2 emission at 0.9 mm. Despite being a harsh environment, we detect more than 250 lines from COMs and related precursors: H 2 CO, CH 3 OH, HCO, H 2 CCO, CH 3 CHO, H 2 CS, HCOOH, CH 3 CN, CH 2 NH, HNCO, [Formula: see text] and HC 3 N (in decreasing order of abundance). For each species, the large number of detected lines allowed us to accurately constrain their rotational temperatures ( T rot ) and column densities ( N ). Owing to subthermal excitation and intricate spectroscopy of some COMs (symmetric- and asymmetric-top molecules such as CH 3 CN and H 2 CO, respectively), a correct determination of N and T rot requires building rotational population diagrams of their rotational ladders separately. The inferred column densities are in the 10 11 - 10 13 cm -2 range. We also provide accurate upper limit abundances for chemically related molecules that might have been expected, but are not conclusively detected at the edge of the PDR (HDCO, CH 3 O, CH 3 NC, CH 3 CCH, CH 3 OCH 3 , HCOOCH 3 , CH 3 CH 2 OH, CH 3 CH 2 CN, and CH 2 CHCN). A non-thermodynamic equilibrium excitation analysis for molecules with known collisional rate coefficients suggests that some COMs arise from different PDR layers but we cannot resolve them spatially. In particular, H 2 CO and CH 3 CN survive in the extended gas directly exposed to the strong FUV flux ( T k = 150 - 250 K and T d ≳ 60 K), whereas CH 3 OH only arises from denser and cooler gas clumps in the more shielded PDR interior ( T k = 40 - 50 K). The non-detection of HDCO towards the PDR edge is consistent with the minor role of pure gas-phase deuteration at very high temperatures. We find a HCO/H 2 CO/CH 3 OH ≃ 1/5/3 abundance ratio. These ratios are different from those inferred in hot cores and shocks. Taking into account the elevated gas and dust temperatures at the edge of the Bar (mostly mantle-free grains), we suggest the following scenarios for the formation of COMs: (i) hot gas-phase reactions not included in current models; (ii) warm grain-surface chemistry; or (iii) the PDR dynamics is such that COMs or precursors formed in cold icy grains deeper inside the molecular cloud desorb and advect into the PDR.

Published
2017
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50. Spatially resolved images of reactive ions in the Orion Bar ,★★ .

Author

Goicoechea JR, Cuadrado S, Pety J, Bron E, Black JH, Cernicharo J, Chapillon E, Fuente A, and Gerin M

Abstract

We report high angular resolution (4.9″×3.0″) images of reactive ions SH + , HOC + , and SO + toward the Orion Bar photodissociation region (PDR). We used ALMA-ACA to map several rotational lines at 0.8 mm, complemented with multi-line observations obtained with the IRAM 30 m telescope. The SH + and HOC + emission is restricted to a narrow layer of 2″- to 10″-width (≈800 to 4000 AU depending on the assumed PDR geometry) that follows the vibrationally excited [Formula: see text] emission. Both ions efficiently form very close to the H/H 2 transition zone, at a depth of A v ≲1 mag into the neutral cloud, where abundant C + , S + , and [Formula: see text] coexist. SO + peaks slightly deeper into the cloud. The observed ions have low rotational temperatures ( T rot ≈10-30 K≪ T k ) and narrow line-widths (~2-3 km s -1 ), a factor of ≃2 narrower that those of the lighter reactive ion CH + . This is consistent with the higher reactivity and faster radiative pumping rates of CH + compared to the heavier ions, which are driven relatively faster toward smaller velocity dispersion by elastic collisions and toward lower T rot by inelastic collisions. We estimate column densities and average physical conditions from an excitation model ( n (H 2 )≈10 5 -10 6 cm -3 , n ( e - )≈10 cm -3 , and T k ≈200 K). Regardless of the excitation details, SH + and HOC + clearly trace the most exposed layers of the UV-irradiated molecular cloud surface, whereas SO + arises from slightly more shielded layers.

Published
2017
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