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1. 3D chemical structure of diffuse turbulent ISM. I. Statistics of the HI-to-H$_2$ transition

Author

Bellomi, Elena, Godard, Benjamin, Hennebelle, Patrick, Valdivia, Valeska, Forêts, Guillaume Pineau des, Lesaffre, Pierre, and Pérault, Michel

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We studied the statistical properties of the HI-to-H$_2$ transition observed in absorption in the local diffuse and multiphase ISM to identify the physical processes controlling the probability of occurrence of any line of sight. The turbulent diffuse ISM is modeled using the RAMSES code, which includes detailed treatments of the magnetohydrodynamics, the thermal evolution of the gas, and the chemistry of H$_2$. The impacts of the UV radiation field, the mean density, the turbulent forcing, the integral scale, the magnetic field, and the gravity on the molecular content of the gas are explored through a parametric study covering a wide range of physical conditions. The statistics of the HI-to-H$_2$ transition are interpreted through analytical prescriptions and compared with the observations using a modified and robust version of the Kolmogorov-Smirnov test. The results of one simulation, convolved with the distribution of distances of the observational sample, are able to explain most of the statistical properties of the HI-to-H$_2$ transition observed in the local ISM. The tightest agreement is obtained for a neutral diffuse gas modeled over ~200 pc, with a mean density of $1-2$ cm$^{-3}$, illuminated by the standard interstellar UV radiation field, and stirred up by a large-scale compressive turbulent forcing. Within this configuration, the 2D probability histogram of the column densities of H and H$_2$ is remarkably stable and is almost unaltered by gravity, the strength of the turbulent forcing, the resolution of the simulation, or the strength of the magnetic field $B_x$. The weak effect of the resolution and our analytical prescription suggest that the column densities of HI are likely built up in large-scale WNM and CNM structures correlated in density over ~20 pc and ~10 pc, respectively, while those of H$_2$ are built up in CNM structures between ~3 pc and ~10 pc.

Published
2020
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2. Interstellar OH+, H2O+ and H3O+ along the sight-line to G10.6-0.4

Author

Gerin, Maryvonne, De Luca, M., Black, John, Herbst, Eric, Goicoechea, Javier R., Falgarone, Edith, Godard, Benjamin, Pearson, John C., Lis, Dariucz C., Phillips, Thomas G., Bell, Thomas A., Sonnentrucker, Paule, Boulanger, Francois, Cernicharo, José, Coutens, Audrey, Dartois, Emmanuel, Encrenaz, Pierre, Giesen, Thomas, Goldsmith, Paul F., Gupta, Harshal, Gry, Cecile, Hennebelle, Patrick, Hily-Blant, Pierre, Joblin, Christine, Kazmierczak, Maja, Kolos, Robert, Krelowski, Jacek, Martin-Pintado, Jesus, Monje, Raquel, Mookerjea, Bhaswati, Pérault, Michel, Persson, Carina, Plume, René, Rimmer, Paul B., Salez, Morvan, Schmidt, Mirisloaw, Teyssier, David, Vastel, Charlotte, Yu, Shan Shan, Contursi, Alessandra, Menten, Karl, Geballe, Thomas, Schlemmer, Stephan, Shipman, Russ, Tielens, Alexander G. G. M., Philipp-May, Sabine, Cros, Alain, Zmuidzinas, Jonas, Samoska, L. A, Klein, K., Neufeld, D. A., Lorenzani, A., and Stutzki, Jürgen

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We report the detection of absorption lines by the reactive ions OH+, H2O+ and H3O+ along the line of sight to the submillimeter continuum source G10.6$-$0.4 (W31C). We used the Herschel HIFI instrument in dual beam switch mode to observe the ground state rotational transitions of OH+ at 971 GHz, H2O+ at 1115 and 607 GHz, and H3O+ at 984 GHz. The resultant spectra show deep absorption over a broad velocity range that originates in the interstellar matter along the line of sight to G10.6$-$0.4 as well as in the molecular gas directly associated with that source. The OH+ spectrum reaches saturation over most velocities corresponding to the foreground gas, while the opacity of the H2O+ lines remains lower than 1 in the same velocity range, and the H3O+ line shows only weak absorption. For LSR velocities between 7 and 50 kms$^{-1}$ we estimate total column densities of $N$(OH+) $> 2.5 \times 10^{14}$ cm$^{-2}$, $N$(H2O+) $\sim 6 \times 10^{13}$ cm$^{-2}$ and $N$(H3O+) $\sim 4.0 \times 10^{13}$ cm$^{-2}$. These detections confirm the role of O$^+$ and OH$^+$ in initiating the oxygen chemistry in diffuse molecular gas and strengthen our understanding of the gas phase production of water. The high ratio of the OH+ by the H2O+ column density implies that these species predominantly trace low-density gas with a small fraction of hydrogen in molecular form.

Published
2010
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3. Radio-millimetre investigation of galactic infrared dark clouds

Author

Teyssier, David, Hennebelle, Patrick, and Perault, Michel

Subjects
Astrophysics
Abstract

This paper presents follow-up observations of the mid-Infrared dark clouds selected from the ISOGAL inner Galaxy sample. On-the-fly maps of 13CO, C18O and the 1.2 mm continuum emission have been obtained a the IRAM 30-m telescope. A preliminary analysis of the physico-chemical conditions at works in the clouds is given and molecular depletion onto cold grains is discussed., Comment: 16 pages, 12 figures, to be published in A&A

Published
2001
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4. A post-iras interstellar dust model

Author

Desert, Francois-Xavier, Boulanger, Francois, Pérault, Michel, Araki, H., editor, Ehlers, J., editor, Hepp, K., editor, Kippenhahn, R., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, and Lawrence, Andrew, editor

Published
1988
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6. The recent formation of massive stars in the Galactic Center region

Author

Schuller, Frederic, Menten, Karl, Bertoldi, Frank, Polehampton, Edward, Wyrowski, Friedrich, Omont, Alain, Maillard, Jean-Pierre, Moneti, Andrea, Perault, Michel, Zavagno, Annie, Burgdorf, Martin, Blommaert, Joris, Glass, Ian, and Beaussier, Catherine

Subjects
[SDU] Sciences of the Universe [physics]
Published
2004

7. The Herschel-Heterodyne Instrument for the Far-Infrared (HIFI): instrument and pre-launch testing

Author

Oschmann, Jacobus M., Jr., de Graauw, Mattheus W. M., MacEwen, Howard A., de Graauw, Thijs, Whyborn, Nick, Helmich, Frank, Dieleman, Pieter, Roelfsema, Peter, Caux, Emmanuel, Phillips, Tom, Stutzki, Jürgen, Beintema, Douwe, Benz, Arnold, Biver, Nicolas, Boogert, Adwin, Boulanger, Francois, Cherednichenko, Sergey, Coeur-Joly, Odile, Comito, Claudia, Dartois, Emmanuel, de Jonge, Albrecht, de Lange, Gert, Delorme, Ian, DiGiorgio, Anna, Dubbeldam, Luc, Edwards, Kevin, Fich, Michael, Güsten, Rolf, Herpin, Fabrice, Honingh, Netty, Huisman, Robert, Jacobs, Herman, Jellema, Willem, Kawamura, Jon, Kester, Do, Klapwijk, Teun, Klein, Thomas, Kooi, Jacob, Krieg, Jean-Michel, Kramer, Carsten, Kruizenga, Bob, Laauwen, Wouter, Larsson, Bengt, Leinz, Christian, Liseau, Rene, Lord, Steve, Luinge, Willem, Marston, Anthony, Merkel, Harald, Moreno, Rafael, Morris, Patrick, Murphy, Anthony, Naber, Albert, Planesas, Pere, Martin-Pintado, Jesus, Olberg, Micheal, Orleanski, Piotr, Ossenkopf, Volker, Pearson, John, Perault, Michel, Phillip, Sabine, Rataj, Mirek, Ravera, Laurent, Saraceno, Paolo, Schieder, Rudolf, Schmuelling, Frank, Szczerba, Ryszard, Shipman, Russell, Teyssier, David, Vastel, Charlotte, Visser, Huib, Wildeman, Klaas, Wafelbakker, Kees, Ward, John, Higgins, Roonan, Aarts, Henri, Tielens, Xander, Zaal, Peer, Oschmann, Jacobus M., Jr., de Graauw, Mattheus W. M., MacEwen, Howard A., de Graauw, Thijs, Whyborn, Nick, Helmich, Frank, Dieleman, Pieter, Roelfsema, Peter, Caux, Emmanuel, Phillips, Tom, Stutzki, Jürgen, Beintema, Douwe, Benz, Arnold, Biver, Nicolas, Boogert, Adwin, Boulanger, Francois, Cherednichenko, Sergey, Coeur-Joly, Odile, Comito, Claudia, Dartois, Emmanuel, de Jonge, Albrecht, de Lange, Gert, Delorme, Ian, DiGiorgio, Anna, Dubbeldam, Luc, Edwards, Kevin, Fich, Michael, Güsten, Rolf, Herpin, Fabrice, Honingh, Netty, Huisman, Robert, Jacobs, Herman, Jellema, Willem, Kawamura, Jon, Kester, Do, Klapwijk, Teun, Klein, Thomas, Kooi, Jacob, Krieg, Jean-Michel, Kramer, Carsten, Kruizenga, Bob, Laauwen, Wouter, Larsson, Bengt, Leinz, Christian, Liseau, Rene, Lord, Steve, Luinge, Willem, Marston, Anthony, Merkel, Harald, Moreno, Rafael, Morris, Patrick, Murphy, Anthony, Naber, Albert, Planesas, Pere, Martin-Pintado, Jesus, Olberg, Micheal, Orleanski, Piotr, Ossenkopf, Volker, Pearson, John, Perault, Michel, Phillip, Sabine, Rataj, Mirek, Ravera, Laurent, Saraceno, Paolo, Schieder, Rudolf, Schmuelling, Frank, Szczerba, Ryszard, Shipman, Russell, Teyssier, David, Vastel, Charlotte, Visser, Huib, Wildeman, Klaas, Wafelbakker, Kees, Ward, John, Higgins, Roonan, Aarts, Henri, Tielens, Xander, and Zaal, Peer

Abstract

This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI), to be launched onboard of ESA's Herschel Space Observatory, by 2008. It includes the first results from the instrument level tests. The instrument is designed to be electronically tuneable over a wide and continuous frequency range in the Far Infrared, with velocity resolutions better than 0.1 km/s with a high sensitivity. This will enable detailed investigations of a wide variety of astronomical sources, ranging from solar system objects, star formation regions to nuclei of galaxies. The instrument comprises 5 frequency bands covering 480-1150 GHz with SIS mixers and a sixth dual frequency band, for the 1410-1910 GHz range, with Hot Electron Bolometer Mixers (HEB). The Local Oscillator (LO) subsystem consists of a dedicated Ka-band synthesizer followed by 7 times 2 chains of frequency multipliers, 2 chains for each frequency band. A pair of Auto-Correlators and a pair of Acousto-Optic spectrometers process the two IF signals from the dual-polarization front-ends to provide instantaneous frequency coverage of 4 GHz, with a set of resolutions (140 kHz to 1 MHz), better than < 0.1 km/s. After a successful qualification program, the flight instrument was delivered and entered the testing phase at satellite level. We will also report on the pre-flight test and calibration results together with the expected in-flight performance.

Published
2008

8. The Herschel-Heterodyne Instrument for the Far-Infrared (HIFI): instrument and pre-launch testing

Author

de Graauw, Thijs, primary, Whyborn, Nick, additional, Helmich, Frank, additional, Dieleman, Pieter, additional, Roelfsema, Peter, additional, Caux, Emmanuel, additional, Phillips, Tom, additional, Stutzki, Jürgen, additional, Beintema, Douwe, additional, Benz, Arnold, additional, Biver, Nicolas, additional, Boogert, Adwin, additional, Boulanger, Francois, additional, Cherednichenko, Sergey, additional, Coeur-Joly, Odile, additional, Comito, Claudia, additional, Dartois, Emmanuel, additional, de Jonge, Albrecht, additional, de Lange, Gert, additional, Delorme, Ian, additional, DiGiorgio, Anna, additional, Dubbeldam, Luc, additional, Edwards, Kevin, additional, Fich, Michael, additional, Güsten, Rolf, additional, Herpin, Fabrice, additional, Honingh, Netty, additional, Huisman, Robert, additional, Jacobs, Herman, additional, Jellema, Willem, additional, Kawamura, Jon, additional, Kester, Do, additional, Klapwijk, Teun, additional, Klein, Thomas, additional, Kooi, Jacob, additional, Krieg, Jean-Michel, additional, Kramer, Carsten, additional, Kruizenga, Bob, additional, Laauwen, Wouter, additional, Larsson, Bengt, additional, Leinz, Christian, additional, Liseau, Rene, additional, Lord, Steve, additional, Luinge, Willem, additional, Marston, Anthony, additional, Merkel, Harald, additional, Moreno, Rafael, additional, Morris, Patrick, additional, Murphy, Anthony, additional, Naber, Albert, additional, Planesas, Pere, additional, Martin-Pintado, Jesus, additional, Olberg, Micheal, additional, Orleanski, Piotr, additional, Ossenkopf, Volker, additional, Pearson, John, additional, Perault, Michel, additional, Phillip, Sabine, additional, Rataj, Mirek, additional, Ravera, Laurent, additional, Saraceno, Paolo, additional, Schieder, Rudolf, additional, Schmuelling, Frank, additional, Szczerba, Ryszard, additional, Shipman, Russell, additional, Teyssier, David, additional, Vastel, Charlotte, additional, Visser, Huib, additional, Wildeman, Klaas, additional, Wafelbakker, Kees, additional, Ward, John, additional, Higgins, Roonan, additional, Aarts, Henri, additional, Tielens, Xander, additional, and Zaal, Peer, additional

Published
2008
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11. Development of ISOCAM: the camera of the Infrared Space Observatory

Author

Cesarsky, Catherine J., primary, Bonnal, Jean-Francois, additional, Boulade, Olivier, additional, Cretolle, Jacky B., additional, Imbault, Daniele, additional, Lapegue, Jacques, additional, Rio, Yvon, additional, Vigroux, Laurent G., additional, Sibille, Francois, additional, Epstein, Gerard, additional, Lacombe, Francois, additional, Puget, Pascal, additional, Rouan, Daniel, additional, Saint-Pe, Olivier, additional, Tiphene, Didier, additional, Cesarsky, Diego A., additional, Perault, Michel, additional, Davies, John K., additional, Purkins, Terry, additional, Nordh, H. Lennart, additional, Olofsson, Goran, additional, and Ventura, Giulio, additional

Published
1993
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14. Numerical study of the effective viscosity and pressure in perturbed turbulent flows.

Author

Panis, Jean-Francois and Perault, Michel

Subjects
*TURBULENCE, *VISCOSITY, *FLUID dynamics
Abstract

Presents a numerical investigation of the linear response of a turbulent flow to a perturbation at large scale. Corresponding of part of the small scale action to the standard turbulent viscosity; Creation of a turbulent pressure force which resists compression; Estimation of an adiabatic index for the turbulent pressure.

Published
1998
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15. Etalonnage de Herschel/HIFI : approche système et expérimentale d'un instrument scientifique spatial. Etude observationnelle de coeurs denses galactiques

Author

Teyssier, David, 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), Université Pierre et Marie Curie - Paris VI, Perault Michel, Teyssier, david, and École normale supérieure - Paris (ENS-PSL)

Subjects
Herschel Space Observatory, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Etalonnage, Instrumentation spatiale, Milieu interstellaire, Formation d'etoiles, Spectroscopie, Nuages moleculaires denses, [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph], Radioastronomie submillimetrique
Abstract

The calibration of a remote-sensing instrument for the observation of the Earth or of the Cosmos is a key to the highest scientific return from the experiment. In the first part of this thesis, we initiate the preparation of the calibration tools and methods for the submillimetre spectrometer HIFI on board the Herschel satellite. The first aspect concentrates on the data calibration and their convertion into a physical scale. We first collect the requirements of the in-flight calibration and identify the primary and secondary calibrators. We then build a list of potential candidates, complemented by a ground-based preparatory observation campaign. We study the current internal calibration scheme based on two internal loads, and present a first error budget on the HIFI measurements. We show that this approach is {\it a priori} not adapted to the space conditions, and we give the preliminary elements of a best-suited calibration technique. The second point of this calibration work focusses on the instrument calibration in itself. We analyse the needs of the laboratory measurement campaign of the first HIFI prototype and propose an original system allowing to calibrate various instrumental parameters on the ground. We also show the importance of an instrumental modelling work, and present a description of the standing wave systems expected to affect the HIFI data. The second part of this thesis is dedicated to the study of dense galactic cores detected in the mid-infrared by the ISO satellite. We show that these objets belong to a new population of massive (M > 1000 solar masses) and cold (8 < T < 25 K) condensations associated to giant molecular clouds. Our analysis indicates visible extinction in excess of 50, and suggests that depletion onto grains affects most of the molecular species. We also show that these objets are fragmented, and that they are very likely future, if not already initiated, progenitor sites of high mass stars., L'étalonnage des instruments dédiés à l'observation de la Terre et du Cosmos est l'une des clefs d'un retour scientifique maximal de ces missions. La première partie de cette thèse est consacrée à la préparation des outils et méthodes d'étalonnage du spectromètre submillimétrique HIFI embarqué à bord du satellite Herschel en 2007. Le premier aspect traite de l'étalonnage des données et de leur conversion en une échelle scientifique. Nous recensons dans un premier temps les besoins de l'étalonnage en vol et identifions les étalons primaires et secondaires. Nous établissons alors une liste de candidats potentiels, complétée par une campagne d'observations préparatoires au sol. Un schéma d'étalonnage interne fondé sur deux charges embarquées est étudié et nous présentons un premier bilan d'erreur. Nous montrons que cette approche n'est a priori pas adaptée aux conditions spatiales et donnons les premiers éléments d'une technique plus adéquate. Le second aspect s'intéresse à l'étalonnage de l'instrument proprement dit. Nous analysons les besoins de la campagne de mesures en laboratoire du premier prototype de HIFI, et proposons un système original afin d'étalonner divers paramètres au sol. Nous montrons également l'importance d'une modélisation instrumentale et présentons une description des systèmes d'ondes stationnaires susceptibles d'affecter les données de HIFI. La seconde partie de cette thèse est dédiée à l'étude de coeurs denses galactiques détectés dans l'infrarouge moyen par le satellite ISO. Nous montrons que ces objets appartiennent à une population nouvelle de condensations massives (M > 1000 Masses solaires) et froides (8 < T < 25 K) associées à des nuages moléculaires géants. L'analyse indique des extinctions dans le visible supérieures à 50, et suggère que des phénomènes de collage sur les grain affectent la plupart des espèces moléculaires. Nous montrons que ces objets sont probablement fragementés, et qu'ils sont susceptibles, ou ont déjà initié la formation d'étoiles massives en leur sein.

Published
2002

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