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Is atomic carbon a good tracer of molecular gas in metal-poor galaxies?

Carbon monoxide (CO) is widely used as a tracer of molecular hydrogen (H2) in metal-rich galaxies, but is known to become - ineffective in low-metallicity dwarf galaxies. Atomic carbon has been suggested as a superior tracer of H2 in these metal-poor systems, but its suitability remains unproven. To...

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Bibliographic Details
Main Authors: Glover, Simon (Author) , Clark, Paul C. (Author)
Format: Article (Journal)
Language:English
Published: March 2016
In: Monthly notices of the Royal Astronomical Society
Year: 2016, Volume: 456, Pages: 3596-3609
ISSN:1365-2966
DOI:10.1093/mnras/stv2863
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1093/mnras/stv2863
Verlag, lizenzpflichtig, Volltext: http://adsabs.harvard.edu/abs/2016MNRAS.456.3596G
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Author Notes:Simon C.O. Glover and Paul C. Clark
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Summary:Carbon monoxide (CO) is widely used as a tracer of molecular hydrogen (H2) in metal-rich galaxies, but is known to become - ineffective in low-metallicity dwarf galaxies. Atomic carbon has been suggested as a superior tracer of H2 in these metal-poor systems, but its suitability remains unproven. To help us to assess how well atomic carbon traces H2 at low metallicity, we have performed a series of numerical simulations of turbulent molecular clouds that cover a wide range of different metallicities. Our - simulations demonstrate that in star-forming clouds, the conversion factor between [C I] emission and H2 mass, XCI, scales approximately as XCI ∝ Z-1. We recover a similar scaling for the CO-to-H2 conversion factor, XCO, but find that at this point in the evolution of the clouds, XCO is consistently smaller than XCI, by a factor of a few or more. We have also examined how XCI and XCO evolve with time. We find that XCI does not vary strongly with time, demonstrating that atomic carbon remains a good tracer of H2 in metal-poor systems even at times - significantly before the onset of star formation. On the other hand, XCO varies very strongly with time in metal-poor clouds, showing that CO does not trace H2 well in starless clouds at low metallicity.
Item Description:Gesehen am 19.06.2020
Physical Description:Online Resource
ISSN:1365-2966
DOI:10.1093/mnras/stv2863

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