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2. Contributors

Author

Akimkin, Vitaly, primary, Babb, James, additional, Bovino, Stefano, additional, Ercolano, Barbara, additional, Gaches, Brandt, additional, Galli, Daniele, additional, Grassi, Tommaso, additional, Haugbølle, Troels, additional, Holdship, Jonathan, additional, Ioppolo, Sergio, additional, Ivlev, Alexei, additional, Kamp, Inga, additional, Le Bourlot, Jacques, additional, Lupi, Alessandro, additional, Mifsud, Duncan V., additional, Padovani, Marco, additional, Rab, Christian, additional, Ramsey, Jon, additional, Reissl, Stefan, additional, Reynolds, Daniel R., additional, Richings, Alexander J., additional, Röllig, Markus, additional, Roueff, Evelyne, additional, Ruaud, Maxime, additional, Schleicher, Dominik, additional, Shingledecker, Christopher N., additional, Silsbee, Kedron, additional, Sipilä, Olli, additional, Viti, Serena, additional, Vogt-Geisse, Stefan, additional, and Wiebe, Dmitri, additional

Published
2024
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5. PDRs4All. IX. Sulfur elemental abundance in the Orion Bar

Author

Fuente, Asunción, primary, Roueff, Evelyne, additional, Le Petit, Franck, additional, Le Bourlot, Jacques, additional, Bron, Emeric, additional, Mark Wolfire, G., additional, James Babb, F., additional, Yan, Pei-Gen, additional, Onaka, Takashi, additional, John Black, H., additional, Schroetter, Ilane, additional, Van De Putte, Dries, additional, Sidhu, Ameek, additional, Canin, Amélie, additional, Trahin, Boris, additional, Alarcón, Felipe, additional, Chown, Ryan, additional, Kannavou, Olga, additional, Berné, Olivier, additional, Habart, Emilie, additional, Peeters, Els, additional, Javier Goicoechea, R., additional, Zannese, Marion, additional, Meshaka, Raphael, additional, Okada, Yoko, additional, Röllig, Markus, additional, Le Gal, Romane, additional, Dinalva Sales, A., additional, Elisabetta Palumbo, Maria, additional, Antonio Baratta, Giuseppe, additional, Suzanne Madden, C., additional, Neelamkodan, Naslim, additional, Ziwei Zhang, E., additional, and Stancil, P.C., additional

Published
2024
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6. Bias versus variance when fitting multi-species molecular lines with a non-LTE radiative transfer model. Application to the estimation of the gas temperature and volume density

Author

Roueff, Antoine, primary, Pety, Jérôme, additional, Gerin, Maryvonne, additional, Ségal, Léontine E., additional, Goicoechea, Javier R., additional, Liszt, Harvey S., additional, Gratier, Pierre, additional, Beslic, Ivana, additional, Einig, Lucas, additional, Gaudel, Mathilde, additional, Orkisz, Jan H., additional, Palud, Pierre, additional, Santa-Maria, Miriam G., additional, de Souza Magalhaes, Victor, additional, Zakardjian, Antoine, additional, Bardeau, Sébastien, additional, Bron, Emeric, additional, Chainais, Pierre, additional, Coudé, Simon, additional, Demyk, Karine, additional, Guzman, Viviana V., additional, Hughes, Annie, additional, Languignon, David, additional, Levrier, François, additional, Lis, Dariusz C., additional, Le Bourlot, Jacques, additional, Le Petit, Franck, additional, Peretto, Nicolas, additional, Roueff, Evelyne, additional, Sievers, Albrecht, additional, and Thouvenin, Pierre-Antoine, additional

Published
2024
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7. Neural network-based emulation of interstellar medium models

Author

Centre National de la Recherche Scientifique (France), Agence Nationale de la Recherche (France), Ministerio de Ciencia e Innovación (España), NASA Jet Propulsion Laboratory, Universities Space Research Association (US), Palud, Pierre [0000-0002-5850-6325], Einig, Lucas [0000-0003-4250-7638], Le Petit, Franck [0000-0001-8738-6724], Bron, Emeric [0000-0003-1532-7818], #NODATA#, Chanussot, Jocelyn [0000-0003-4817-2875], Pety, Jérôme [0000-0003-3061-6546], Thouvenin, Pierre-Antoine [0000-0003-1246-9458], Bešlić, Ivana [0000-0003-0583-7363], Santa-María, Miriam G. [0000-0002-3941-0360], Orkisz, Jan H. [0000-0002-3382-9208], Ségal, Léontine E. [0009-0002-3993-5754], Zakardjian, Antoine [0000-0002-4240-6012], Gerin, Maryvonne [0000-0002-2418-7952], Goicoechea, Javier R. [0000-0001-7046-4319], Gratier, Pierre [0000-0002-6636-4304], Levrier, François [0000-0002-3065-9944], Liszt, Harvey S. [0000-0002-6116-1911], Le Bourlot, Jacques [0000-0003-3920-8063], Roueff, Antoine [0000-0002-7498-4407], Sievers, Albrecht [0000-0003-0151-2924], Palud, Pierre, Einig, Lucas, Le Petit, Franck, Bron, Emeric, Chainais, Pierre, Chanussot, Jocelyn, Pety, Jérôme, Thouvenin, Pierre-Antoine, Languignon, David, Bešlić, Ivana, Santa-María, Miriam G., Orkisz, Jan H., Ségal, Léontine E., Zakardjian, Antoine, Bardeau, Sébastien, Gerin, Maryvonne, Goicoechea, Javier R., Gratier, Pierre, Guzman, Viviana V., Hughes, Annie, Levrier, François, Liszt, Harvey S., Le Bourlot, Jacques, Roueff, Antoine, Sievers, Albrecht, Centre National de la Recherche Scientifique (France), Agence Nationale de la Recherche (France), Ministerio de Ciencia e Innovación (España), NASA Jet Propulsion Laboratory, Universities Space Research Association (US), Palud, Pierre [0000-0002-5850-6325], Einig, Lucas [0000-0003-4250-7638], Le Petit, Franck [0000-0001-8738-6724], Bron, Emeric [0000-0003-1532-7818], #NODATA#, Chanussot, Jocelyn [0000-0003-4817-2875], Pety, Jérôme [0000-0003-3061-6546], Thouvenin, Pierre-Antoine [0000-0003-1246-9458], Bešlić, Ivana [0000-0003-0583-7363], Santa-María, Miriam G. [0000-0002-3941-0360], Orkisz, Jan H. [0000-0002-3382-9208], Ségal, Léontine E. [0009-0002-3993-5754], Zakardjian, Antoine [0000-0002-4240-6012], Gerin, Maryvonne [0000-0002-2418-7952], Goicoechea, Javier R. [0000-0001-7046-4319], Gratier, Pierre [0000-0002-6636-4304], Levrier, François [0000-0002-3065-9944], Liszt, Harvey S. [0000-0002-6116-1911], Le Bourlot, Jacques [0000-0003-3920-8063], Roueff, Antoine [0000-0002-7498-4407], Sievers, Albrecht [0000-0003-0151-2924], Palud, Pierre, Einig, Lucas, Le Petit, Franck, Bron, Emeric, Chainais, Pierre, Chanussot, Jocelyn, Pety, Jérôme, Thouvenin, Pierre-Antoine, Languignon, David, Bešlić, Ivana, Santa-María, Miriam G., Orkisz, Jan H., Ségal, Léontine E., Zakardjian, Antoine, Bardeau, Sébastien, Gerin, Maryvonne, Goicoechea, Javier R., Gratier, Pierre, Guzman, Viviana V., Hughes, Annie, Levrier, François, Liszt, Harvey S., Le Bourlot, Jacques, Roueff, Antoine, and Sievers, Albrecht

Abstract

The interpretation of observations of atomic and molecular tracers in the galactic and extragalactic interstellar medium (ISM) requires comparisons with state-of-the-art astrophysical models to infer some physical conditions. Usually, ISM models are too time-consuming for such inference procedures, as they call for numerous model evaluations. As a result, they are often replaced by an interpolation of a grid of precomputed models. We propose a new general method to derive faster, lighter, and more accurate approximations of the model from a grid of precomputed models. These emulators are defined with artificial neural networks (ANNs) designed and trained to address the specificities inherent in ISM models. Indeed, such models often predict many observables (e.g., line intensities) from just a few input physical parameters and can yield outliers due to numerical instabilities or physical bistabilities. We propose applying five strategies to address these characteristics: 1) an outlier removal procedure; 2) a clustering method that yields homogeneous subsets of lines that are simpler to predict with different ANNs; 3) a dimension reduction technique that enables to adequately size the network architecture; 4) the physical inputs are augmented with a polynomial transform to ease the learning of nonlinearities; and 5) a dense architecture to ease the learning of simple relations. We compare the proposed ANNs with standard classes of interpolation methods to emulate the Meudon PDR code, a representative ISM numerical model. Combinations of the proposed strategies outperform all interpolation methods by a factor of 2 on the average error, reaching 4.5% on the Meudon PDR code. These networks are also 1000 times faster than accurate interpolation methods and require ten to forty times less memory. This work will enable efficient inferences on wide-field multiline observations of the ISM.

Published
2023

8. Deep learning denoising by dimension reduction: Application to the ORION-B line cubes

Author

Centre National de la Recherche Scientifique (France), Agence Nationale de la Recherche (France), Centre National D'Etudes Spatiales (France), Ministerio de Ciencia e Innovación (España), National Aeronautics and Space Administration (US), Universities Space Research Association (US), Einig, Lucas [0000-0003-4250-7638], Pety, Jérôme [0000-0003-3061-6546], #NODATA#, Chanussot, Jocelyn [0000-0003-4817-2875], Gerin, Maryvonne [0000-0002-2418-7952], Orkisz, Jan H. [0000-0002-3382-9208], Palud, Pierre [0000-0002-5850-6325], Santa-María, Miriam G. [0000-0002-3941-0360], Bešlić, Ivana [0000-0003-0583-7363], Bron, Emeric E. [0000-0003-1532-7818], Chainais,Pierre [0000-0003-4377-7584], Goicoechea, Javier R. [0000-0001-7046-4319], Gratier, Pierre [0000-0002-6636-4304], Lis, Dariuscz C. [0000-0002-0500-4700], Le Bourlot,Jacques [0000-0003-3920-8063], Le Petit, Franck [0000-0001-8738-6724], Roueff, Evelyne [0000-0002-4949-8562], Sievers, Albrecht [0000-0003-0151-2924], Thouvenin, Pierre-Antoine [0000-0003-1246-9458], Einig, Lucas, Pety, Jérôme, Roueff, Antoine, Vandame, Paul, Chanussot, Jocelyn, Gerin, Maryvonne, Orkisz, Jan H., Palud, Pierre, Santa-María, Miriam G., Souza Magalhaes, Victor de, Bešlić, Ivana, Bardeau, Sébastien, Bron, Emeric E., Chainais,Pierre, Goicoechea, Javier R., Gratier, Pierre, Guzman Veloso, Viviana, Hughes, Annie, Kainulainen, Jouni, Languignon, David, Lallement, Rosine, Levrier, François, Lis, Dariuscz C., Liszt, Harvey, Le Bourlot,Jacques, Le Petit, Franck, Öberg,Karin Danielsson, Peretto, Nicolas, Roueff, Evelyne, Sievers, Albrecht, Thouvenin, Pierre-Antoine, Tremblin, Pascal, Centre National de la Recherche Scientifique (France), Agence Nationale de la Recherche (France), Centre National D'Etudes Spatiales (France), Ministerio de Ciencia e Innovación (España), National Aeronautics and Space Administration (US), Universities Space Research Association (US), Einig, Lucas [0000-0003-4250-7638], Pety, Jérôme [0000-0003-3061-6546], #NODATA#, Chanussot, Jocelyn [0000-0003-4817-2875], Gerin, Maryvonne [0000-0002-2418-7952], Orkisz, Jan H. [0000-0002-3382-9208], Palud, Pierre [0000-0002-5850-6325], Santa-María, Miriam G. [0000-0002-3941-0360], Bešlić, Ivana [0000-0003-0583-7363], Bron, Emeric E. [0000-0003-1532-7818], Chainais,Pierre [0000-0003-4377-7584], Goicoechea, Javier R. [0000-0001-7046-4319], Gratier, Pierre [0000-0002-6636-4304], Lis, Dariuscz C. [0000-0002-0500-4700], Le Bourlot,Jacques [0000-0003-3920-8063], Le Petit, Franck [0000-0001-8738-6724], Roueff, Evelyne [0000-0002-4949-8562], Sievers, Albrecht [0000-0003-0151-2924], Thouvenin, Pierre-Antoine [0000-0003-1246-9458], Einig, Lucas, Pety, Jérôme, Roueff, Antoine, Vandame, Paul, Chanussot, Jocelyn, Gerin, Maryvonne, Orkisz, Jan H., Palud, Pierre, Santa-María, Miriam G., Souza Magalhaes, Victor de, Bešlić, Ivana, Bardeau, Sébastien, Bron, Emeric E., Chainais,Pierre, Goicoechea, Javier R., Gratier, Pierre, Guzman Veloso, Viviana, Hughes, Annie, Kainulainen, Jouni, Languignon, David, Lallement, Rosine, Levrier, François, Lis, Dariuscz C., Liszt, Harvey, Le Bourlot,Jacques, Le Petit, Franck, Öberg,Karin Danielsson, Peretto, Nicolas, Roueff, Evelyne, Sievers, Albrecht, Thouvenin, Pierre-Antoine, and Tremblin, Pascal

Abstract

Context. The availability of large bandwidth receivers for millimeter radio telescopes allows the acquisition of position-position-frequency data cubes over a wide field of view and a broad frequency coverage. These cubes contain much information on the physical, chemical, and kinematical properties of the emitting gas. However, their large size coupled with inhomogenous signal-to-noise ratio (SNR) are major challenges for consistent analysis and interpretation.Aims. We search for a denoising method of the low SNR regions of the studied data cubes that would allow to recover the low SNR emission without distorting the signals with high SNR.Methods. We perform an in-depth data analysis of the 13 CO and C 17 O (1 -- 0) data cubes obtained as part of the ORION-B large program performed at the IRAM 30m telescope. We analyse the statistical properties of the noise and the evolution of the correlation of the signal in a given frequency channel with that of the adjacent channels. This allows us to propose significant improvements of typical autoassociative neural networks, often used to denoise hyperspectral Earth remote sensing data. Applying this method to the 13 CO (1 -- 0) cube, we compare the denoised data with those derived with the multiple Gaussian fitting algorithm ROHSA, considered as the state of the art procedure for data line cubes.Results. The nature of astronomical spectral data cubes is distinct from that of the hyperspectral data usually studied in the Earth remote sensing literature because the observed intensities become statistically independent beyond a short channel separation. This lack of redundancy in data has led us to adapt the method, notably by taking into account the sparsity of the signal along the spectral axis. The application of the proposed algorithm leads to an increase of the SNR in voxels with weak signal, while preserving the spectral shape of the data in high SNR voxels.Conclusions. The proposed algorithm that combines a detailed ana

Published
2023

9. Neural network-based emulation of interstellar medium models

Author

Palud, Pierre, primary, Einig, Lucas, additional, Le Petit, Franck, additional, Bron, Émeric, additional, Chainais, Pierre, additional, Chanussot, Jocelyn, additional, Pety, Jérôme, additional, Thouvenin, Pierre-Antoine, additional, Languignon, David, additional, Bešlić, Ivana, additional, Santa-Maria, Miriam G., additional, Orkisz, Jan H., additional, Ségal, Léontine E., additional, Zakardjian, Antoine, additional, Bardeau, Sébastien, additional, Gerin, Maryvonne, additional, Goicoechea, Javier R., additional, Gratier, Pierre, additional, Guzman, Viviana V., additional, Hughes, Annie, additional, Levrier, François, additional, Liszt, Harvey S., additional, Le Bourlot, Jacques, additional, Roueff, Antoine, additional, and Sievers, Albrecht, additional

Published
2023
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10. Deep learning denoising by dimension reduction: Application to the ORION-B line cubes

Author

Einig, Lucas, primary, Pety, Jérôme, additional, Roueff, Antoine, additional, Vandame, Paul, additional, Chanussot, Jocelyn, additional, Gerin, Maryvonne, additional, Orkisz, Jan H., additional, Palud, Pierre, additional, Santa-Maria, Miriam G., additional, de Souza Magalhaes, Victor, additional, Bešlić, Ivana, additional, Bardeau, Sébastien, additional, Bron, Emeric, additional, Chainais, Pierre, additional, Goicoechea, Javier R., additional, Gratier, Pierre, additional, Guzmán, Viviana V., additional, Hughes, Annie, additional, Kainulainen, Jouni, additional, Languignon, David, additional, Lallement, Rosine, additional, Levrier, François, additional, Lis, Dariusz C., additional, Liszt, Harvey S., additional, Le Bourlot, Jacques, additional, Le Petit, Franck, additional, Öberg, Karin, additional, Peretto, Nicolas, additional, Roueff, Evelyne, additional, Sievers, Albrecht, additional, Thouvenin, Pierre-Antoine, additional, and Tremblin, Pascal, additional

Published
2023
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11. Revealing which Combinations of Molecular Lines are Sensitive to the Gas Physical Parameters of Molecular Clouds

Author

Pety Jérôme, Gerin Maryvonne, Bron Emeric, Gratier Pierre, Orkisz Jan H., Palud Pierre, Roueff Antoine, Einig Lucas, Santa-Maria Miriam G., de Souza Magalhaes Victor, Bardeau Sébastien, Chanussot Jocelyn, Chainais Pierre, Goicoechea Javier R., Guzman Viviana V., Hughes Annie, Kainulainen Jouni, Languignon David, Levrier François, Lis Darek, Liszt Harvey S., Le Bourlot Jacques, Le Petit Franck, Oberg Karin, Peretto Nicolas, Roueff Evelyne, Sievers Albrecht, Thouvenin Pierre-Antoine, and Tremblin Pascal

Subjects
Physics, QC1-999
Abstract

Atoms and molecules have long been thought to be versatile tracers of the cold neutral gas in the universe, from high-redshift galaxies to star forming regions and proto-planetary disks, because their internal degrees of freedom bear the signature of the physical conditions where these species reside. However, the promise that molecular emission has a strong diagnostic power of the underlying physical and chemical state is still hampered by the difficulty to combine sophisticated chemical codes with gas dynamics. It is therefore important 1) to acquire self-consistent data sets that can be used as templates for this theoretical work, and 2) to reveal the diagnostic capabilities of molecular lines accurately. The advent of sensitive wideband spectrometers in the (sub)- millimeter domain (e.g., IRAM-30m/EMIR, NOEMA, …) during the 2010s has allowed us to image a significant fraction of a Giant Molecular Cloud with enough sensitivity to detect tens of molecular lines in the 70 – 116 GHz frequency range. Machine learning techniques applied to these data start to deliver the next generation of molecular line diagnostics of mass, density, temperature, and radiation field.

Published
2022
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12. Learning from model grids: Tracers of the ionization fraction in the ISM

Author

Bron Emeric, Roueff Evelyne, Gerin Maryvonne, Pety Jérôme, Gratier Pierre, Le Petit Franck, Guzman Viviana, Orkisz Jan, de Souza Magalhaes Victor, Gaudel Mathilde, Palud Pierre, Einig Lucas, Bardeau Sébastien, Chainais Pierre, Chanussot Jocelyn, Goicoechea Javier, Hughes Annie, Kainulainen Jouni, Languignon David, Le Bourlot Jacques, Levrier François, Lis Darek, Liszt Harvey, Öberg Karin, Peretto Nicolas, Roueff Antoine, Sievers Albrecht, Thouvenin Pierre-Antoine, and Tremblin Pascal

Subjects
Physics, QC1-999
Abstract

The ionization fraction in neutral interstellar clouds is a key physical parameter controlling multiple physical and chemical processes, and varying by orders of magnitude from the UV irradiated surface of the cloud to its cosmic-ray dominated central regions. Traditional observational tracers of the ionization fraction, which mostly rely on deuteration ratios of molecules like HCO+, suffer from the fact that the deuterated molecules are only detected in a tiny fraction of a given Giant Molecular Cloud (GMC). In [1], we propose a machine learning-based, semi-automatic method to search in a large dataset of astrochemical model results for new tracers of the ionization fraction, and propose several new tracers relevant in different ranges of physical conditions.

Published
2022
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15. Gas kinematics around filamentary structures in the Orion B cloud

Author

Agence Nationale de la Recherche (France), Centre National de la Recherche Scientifique (France), Centre National D'Etudes Spatiales (France), l'Observatoire de Paris, Ministerio de Ciencia, Innovación y Universidades (España), Swedish Research Council, Orkisz, Jan H. [0000-0002-3382-9208], Pety, Jérôme [0000-0003-3061-6546], Roueff, Antoine [0000-0002-7498-4407], Marchal, Antoine [0000-0002-5501-232X], Levrier, François [0000-0002-3065-9944], Miville-Deschênes, Marc-Antoine [0000-0002-7351-6062], Goicoechea, Javier R. [0000-0001-7046-4319], Roueff, Evelyne [0000-0002-4949-8562], Santa-Maria, Miriam G. [0000-0002-3941-0360], Bron, Emeric [0000-0003-1532-7818], Chainais, Pierre [0000-0003-4377-7584], Chanussot, Jocelyn [0000-0003-4817-2875], Gratier, Pierre [0000-0002-6636-4304], Guzman, Viviana [0000-0003-4784-3040], Le Bourlot,Jacques [0000-0003-3920-8063], Liszt, Harvey [0000-0002-6116-1911], Gaudel, Mathilde, Orkisz, Jan H., Gerin, Maryvonne, Pety, Jérôme, Roueff, Antoine, Marchal, Antoine, Levrier, François, Miville-Deschênes, Marc-Antoine, Goicoechea, Javier R., Roueff, Evelyne, Le Petit, Franck, Souza Magalhaes, Victor de, Palud, Pierre, Santa-Maria, Miriam G., Vono, Maxime, Bardeau, Sébastien, Bron, Emeric, Chainais, Pierre, Chanussot, Jocelyn, Gratier, Pierre, Guzman, Viviana, Hughes, Annie, Kainulainen, Jouni, Languignon, David, Le Bourlot,Jacques, Liszt, Harvey, Öberg, Karin, Peretto, Nicolas, Sievers, Albrecht, Tremblin, Pascal, Agence Nationale de la Recherche (France), Centre National de la Recherche Scientifique (France), Centre National D'Etudes Spatiales (France), l'Observatoire de Paris, Ministerio de Ciencia, Innovación y Universidades (España), Swedish Research Council, Orkisz, Jan H. [0000-0002-3382-9208], Pety, Jérôme [0000-0003-3061-6546], Roueff, Antoine [0000-0002-7498-4407], Marchal, Antoine [0000-0002-5501-232X], Levrier, François [0000-0002-3065-9944], Miville-Deschênes, Marc-Antoine [0000-0002-7351-6062], Goicoechea, Javier R. [0000-0001-7046-4319], Roueff, Evelyne [0000-0002-4949-8562], Santa-Maria, Miriam G. [0000-0002-3941-0360], Bron, Emeric [0000-0003-1532-7818], Chainais, Pierre [0000-0003-4377-7584], Chanussot, Jocelyn [0000-0003-4817-2875], Gratier, Pierre [0000-0002-6636-4304], Guzman, Viviana [0000-0003-4784-3040], Le Bourlot,Jacques [0000-0003-3920-8063], Liszt, Harvey [0000-0002-6116-1911], Gaudel, Mathilde, Orkisz, Jan H., Gerin, Maryvonne, Pety, Jérôme, Roueff, Antoine, Marchal, Antoine, Levrier, François, Miville-Deschênes, Marc-Antoine, Goicoechea, Javier R., Roueff, Evelyne, Le Petit, Franck, Souza Magalhaes, Victor de, Palud, Pierre, Santa-Maria, Miriam G., Vono, Maxime, Bardeau, Sébastien, Bron, Emeric, Chainais, Pierre, Chanussot, Jocelyn, Gratier, Pierre, Guzman, Viviana, Hughes, Annie, Kainulainen, Jouni, Languignon, David, Le Bourlot,Jacques, Liszt, Harvey, Öberg, Karin, Peretto, Nicolas, Sievers, Albrecht, and Tremblin, Pascal

Abstract

Understanding the initial properties of star-forming material and how they affect the star formation process is key. From an observational point of view, the feedback from young high-mass stars on future star formation properties is still poorly constrained. In the framework of the IRAM 30m ORION-B large program, we obtained observations of the translucent and moderately dense gas, which we used to analyze the kinematics over a field of 5 deg^2 around the filamentary structures. We used the ROHSA algorithm to decompose and de-noise the C18O(1-0) and 13CO(1-0) signals by taking the spatial coherence of the emission into account. We produced gas column density and mean velocity maps to estimate the relative orientation of their spatial gradients. We identified three cloud velocity layers at different systemic velocities and extracted the filaments in each velocity layer. The filaments are preferentially located in regions of low centroid velocity gradients. By comparing the relative orientation between the column density and velocity gradients of each layer from the ORION-B observations and synthetic observations from 3D kinematic toy models, we distinguish two types of behavior in the dynamics around filaments: (i) radial flows perpendicular to the filament axis that can be either inflows (increasing the filament mass) or outflows and (ii) longitudinal flows along the filament axis. The former case is seen in the Orion B data, while the latter is not identified. We have also identified asymmetrical flow patterns, usually associated with filaments located at the edge of an HII region. This is the first observational study to highlight feedback from HII regions on filament formation and, thus, on star formation in the Orion B cloud. This simple statistical method can be used for any molecular cloud to obtain coherent information on the kinematics.

Published
2022

16. Understanding the temperatures of H3+ and H2 in diffuse interstellar sightlines.

Author

Le Bourlot, Jacques, Roueff, Evelyne, Le Petit, Franck, Kehrein, Florian, Oetjens, Annika, and Kreckel, Holger

Subjects
*INTERSTELLAR medium, *RADIATIVE transitions, *TEMPERATURE, *LOW temperatures, *MOLECULAR clouds
Abstract

The triatomic hydrogen ion $ \mathrm {H}_3^+ $ H 3 + is one of the most important species for the gas phase chemistry of the interstellar medium. Observations of $ \mathrm {H}_3^+ $ H 3 + are used to constrain important physical and chemical parameters of interstellar environments. However, the temperatures inferred from the two lowest rotational states of $ \mathrm {H}_3^+ $ H 3 + in diffuse lines of sight – typically the only ones observable – appear consistently lower than the temperatures derived from H $ _2 $ 2 observations in the same sightlines. All previous attempts at modelling the temperatures of $ \mathrm {H}_3^+ $ H 3 + in the diffuse interstellar medium failed to reproduce the observational results. Here we present new studies, comparing an independent master equation for H $ _3^+ $ 3 + level populations to results from the Meudon PDR code for photon dominated regions. We show that the populations of the lowest rotational states of $ \mathrm {H}_3^+ $ H 3 + are strongly affected by the formation reaction and that H $ _3^+ $ 3 + ions experience incomplete thermalisation before their destruction by free electrons. Furthermore, we find that for quantitative analysis more than two levels of H $ _3^+ $ 3 + have to be considered and that it is crucial to include radiative transitions as well as collisions with H2. Our models of typical diffuse interstellar sightlines show very good agreement with observational data, and thus they may finally resolve the perceived temperature difference attributed to these two fundamental species. [ABSTRACT FROM AUTHOR]

Published
2024
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18. Gas kinematics around filamentary structures in the Orion B cloud

Author

Gaudel, Mathilde, primary, Orkisz, Jan H., additional, Gerin, Maryvonne, additional, Pety, Jérôme, additional, Roueff, Antoine, additional, Marchal, Antoine, additional, Levrier, François, additional, Miville-Deschênes, Marc-Antoine, additional, Goicoechea, Javier R., additional, Roueff, Evelyne, additional, Le Petit, Franck, additional, de Souza Magalhaes, Victor, additional, Palud, Pierre, additional, Santa-Maria, Miriam G., additional, Vono, Maxime, additional, Bardeau, Sébastien, additional, Bron, Emeric, additional, Chainais, Pierre, additional, Chanussot, Jocelyn, additional, Gratier, Pierre, additional, Guzman, Viviana, additional, Hughes, Annie, additional, Kainulainen, Jouni, additional, Languignon, David, additional, Le Bourlot, Jacques, additional, Liszt, Harvey, additional, Öberg, Karin, additional, Peretto, Nicolas, additional, Sievers, Albrecht, additional, and Tremblin, Pascal, additional

Published
2023
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19. Tracers of the ionization fraction in dense and translucent gas

Author

Bron, Emeric, primary, Roueff, Evelyne, additional, Gerin, Maryvonne, additional, Pety, Jérôme, additional, Gratier, Pierre, additional, Le Petit, Franck, additional, Guzman, Viviana, additional, Orkisz, Jan H., additional, de Souza Magalhaes, Victor, additional, Gaudel, Mathilde, additional, Vono, Maxime, additional, Bardeau, Sébastien, additional, Chainais, Pierre, additional, Goicoechea, Javier R., additional, Hughes, Annie, additional, Kainulainen, Jouni, additional, Languignon, David, additional, Le Bourlot, Jacques, additional, Levrier, François, additional, Liszt, Harvey, additional, Öberg, Karin, additional, Peretto, Nicolas, additional, Roueff, Antoine, additional, and Sievers, Albrecht, additional

Published
2020
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20. Quantitative inference of the H2 column densities from 3 mm molecular emission: case study towards Orion B

Author

Gratier, Pierre, primary, Pety, Jérôme, additional, Bron, Emeric, additional, Roueff, Antoine, additional, Orkisz, Jan H., additional, Gerin, Maryvonne, additional, de Souza Magalhaes, Victor, additional, Gaudel, Mathilde, additional, Vono, Maxime, additional, Bardeau, Sébastien, additional, Chanussot, Jocelyn, additional, Chainais, Pierre, additional, Goicoechea, Javier R., additional, Guzmán, Viviana V., additional, Hughes, Annie, additional, Kainulainen, Jouni, additional, Languignon, David, additional, Le Bourlot, Jacques, additional, Le Petit, Franck, additional, Levrier, François, additional, Liszt, Harvey, additional, Peretto, Nicolas, additional, Roueff, Evelyne, additional, and Sievers, Albrecht, additional

Published
2020
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21. C18O,13CO, and12CO abundances and excitation temperatures in the Orion B molecular cloud

Author

Roueff, Antoine, primary, Gerin, Maryvonne, additional, Gratier, Pierre, additional, Levrier, François, additional, Pety, Jérôme, additional, Gaudel, Mathilde, additional, Goicoechea, Javier R., additional, Orkisz, Jan H., additional, de Souza Magalhaes, Victor, additional, Vono, Maxime, additional, Bardeau, Sébastien, additional, Bron, Emeric, additional, Chanussot, Jocelyn, additional, Chainais, Pierre, additional, Guzman, Viviana V., additional, Hughes, Annie, additional, Kainulainen, Jouni, additional, Languignon, David, additional, Le Bourlot, Jacques, additional, Le Petit, Franck, additional, Liszt, Harvey S., additional, Marchal, Antoine, additional, Miville-Deschênes, Marc-Antoine, additional, Peretto, Nicolas, additional, Roueff, Evelyne, additional, and Sievers, Albrecht, additional

Published
2020
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23. Tracers of the ionization fraction in dense and translucent gas: I. Automated exploitation of massive astrochemical model grids

Author

Centre National de la Recherche Scientifique (France), Centre National D'Etudes Spatiales (France), Ministerio de Ciencia, Innovación y Universidades (España), Bron, Emeric, Roueff, Evelyne, Gerin, Maryvonne, Pety, Jérôme, Gratier, Pierre, Petit, F. le, Guzmán, Viviana, Orkisz, Jan H., Souza Magalhaes, Victor de, Gaudel, Mathilde, Vono, Maxime, Bardeau, Sébastien, Chainais, Pierre, Goicoechea, Javier R., Hughes, Annie, Kainulainen, Jouni, Languignon, David, Le Bourlot, Jacques, Levrier, François, Liszt, Harvey, Öberg, Karin, Peretto, Nicolas, Roueff, Antoine, Sievers, Albrecht, Centre National de la Recherche Scientifique (France), Centre National D'Etudes Spatiales (France), Ministerio de Ciencia, Innovación y Universidades (España), Bron, Emeric, Roueff, Evelyne, Gerin, Maryvonne, Pety, Jérôme, Gratier, Pierre, Petit, F. le, Guzmán, Viviana, Orkisz, Jan H., Souza Magalhaes, Victor de, Gaudel, Mathilde, Vono, Maxime, Bardeau, Sébastien, Chainais, Pierre, Goicoechea, Javier R., Hughes, Annie, Kainulainen, Jouni, Languignon, David, Le Bourlot, Jacques, Levrier, François, Liszt, Harvey, Öberg, Karin, Peretto, Nicolas, Roueff, Antoine, and Sievers, Albrecht

Abstract

Context. The ionization fraction in the neutral interstellar medium (ISM) plays a key role in the physics and chemistry of the ISM, from controlling the coupling of the gas to the magnetic field to allowing fast ion-neutral reactions that drive interstellar chemistry. Most estimations of the ionization fraction have relied on deuterated species such as DCO+, whose detection is limited to dense cores representing an extremely small fraction of the volume of the giant molecular clouds that they are part of. As large field-of-view hyperspectral maps become available, new tracers may be found. The growth of observational datasets is paralleled by the growth of massive modeling datasets and new methods need to be devised to exploit the wealth of information they contain. Aims. We search for the best observable tracers of the ionization fraction based on a grid of astrochemical models, with the broader aim of finding a general automated method applicable to searching for tracers of any unobservable quantity based on grids of models. Methods. We built grids of models that randomly sample a large range of physical conditions (unobservable quantities such as gas density, temperature, elemental abundances, etc.) and computed the corresponding observables (line intensities, column densities) and the ionization fraction. We estimated the predictive power of each potential tracer by training a random forest model to predict the ionization fraction from that tracer, based on these model grids. Results. In both translucent medium and cold dense medium conditions, we found several observable tracers with very good predictive power for the ionization fraction. Many tracers in cold dense medium conditions are found to be better and more widely applicable than the traditional DCO+/HCO+ ratio. We also provide simpler analytical fits for estimating the ionization fraction from the best tracers, and for estimating the associated uncertainties. We discuss the limitations of the present st

Published
2020

24. Quantitative inference of the H2 column densities from 3 mm molecular emission: case study towards Orion B

Author

Centre National de la Recherche Scientifique (France), Max Planck Society, Instituto Geográfico Nacional (España), Université Paris-Saclay, Istituto Nazionale di Astrofisica, Ministerio de Ciencia, Innovación y Universidades (España), Gratier, Pierre, Pety, Jérôme, Bron, Emeric, Roueff, Antoine, Orkisz, Jan H., Gerin, Maryvonne, Souza Magalhaes, Victor de, Gaudel, Mathilde, Vono, Maxime, Bardeau, Sébastien, Chanussot, Jocelyn, Chainais, Pierre, Goicoechea, Javier R., Guzmán, Viviana V., Hughes, Annie, Kainulainen, Jouni, Languignon, David, Le Bourlot, Jacques, Le Petit, Franck, Levrier, François, Liszt, Harvey, Peretto, Nicolas, Roueff, Evelyne, Sievers, Albrecht, Centre National de la Recherche Scientifique (France), Max Planck Society, Instituto Geográfico Nacional (España), Université Paris-Saclay, Istituto Nazionale di Astrofisica, Ministerio de Ciencia, Innovación y Universidades (España), Gratier, Pierre, Pety, Jérôme, Bron, Emeric, Roueff, Antoine, Orkisz, Jan H., Gerin, Maryvonne, Souza Magalhaes, Victor de, Gaudel, Mathilde, Vono, Maxime, Bardeau, Sébastien, Chanussot, Jocelyn, Chainais, Pierre, Goicoechea, Javier R., Guzmán, Viviana V., Hughes, Annie, Kainulainen, Jouni, Languignon, David, Le Bourlot, Jacques, Le Petit, Franck, Levrier, François, Liszt, Harvey, Peretto, Nicolas, Roueff, Evelyne, and Sievers, Albrecht

Abstract

Molecular hydrogen being unobservable in cold molecular clouds, the column density measurements of molecular gas currently rely either on dust emission observation in the far-IR or on star counting. (Sub-)millimeter observations of numerous trace molecules are effective from ground based telescopes, but the relationships between the emission of one molecular line and the H2 column density (NH2) is non-linear and sensitive to excitation conditions, optical depths, abundance variations due to the underlying physico-chemistry. We aim to use multi-molecule line emission to infer NH2 from radio observations. We propose a data-driven approach to determine NH2 from radio molecular line observations. We use supervised machine learning methods (Random Forests) on wide-field hyperspectral IRAM-30m observations of the Orion B molecular cloud to train a predictor of NH2, using a limited set of molecular lines as input, and the Herschel-based dust-derived NH2 as ground truth output. For conditions similar to the Orion B molecular cloud, we obtain predictions of NH2 within a typical factor of 1.2 from the Herschel-based estimates. An analysis of the contributions of the different lines to the predictions show that the most important lines are $^{13}$CO(1-0), $^{12}$CO(1-0), C$^{18}$O(1-0), and HCO$^+$(1-0). A detailed analysis distinguishing between diffuse, translucent, filamentary, and dense core conditions show that the importance of these four lines depends on the regime, and that it is recommended to add the N$_2$H$^+$(1-0) and CH$_3$OH(20-10) lines for the prediction of NH2 in dense core conditions. This article opens a promising avenue to directly infer important physical parameters from the molecular line emission in the millimeter domain. The next step will be to try to infer several parameters simultaneously (e.g., NH2 and far-UV illumination field) to further test the method. [Abridged]

Published
2020

26. Origin of CH+ in diffuse molecular clouds: Warm H2 and ion-neutral drift

Author

Valdivia, Valeska, Godard, Benjamin, Hennebelle, Patrick, Gerin, Maryvonne, Lesaffre, Pierre, Le Bourlot, Jacques, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'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), Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Laboratoire de Radioastronomie (LRA), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-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)-Université Paris Diderot - Paris 7 (UPD7)-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), 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), Ctr Astrobiol CSIC INTA, Lab Astofis Mol, Madrid 28850, Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), 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 Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), and 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)

Subjects
[PHYS]Physics [physics], astrochemistry, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], magnetohydrodynamics (MHD), ISM: clouds, ComputingMilieux_MISCELLANEOUS, ISM: molecules, ISM: general, methods: numerical
Abstract

International audience; Context. Molecular clouds are known to be magnetised and to display a turbulent and complex structure where warm and cold phases are interwoven. The turbulent motions within molecular clouds transport molecules, and the presence of magnetic fields induces a relative velocity between neutrals and ions known as the ion-neutral drift (vd). These effects all together can influence the chemical evolution of the clouds.Aims. This paper assesses the roles of two physical phenomena which have previously been invoked to boost the production of CH+ under realistic physical conditions: the presence of warm H2 and the increased formation rate due to the ion-neutral drift.MMethods. We performed ideal magnetohydrodynamical (MHD) simulations that include the heating and cooling of the multiphase interstellar medium (ISM), and where we treat dynamically the formation of the H2 molecule. In a post-processing step we compute the abundances of species at chemical equilibrium using a solver that we developed. The solver uses the physical conditions of the gas as input parameters, and can also prescribe the H2 fraction if needed. We validate our approach by showing that the H2 molecule generally has a much longer chemical evolution timescale compared to the other species.Results. We show that CH+ is efficiently formed at the edge of clumps, in regions where the H2 fraction is low (0.3−30%) but nevertheless higher than its equilibrium value, and where the gas temperature is high (≳ 300 K). We show that warm and out of equilibrium H2 increases the integrated column densities of CH+ by one order of magnitude up to values still ~ 3−10 times lower than those observed in the diffuse ISM. We balance the Lorentz force with the ion-neutral drag to estimate the ion-drift velocities from our ideal MHD simulations. We find that the ion-neutral drift velocity distribution peaks around ~ 0.04 km s-1, and that high drift velocities are too rare to have a significant statistical impact on the abundances of CH+. Compared to previous works, our multiphase simulations reduce the spread in vd, and our self-consistent treatment of the ionisation leads to much reduced vd. Nevertheless, our resolution study shows that this velocity distribution is not converged: the ion-neutral drift has a higher impact on CH+ at higher resolution. On the other hand, our ideal MHD simulations do not include ambipolar diffusion, which would yield lower drift velocities.Conclusions. Within these limitations, we conclude that warm H2 is a key ingredient in the efficient formation of CH+ and that the ambipolar diffusion has very little influence on the abundance of CH+, mainly due to the small drift velocities obtained. However, we point out that small-scale processes and other non-thermal processes not included in our MHD simulation may be of crucial importance, and higher resolution studies with better controlled dissipation processes are needed.

Published
2017
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28. Surface chemistry in the interstellar medium

Author

Bron, Emeric, Le Bourlot, Jacques, Le Petit, Franck, 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), and École normale supérieure - Paris (ENS Paris)

Subjects
[PHYS]Physics [physics], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2014
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30. Molecular line tracers of high-mass star forming regions

Author

Nagy, Zsofia, Van der Tak, Floris, Ossenkopf, Volker, Bergin, Edwin, Black, John, Faure, Alexandre, Fuller, Gary, Gerin, Maryvonne, Goicoechea, Javier, Joblin, Christine, Le Bourlot, Jacques, Le Petit, Franck, Makai, Zoltan, Plume, Rene, Roellig, Markus, Spaans, Marco, Tolls, Volker, Kapteyn Astronomical Institute, and Astronomy

Abstract

High-mass stars influence their environment in different ways including feedback via their FUV radiation. The penetration of FUV photons into molecular clouds creates Photon Dominated Regions (PDRs) with different chemical layers where the mainly ionized medium changes into mainly molecular. Different chemical layers in PDRs are traced by different species observable at sub-mm and Far Infrared wavelengths. In this poster we present results from two molecular line surveys. One of them is the James Clerk Maxwell Telescope (JCMT) Spectral Legacy Survey (SLS) toward the luminous (>10^7 L_Sun), massive (~10^6 M_Sun), and distant (11.4 kpc) star-forming region W49A. The SLS images a 2x2 arcminute field toward W49A in the 330-373 GHz frequency range. The detected molecular lines reveal a complex chemistry and the importance of FUV-irradiation in the heating and chemistry of the region. The other line survey presented in the poster is part of the HEXOS (Herschel observations of EXtra-Ordinary Sources, PI: E. Bergin) key program using the Herschel Space Observatory and is toward the nearby (~420 pc) prototypical edge-on Orion Bar PDR and the dense molecular condensation Orion S. Reactive ions, such as CH+, SH+, and CO+, detected as a part of this line survey trace the warm (~500-1000 K) surface region of PDRs. Spectrally resolved HIFI and spectrally unresolved PACS spectra give constraints on the chemistry and excitation of reactive ions in these regions.

Published
2013

32. Origin of CH+ in diffuse molecular clouds: Warm H² and ion-neutral drift.

Author

Valdivia, Valeska, Godard, Benjamin, Hennebelle, Patrick, Gerin, Maryvonne, Lesaffre, Pierre, and Le Bourlot, Jacques

Subjects
MOLECULAR clouds, METHANE analysis, MAGNETIC fields, RELATIVE velocity, MULTIPHASE flow
Abstract

Context. Molecular clouds are known to be magnetised and to display a turbulent and complex structure where warm and cold phases are interwoven. The turbulent motions within molecular clouds transport molecules, and the presence of magnetic fields induces a relative velocity between neutrals and ions known as the ion-neutral drift (vd). These effects all together can influence the chemical evolution of the clouds. Aims: This paper assesses the roles of two physical phenomena which have previously been invoked to boost the production of CH+ under realistic physical conditions: the presence of warm H2 and the increased formation rate due to the ion- neutral drift. Methods: We performed ideal magnetohydrodynamical (MHD) simulations that include the heating and cooling of the multiphase interstellar medium (ISM), and where we treat dynamically the formation of the H2 molecule. In a post-processing step we compute the abundances of species at chemical equilibrium using a solver that we developed. The solver uses the physical conditions of the gas as input parameters, and can also prescribe the H2 fraction if needed. We validate our approach by showing that the H2 molecule generally has a much longer chemical evolution timescale compared to the other species. Results: We show that CH+ is efficiently formed at the edge of clumps, in regions where the H2 fraction is low (0.3-30%) but nevertheless higher than its equilibrium value, and where the gas temperature is high (≱300 K). We show that warm and out of equilibrium H2 increases the integrated column densities of CH+ by one order of magnitude up to values still 3-10 times lower than those observed in the diffuse ISM. We balance the Lorentz force with the ion-neutral drag to estimate the ion-drift velocities from our ideal MHD simulations. We find that the ion-neutral drift velocity distribution peaks around 0.04 km s-1, and that high drift velocities are too rare to have a significant statistical impact on the abundances of CH+. Compared to previous works, our multiphase simulations reduce the spread in vd, and our self-consistent treatment of the ionisation leads to much reduced vd. Nevertheless, our resolution study shows that this velocity distribution is not converged: the ion-neutral drift has a higher impact on CH+ at higher resolution. On the other hand, our ideal MHD simulations do not include ambipolar diffusion, which would yield lower drift velocities. Conclusions: Within these limitations, we conclude that warm H2 is a key ingredient in the efficient formation of CH+ and that the ambipolar diffusion has very little influence on the abundance of CH+ mainly due to the small drift velocities obtained. However, we point out that small-scale processes and other non-thermal processes not included in our MHD simulation may be of crucial importance, and higher resolution studies with better controlled. [ABSTRACT FROM AUTHOR]

Published
2017
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34. HERSCHEL OBSERVATIONS OF INTERSTELLAR CHLORONIUM

Author

Neufeld, David A., Roueff, Evelyne, Snell, Ronald L., Lis, Dariusz, Benz, Arnold O., Bruderer, Simon, Black, John H., De Luca, Massimo, Gerin, Maryvonne, Goldsmith, Paul F., Gupta, Harshal, Indriolo, Nick, Le Bourlot, Jacques, Le Petit, Franck, Larsson, Bengt, Melnick, Gary J., Menten, Karl M., Monje, Raquel, Nagy, Zsofia, Phillips, Thomas G., Sandqvist, Aage, Sonnentrucker, Paule, van der Tak, Floris, Wolfire, Mark G., Neufeld, David A., Roueff, Evelyne, Snell, Ronald L., Lis, Dariusz, Benz, Arnold O., Bruderer, Simon, Black, John H., De Luca, Massimo, Gerin, Maryvonne, Goldsmith, Paul F., Gupta, Harshal, Indriolo, Nick, Le Bourlot, Jacques, Le Petit, Franck, Larsson, Bengt, Melnick, Gary J., Menten, Karl M., Monje, Raquel, Nagy, Zsofia, Phillips, Thomas G., Sandqvist, Aage, Sonnentrucker, Paule, van der Tak, Floris, and Wolfire, Mark G.

Abstract

Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have observed parachloronium (H2Cl+) toward six sources in the Galaxy. We detected interstellar chloronium absorption in foreground molecular clouds along the sight lines to the bright submillimeter continuum sources Sgr A (+50 km s(-1) cloud) and W31C. Both the para-(H2Cl+)-Cl-35 and para-(H2Cl+)-Cl-37 isotopologues were detected, through observations of their 1(11)-0(00) transitions at rest frequencies of 485.42 and 484.23 GHz, respectively. For an assumed ortho-to-para ratio (OPR) of 3, the observed optical depths imply that chloronium accounts for similar to 4%-12% of chlorine nuclei in the gas phase. We detected interstellar chloronium emission from two sources in the Orion Molecular Cloud 1: the Orion Bar photodissociation region and the Orion South condensation. For an assumed OPR of 3 for chloronium, the observed emission line fluxes imply total beam-averaged column densities of similar to 2 x 10(13) cm(-2) and similar to 1.2 x 10(13) cm(-2), respectively, for chloronium in these two sources. We obtained upper limits on the para-(H2Cl+)-Cl-35 line strengths toward H-2 Peak 1 in the Orion Molecular cloud and toward the massive young star AFGL 2591. The chloronium abundances inferred in this study are typically at least a factor similar to 10 larger than the predictions of steady-state theoretical models for the chemistry of interstellar molecules containing chlorine. Several explanations for this discrepancy were investigated, but none has proven satisfactory, and thus the large observed abundances of chloronium remain puzzling., 24

Published
2012
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36. HERSCHELOBSERVATIONS OF INTERSTELLAR CHLORONIUM

Author

Neufeld, David A., primary, Roueff, Evelyne, additional, Snell, Ronald L., additional, Lis, Dariusz, additional, Benz, Arnold O., additional, Bruderer, Simon, additional, Black, John H., additional, De Luca, Massimo, additional, Gerin, Maryvonne, additional, Goldsmith, Paul F., additional, Gupta, Harshal, additional, Indriolo, Nick, additional, Le Bourlot, Jacques, additional, Le Petit, Franck, additional, Larsson, Bengt, additional, Melnick, Gary J., additional, Menten, Karl M., additional, Monje, Raquel, additional, Nagy, Zsófia, additional, Phillips, Thomas G., additional, Sandqvist, Aage, additional, Sonnentrucker, Paule, additional, van der Tak, Floris, additional, and Wolfire, Mark G., additional

Published
2012
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37. HERSCHELMEASUREMENTS OF MOLECULAR OXYGEN IN ORION

Author

Goldsmith, Paul F., primary, Liseau, René, additional, Bell, Tom A., additional, Black, John H., additional, Chen, Jo-Hsin, additional, Hollenbach, David, additional, Kaufman, Michael J., additional, Li, Di, additional, Lis, Dariusz C., additional, Melnick, Gary, additional, Neufeld, David, additional, Pagani, Laurent, additional, Snell, Ronald, additional, Benz, Arnold O., additional, Bergin, Edwin, additional, Bruderer, Simon, additional, Caselli, Paola, additional, Caux, Emmanuel, additional, Encrenaz, Pierre, additional, Falgarone, Edith, additional, Gerin, Maryvonne, additional, Goicoechea, Javier R., additional, Hjalmarson, Åke, additional, Larsson, Bengt, additional, Le Bourlot, Jacques, additional, Le Petit, Franck, additional, De Luca, Massimo, additional, Nagy, Zsofia, additional, Roueff, Evelyne, additional, Sandqvist, Aage, additional, van der Tak, Floris, additional, van Dishoeck, Ewine F., additional, Vastel, Charlotte, additional, Viti, Serena, additional, and Yıldız, Umut, additional

Published
2011
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39. Surface chemistry in the interstellar medium II. H2 formation on dust with random temperature fluctuations.

Author

Bron, Emeric, Le^Bourlot, Jacques, and Le Petit, Franck

Subjects
*HYDROGEN production, *SURFACE chemistry, *INTERSTELLAR medium, *GRAIN dust, *ASTROCHEMISTRY
Abstract

Context. The H2 formation on grains is known to be sensitive to dust temperature, which is also known to fluctuate for small grain sizes due to photon absorption. Aims. We aim at exploring the consequences of simultaneous fluctuations of the dust temperature and the adsorbed H-atom population on the H2 formation rate under the full range of astrophysically relevant UV intensities and gas conditions. Methods. The master equation approach is generalized to coupled fluctuations in both the grain's temperature and its surface population and solved numerically. The resolution can be simplified in the case of the Eley-Rideal mechanism, allowing a fast computation. For the Langmuir-Hinshelwood mechanism, it remains computationally expensive, and accurate approximations are constructed. Results. We find the Langmuir-Hinshelwood mechanism to become an efficient formation mechanism in unshielded photon dominated region edge conditions when taking those fluctuations into account, despite hot average dust temperatures. It reaches an importance comparable to the Eley-Rideal mechanism. However, we show that a simpler rate equation treatment gives qualitatively correct observable results in full cloud simulations under the most astrophysically relevant conditions. Typical differences are a factor of 2-3 on the intensities of the H2 v = 0 lines. We also find that rare fluctuations in cloud cores are sufficient to significantly reduce the formation efficiency. Conclusions. Our detailed analysis confirms that the usual approximations used in numerical models are adequate when interpreting observations, but a more sophisticated statistical analysis is required if one is interested in the details of surface processes. [ABSTRACT FROM AUTHOR]

Published
2014
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41. Gas kinematics around filamentary structures in the Orion B cloud

Author

Mathilde Gaudel, Jan H. Orkisz, Maryvonne Gerin, Jérôme Pety, Antoine Roueff, Antoine Marchal, François Levrier, Marc-Antoine Miville-Deschênes, Javier R. Goicoechea, Evelyne Roueff, Franck Le Petit, Victor de Souza Magalhaes, Pierre Palud, Miriam G. Santa-Maria, Maxime Vono, Sébastien Bardeau, Emeric Bron, Pierre Chainais, Jocelyn Chanussot, Pierre Gratier, Viviana Guzman, Annie Hughes, Jouni Kainulainen, David Languignon, Jacques Le Bourlot, Harvey Liszt, Karin Öberg, Nicolas Peretto, Albrecht Sievers, Pascal Tremblin, Agence Nationale de la Recherche (France), Centre National de la Recherche Scientifique (France), Centre National D'Etudes Spatiales (France), l'Observatoire de Paris, Ministerio de Ciencia, Innovación y Universidades (España), Swedish Research Council, Orkisz, Jan H., Pety, Jérôme, Roueff, Antoine, Marchal, Antoine, Levrier, François, Miville-Deschênes, Marc-Antoine, Goicoechea, Javier R., Roueff, Evelyne, Santa-Maria, Miriam G., Bron, Emeric, Chainais, Pierre, Chanussot, Jocelyn, Gratier, Pierre, Guzman, Viviana, Le Bourlot,Jacques, and Liszt, Harvey

Subjects
ISM: kinematics and dynamics, HII regions, ISM: individual objects: Orion B, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Stars: formation, FOS: Physical sciences, Astronomy and Astrophysics, ISM: clouds, Astrophysics - Astrophysics of Galaxies, Radio lines: ISM
Abstract

39 pags., 78 figs., 2 tabs. 6 apps., Understanding the initial properties of star-forming material and how they affect the star formation process is key. From an observational point of view, the feedback from young high-mass stars on future star formation properties is still poorly constrained. In the framework of the IRAM 30m ORION-B large program, we obtained observations of the translucent and moderately dense gas, which we used to analyze the kinematics over a field of 5 deg^2 around the filamentary structures. We used the ROHSA algorithm to decompose and de-noise the C18O(1-0) and 13CO(1-0) signals by taking the spatial coherence of the emission into account. We produced gas column density and mean velocity maps to estimate the relative orientation of their spatial gradients. We identified three cloud velocity layers at different systemic velocities and extracted the filaments in each velocity layer. The filaments are preferentially located in regions of low centroid velocity gradients. By comparing the relative orientation between the column density and velocity gradients of each layer from the ORION-B observations and synthetic observations from 3D kinematic toy models, we distinguish two types of behavior in the dynamics around filaments: (i) radial flows perpendicular to the filament axis that can be either inflows (increasing the filament mass) or outflows and (ii) longitudinal flows along the filament axis. The former case is seen in the Orion B data, while the latter is not identified. We have also identified asymmetrical flow patterns, usually associated with filaments located at the edge of an HII region. This is the first observational study to highlight feedback from HII regions on filament formation and, thus, on star formation in the Orion B cloud. This simple statistical method can be used for any molecular cloud to obtain coherent information on the kinematics., This work was supported in part by the French Agence Nationale de la Recherche through the DAOISM grant ANR21-CE31-0010 and by the Programme National “Physique et Chimie du Milieu Interstellaire” (PCMI) of CNRS/INSU with INC/INP, co-funded by CEA and CNES. We thank “le centre Jules Jensen” from Observatoire de Paris for its hospitality during the workshops devoted to this project. This research has made use of data from the Herschel Gould Belt Survey (HGBS) project (http: //gouldbelt-herschel.cea.fr). The HGBS is a Herschel Key Programme jointly carried out by SPIRE Specialist Astronomy Group 3 (SAG 3), scientists of several institutes in the PACS Consortium (CEA Saclay, INAF-IFSI Rome and INAF-Arcetri, KU Leuven, MPIA Heidelberg), and scientists of the Herschel Science Center (HSC). J.R.G. and M.G.S.M. thank the Spanish MCIYU for funding support under grant PID2019-106110GB-I00. J.O. acknowledges funding from the Swedish Research Council, grant No. 2017-03864.

Published
2023
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43. Systèmes dynamiques sur réseaux : Applications au milieu interstellaire et à la transition vers la turbulence

Author

Rousseau, Guillaume, Rousseau, Guillaume, 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), Université Paris-Diderot - Paris VII, Le Bourlot Jacques, and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Modélisation physique et simulation numérique, milieu interstellaire, intermittence spatio-temporelle, [PHYS.PHYS]Physics [physics]/Physics [physics], transition vers la turbulence, turbulence, [PHYS.PHYS] Physics [physics]/Physics [physics]
Abstract

The general framework of this thesis is the study and the modeling of spatially-extended systems. We have been more specifically interested by systems where a natural length exists which allows for spatial discretisation. Processes numerically too costly to be incorporated in a continuous model can then be taken into account. Specifically, we have considered the dynamics of dark molecular clouds and the transition to turbulence {\it via} spatio-temporal intermittency. Detailed models of molecular clouds have shown that there is no dominating process in the inner regions. A realistic description must include a hundred of chemical species reacting within a turbulent fluid. Moreover, the local thermal balance imposes the resolution of the radiative transfer equations. We have developed a minimal ``Coupled Map Lattice'' model including those processes at a phenomenological level. Its study has shown that one must consider those processes simultaneously to properly describe the global evolution of the system. In 1986, Y. Pomeau predicted the existence of a specific and ``universal'' scenario for transition to turbulence {\it via} spatio-temporal intermittency. We have studied the role of the propagative structures commonly observed in numerical models and experiments, which can a priori limit the validity of this equivalence between stochastic and deterministic systems. Using a minimal CML model of spatio-temporal intermittency, we have shown that these propagative structures play an active role in the emergence of a specific turbulent regime., Cette thèse a pour cadre général la modélisation et l'étude des systèmes dynamiques étendus. Nous nous sommes plus particulièrement intéressés aux systèmes possédant une longueur naturelle de discrétisation. Les modèles ainsi obtenus offrent la possibilité de tenir compte de processus trop coûteux numériquement dans des modèles continus. Nous avons considéré deux applications : les nuages moléculaires opaques et la transition vers la turbulence par intermittence spatio-temporelle. Les modèles détaillés de nuages moléculaires ont montré que dans ces régions il n'y a pas de processus dominant. Une description réaliste doit inclure une chimie comprenant une centaine d'espèces au sein d'un fluide turbulent dont le bilan thermique local nécessite la résolution des équations du transfert radiatif. Nous avons développé un modèle minimal, de type ``réseau d'itérations couplées'', en nous plaçant à un niveau phénoménologique. L'étude de ce modèle a montré qu'il est indispensable de prendre en compte ces trois aspects pour décrire les processus contrôlant globalement l'évolution de ces systèmes. En 1986, Y. Pomeau prédit l'existence d'un scénario spécifique et ``universel'' de transition vers la turbulence par intermittence spatio-temporelle. Nous avons étudié le rôle des structures propagatives couramment observées dans les simulations numériques et les expériences, qui peuvent a priori limiter la validité de l'équivalence entre systèmes stochastiques et déterministes. Nous avons montré à partir d'un modèle minimal d'intermittence spatio-temporelle, que ces structures propagatives jouent en effet un rôle actif dans l'apparition du régime turbulent spécifique.

Published
1998

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