The anatomy of the Orion B giant molecular cloud: A local template for studies of nearby galaxies
PETY, Jérôme
Institut de RadioAstronomie Millimétrique [IRAM]
Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
Institut de RadioAstronomie Millimétrique [IRAM]
Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
ORKISZ, Jan
Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
Université Grenoble Alpes [2016-2019] [UGA [2016-2019]]
Institut de RadioAstronomie Millimétrique [IRAM]
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Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
Université Grenoble Alpes [2016-2019] [UGA [2016-2019]]
Institut de RadioAstronomie Millimétrique [IRAM]
PETY, Jérôme
Institut de RadioAstronomie Millimétrique [IRAM]
Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
Institut de RadioAstronomie Millimétrique [IRAM]
Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
ORKISZ, Jan
Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
Université Grenoble Alpes [2016-2019] [UGA [2016-2019]]
Institut de RadioAstronomie Millimétrique [IRAM]
Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
Université Grenoble Alpes [2016-2019] [UGA [2016-2019]]
Institut de RadioAstronomie Millimétrique [IRAM]
GOICOECHEA, Javier
Consejo Superior de Investigaciones Cientificas [España] = Spanish National Research Council [Spain] [CSIC]
< Réduire
Consejo Superior de Investigaciones Cientificas [España] = Spanish National Research Council [Spain] [CSIC]
Langue
en
Article de revue
Ce document a été publié dans
Astronomy and Astrophysics - A&A. 2017, vol. 599, p. A98
EDP Sciences
Résumé en anglais
Context. Molecular lines and line ratios are commonly used to infer properties of extra-galactic star forming regions. The new generation of millimeter receivers almost turns every observation into a line survey. Full ...Lire la suite >
Context. Molecular lines and line ratios are commonly used to infer properties of extra-galactic star forming regions. The new generation of millimeter receivers almost turns every observation into a line survey. Full exploitation of this technical advancement in extra-galactic study requires detailed bench-marking of available line diagnostics.Aims. We aim to develop the Orion B giant molecular cloud (GMC) as a local template for interpreting extra-galactic molecular line observations.Methods. We use the wide-band receiver at the IRAM-30 m to spatially and spectrally resolve the Orion B GMC. The observations cover almost 1 square degree at 26′′ resolution with a bandwidth of 32 GHz from 84 to 116 GHz in only two tunings. Among the mapped spectral lines are the 12CO, 13CO, C18O, C17O, HCN, HNC, 12CN, C2H, HCO+, N2H+(1−0), and 12CS, 32SO, SiO, c - C3H2, CH3OH (2−1) transitions.Results. We introduce the molecular anatomy of the Orion B GMC, including relationships between line intensities and gas column density or far-UV radiation fields, and correlations between selected line and line ratios. We also obtain a dust-traced gas mass that is less than approximately one third the CO-traced mass, using the standard XCO conversion factor. The presence of over-luminous CO can be traced back to the dependence of the CO intensity on UV illumination. As a matter of fact, while most lines show some dependence on the UV radiation field, CN and C2H are the most sensitive. Moreover, dense cloud cores are almost exclusively traced by N2H+. Other traditional high-density tracers, such as HCN(1−0), are also easily detected in extended translucent regions at a typical density of ~500 H2 cm-3. In general, we find no straightforward relationship between line critical density and the fraction of the line luminosity coming from dense gas regions.Conclusions. Our initial findings demonstrate that the relationships between line (ratio) intensities and environment in GMCs are more complicated than often assumed. Sensitivity (i.e., the molecular column density), excitation, and, above all, chemistry contribute to the observed line intensity distributions, and they must be considered together when developing the next generation of extra-galactic molecular line diagnostics of mass, density, temperature, and radiation field.< Réduire
Mots clés en anglais
Astrophysics - Astrophysics of Galaxies
galaxies: ISM
ISM: clouds
HII regions
radio lines: galaxies
astrochemistry
Origine
Importé de halUnités de recherche