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Sökning: onr:"swepub:oai:research.chalmers.se:80592fb7-f295-4186-a4b5-b5d6231a5c19" > Quantitative infere...

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

Gratier, Pierre (författare)
Université de Bordeaux,University of Bordeaux
Pety, Jerome (författare)
Institut de Radioastronomie Millimétrique (IRAM),PSL University Paris
Bron, Emeric (författare)
PSL University Paris
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Roueff, Antoine (författare)
Aix-Marseille Université,Aix Marseille University
Orkisz, Jan, 1991 (författare)
Chalmers tekniska högskola,Chalmers University of Technology
Gerin, Maryvonne (författare)
PSL University Paris
Magalhaes, Victor de Souza (författare)
Institut de Radioastronomie Millimétrique (IRAM)
Gaudel, Mathilde (författare)
PSL University Paris
Vono, Maxime (författare)
Université de Toulouse,University of Toulouse
Bardeau, Sebastien (författare)
Institut de Radioastronomie Millimétrique (IRAM)
Chanussot, Jocelyn (författare)
Université Grenoble Alpes,Grenoble Alpes University
Chainais, Pierre (författare)
Université de Lille,University of Lille
Goicoechea, Javier R. (författare)
CSIC - Instituto de Fisica Fundamental (IFF)
Guzman, Viviana V. (författare)
Pontificia Universidad Catolica de Chile
Hughes, Annie (författare)
Universite Paul Sabatier Toulouse III,Paul Sabatier University
Kainulainen, Jouni, 1979 (författare)
Chalmers tekniska högskola,Chalmers University of Technology
Languignon, David (författare)
PSL University Paris
Le Bourlot, Jacques (författare)
PSL University Paris
Le Petit, Franck (författare)
PSL University Paris
Levrier, Francois (författare)
PSL University Paris
Liszt, Harvey (författare)
National Radio Astronomy Observatory
Peretto, Nicolas (författare)
Cardiff University
Rouefe, Evelyne (författare)
PSL University Paris
Sievers, Albrecht (författare)
Institut de Radioastronomie Millimétrique (IRAM)
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 (creator_code:org_t)
2020-12-23
2021
Engelska.
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 645
Relaterad länk:
https://research.cha... (primary) (free)
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https://www.aanda.or...
https://research.cha...
https://doi.org/10.1...
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  • Tidskriftsartikel (refereegranskat)
Abstract Ämnesord
Stäng  
  • Context. Based on the finding that molecular hydrogen is unobservable in cold molecular clouds, the column density measurements of molecular gas currently rely either on dust emission observation in the far-infrared, which requires space telescopes, or on star counting, which is limited in angular resolution by the stellar density. The (sub)millimeter observations of numerous trace molecules can be effective using ground-based telescopes, but the relationship between the emission of one molecular line and the H-2 column density is non-linear and sensitive to excitation conditions, optical depths, and abundance variations due to the underlying physico- chemistry.Aims. We aim to use multi-molecule line emission to infer the H-2 molecular column density from radio observations.Methods. We propose a data-driven approach to determine the H-2 gas column densities from radio molecular line observations. We use supervised machine-learning methods (random forest) on wide-field hyperspectral IRAM-30m observations of the Orion B molecular cloud to train a predictor of the H-2 column density, using a limited set of molecular lines between 72 and 116 GHz as input, and the Herschel-based dust-derived column densities as "ground truth" output.Results. For conditions similar to those of the Orion B molecular cloud, we obtained predictions of the H-2 column density within a typical factor of 1.2 from the Herschel-based column density estimates. A global analysis of the contributions of the different lines to the predictions show that the most important lines are (CO)-C-13(1-0), (CO)-C-12(1-0), (CO)-O-18(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 that the N2H+(1-0) and CH3OH(2(0)-1(0)) lines be added for the prediction of the H-2 column density in dense core conditions.Conclusions. This article opens a promising avenue for advancing direct inferencing of important physical parameters from the molecular line emission in the millimeter domain. The next step will be to attempt to infer several parameters simultaneously (e.g., the column density and far-UV illumination field) to further test the method.

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
NATURVETENSKAP  -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)
NATURAL SCIENCES  -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)
NATURVETENSKAP  -- Kemi -- Teoretisk kemi (hsv//swe)
NATURAL SCIENCES  -- Chemical Sciences -- Theoretical Chemistry (hsv//eng)

Nyckelord

methods: statistical
ISM: clouds
ISM: molecules

Publikations- och innehållstyp

art (ämneskategori)
ref (ämneskategori)

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