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The molecular gas r...
The molecular gas reservoir of 6 low-metallicity galaxies from the Herschel Dwarf Galaxy Survey A ground-based follow-up survey of CO(1-0), CO(2-1), and CO(3-2)
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- Cormier, D. (author)
- Ruprecht-Karls-Universität Heidelberg,Heidelberg University
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- Madden, S. C. (author)
- Centre national de la recherche scientifique (CNRS)
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- Lebouteiller, V. (author)
- Centre national de la recherche scientifique (CNRS)
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- Hony, S. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Aalto, Susanne, 1964 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Costagliola, Francesco, 1981 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Hughes, A. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Remy-Ruyer, A. (author)
- Centre national de la recherche scientifique (CNRS)
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- Abel, N. (author)
- University of Cincinnati
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- Bayet, E. (author)
- University Of Oxford
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- Bigiell, F. (author)
- Ruprecht-Karls-Universität Heidelberg,Heidelberg University
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- Cannon, J. M. (author)
- Macalester College
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- Cumming, Robert, 1967 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Galametz, M. (author)
- University Of Cambridge
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- Galliano, F. (author)
- Centre national de la recherche scientifique (CNRS)
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- Viti, S. (author)
- University College London (UCL)
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- Wu, R. (author)
- Centre national de la recherche scientifique (CNRS)
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(creator_code:org_t)
- 2014-04-17
- 2014
- English.
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 564
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Abstract
Subject headings
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- Context. Observations of nearby starburst and spiral galaxies have revealed that molecular gas is the driver of star formation. However, some nearby low-metallicity dwarf galaxies are actively forming stars, but CO, the most common tracer of this reservoir, is faint, leaving us with a puzzle about how star formation proceeds in these environments. Aims. We aim to quantify the molecular gas reservoir in a subset of 6 galaxies from the Herschel Dwarf Galaxy Survey with newly acquired CO data and to link this reservoir to the observed star formation activity. Methods. We present CO(1-0), CO(2-1), and CO(3-2) observations obtained at the ATNE Mopra 22-m, APEX, and IRAM 30-m telescopes, as well as [CII] 157 mu m and [OI] 63 mu m observations obtained with the Herschel/PACS spectrometer in the 6 low-metallicity dwarf galaxies: Haro 11, Mrk 1089, Mrk 930, NGC 4861, NGC 625, and UM 311. We derived their molecular gas masses from several methods, including using the CO-to-H-2 conversion factor X-CO (both Galactic and metallicity-scaled values) and dust measurements. The molecular and atomic gas reservoirs were compared to the star formation activity. We also constrained the physical conditions of the molecular clouds using the non-LTE code RADEX and the spectral synthesis code Cloudy. Results. We detect CO in 5 of the 6 galaxies, including first detections in Haro 11 (Z similar to 0.4 Z(circle dot)), Mrk 930 (0.2 Z(circle dot)), and UM 311 (0.5 Z(circle dot)), but CO remains undetected in NGC 4861 (0.2 Z(circle dot)). The CO luminosities are low, while [CII] is bright in these galaxies, resulting in [CII]/CO(1-0) >= 10 000. Our dwarf galaxies are in relatively good agreement with the Schmidt-Kennicutt relation for total gas. They show short molecular depletion timescales, even when considering metallicity-scaled X-CO factors. Those galaxies are dominated by their HI gas, except Haro 11, which has high star formation efficiency and is dominated by ionized and molecular gas. We determine the mass of each ISM phase in Haro 11 using Cloudy and estimate an equivalent X-CO factor that is 10 times higher than the Galactic value. Overall, our results confirm the emerging picture that CO suffers from significant selective photodissociation in low-metallicity dwarf galaxies.
Subject headings
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Keyword
- CCONI LJ
- NEARBY
- infrared: galaxies
- ISM: molecules
- V322
- ASTROPHYSICAL JOURNAL
- V373
- CO-TO-H-2 CONVERSION FACTOR
- LARGE-MAGELLANIC-CLOUD
- 1995
- P423
- ASTROPHYSICAL JOURNAL
- radio lines: galaxies
- galaxies: dwarf
- V454
- P293
- ASTROPHYSICAL JOURNAL
- INTERSTELLAR-MEDIUM
- C-II LINE
- GLITSCH A
- SPITZER-SPACE-TELESCOPE
- 1987
- galaxies: ISM
- ALPHA VELOCITY-FIELDS
- P681
- STAR-FORMING GALAXIES
- 1991
- GALAXIES
- LMC-N 11
- BLUE COMPACT GALAXIES
- ACEY GJ
Publication and Content Type
- art (subject category)
- ref (subject category)
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- By the author/editor
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Cormier, D.
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Madden, S. C.
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Lebouteiller, V.
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Hony, S.
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Aalto, Susanne, ...
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Costagliola, Fra ...
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show more...
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Hughes, A.
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Remy-Ruyer, A.
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Abel, N.
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Bayet, E.
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Bigiell, F.
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Cannon, J. M.
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Cumming, Robert, ...
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Galametz, M.
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Galliano, F.
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Viti, S.
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Wu, R.
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- NATURAL SCIENCES
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Chalmers University of Technology