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

• Verfasst von: Glover, Simon [VerfasserIn]
• Verfasst von: Clark, Paul C. [VerfasserIn]
• Titel: Is atomic carbon a good tracer of molecular gas in metal-poor galaxies?
• Verf.angabe: Simon C.O. Glover and Paul C. Clark
• E-Jahr: 2016
• Jahr: March 2016
• Umfang: 14 S.
• Fussnoten: Gesehen am 19.06.2020
• Titel Quelle: Enthalten in: Royal Astronomical SocietyMonthly notices of the Royal Astronomical Society
• Ort Quelle: Oxford : Oxford Univ. Press, 1827
• Jahr Quelle: 2016
• Band/Heft Quelle: 456(2016), Seite 3596-3609
• ISSN Quelle: 1365-2966
• DOI: doi:10.1093/mnras/stv2863
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: galaxies: ISM
• Sach-SW: ISM: clouds
• Sach-SW: ISM: molecules
• Sach-SW: stars: formation
• K10plus-PPN: 1701106981

Abstract

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.