Dark Molecular Gas in Simulations of z - 0 Disk Galaxies
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Li, Qi; Narayanan, Desika; Dave, Romeel; Krumholz, Mark
Description
The H2 mass of molecular clouds has traditionally been traced by the CO(J = 1−0) rotational transition line. This said, CO is relatively easily photodissociated and can also be destroyed by cosmic rays, thus rendering some fraction of molecular gas to be "CO-dark." We investigate the amount and physical properties of CO-dark gas in two z ~ 0 disk galaxies and develop predictions for the expected intensities of promising alternative tracers ([C i] 609 μm and [C ii] 158 μm emission). We do this...[Show more]
dc.contributor.author | Li, Qi | |
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dc.contributor.author | Narayanan, Desika | |
dc.contributor.author | Dave, Romeel | |
dc.contributor.author | Krumholz, Mark | |
dc.date.accessioned | 2019-12-09T04:48:23Z | |
dc.date.available | 2019-12-09T04:48:23Z | |
dc.identifier.issn | 0004-637X | |
dc.identifier.uri | http://hdl.handle.net/1885/188702 | |
dc.description.abstract | The H2 mass of molecular clouds has traditionally been traced by the CO(J = 1−0) rotational transition line. This said, CO is relatively easily photodissociated and can also be destroyed by cosmic rays, thus rendering some fraction of molecular gas to be "CO-dark." We investigate the amount and physical properties of CO-dark gas in two z ~ 0 disk galaxies and develop predictions for the expected intensities of promising alternative tracers ([C i] 609 μm and [C ii] 158 μm emission). We do this by combining cosmological zoom simulations of disk galaxies with thermal-radiative-chemical equilibrium interstellar medium (ISM) calculations to model the predicted H i and H2 abundances and CO (J = 1−0), [C i] 609 μm, and [C ii] 158 μm emission properties. Our model treats the ISM as a collection of radially stratified clouds whose properties are dictated by their volume and column densities, the gas-phase metallicity, and the interstellar radiation field (ISRF) and CR ionization rates. Our main results follow. Adopting an observationally motivated definition of CO-dark gas, i.e., H2 gas with W CO < 0.1 K km s−1, we find that a significant amount (gsim50%) of the total H2 mass lies in CO-dark gas, most of which is diffuse gas, poorly shielded due to low dust column density. The CO-dark molecular gas tends to be dominated by [C ii], though [C i] also serves as a bright tracer of the dark gas in many instances. At the same time, [C ii] also tends to trace neutral atomic gas. As a result, when we quantify the conversion factors for the three carbon-based tracers of molecular gas, we find that [C i] suffers the least contamination from diffuse atomic gas and is relatively insensitive to secondary parameters. | |
dc.description.sponsorship | Q.L. was funded by NSF grant AST-1724864. D.N. acknowledges funding from NSF grants AST-1724864 and AST-1715206 and HST AR-13906.001 from the Space Telescope Science Institute. M.R.K. acknowledges support from the Australian Research Council’s Discovery Projects funding scheme, grant DP160100695. | |
dc.format.mimetype | application/pdf | |
dc.language.iso | en_AU | |
dc.publisher | IOP Publishing | |
dc.rights | © 2018 The American Astronomical Society. | |
dc.source | The Astrophysical Journal | |
dc.subject | astrochemistry | |
dc.subject | galaxies: ISM | |
dc.subject | ISM: molecules | |
dc.subject | methods: numerical | |
dc.title | Dark Molecular Gas in Simulations of z - 0 Disk Galaxies | |
dc.type | Journal article | |
local.description.notes | Imported from ARIES | |
local.identifier.citationvolume | 869 | |
dcterms.dateAccepted | 2018-10-25 | |
dc.date.issued | 2018-12-13 | |
local.identifier.absfor | 020103 - Cosmology and Extragalactic Astronomy | |
local.identifier.ariespublication | u3102795xPUB140 | |
local.publisher.url | https://iopscience.iop.org/ | |
local.type.status | Published Version | |
local.contributor.affiliation | Li, Qi, University of Florida | |
local.contributor.affiliation | Narayanan, Desika, University of Florida | |
local.contributor.affiliation | Dave, Romeel, University of the Western Cape | |
local.contributor.affiliation | Krumholz, Mark, College of Science, ANU | |
dc.relation | http://purl.org/au-research/grants/arc/DP160100695 | |
local.bibliographicCitation.issue | 73 | |
local.bibliographicCitation.startpage | 1 | |
local.bibliographicCitation.lastpage | 14 | |
local.identifier.doi | 10.3847/1538-4357/aaec77 | |
local.identifier.absseo | 970102 - Expanding Knowledge in the Physical Sciences | |
dc.date.updated | 2019-07-28T08:17:56Z | |
local.identifier.scopusID | 2-s2.0-85058449807 | |
dcterms.accessRights | Open Access | |
dc.provenance | http://sherpa.ac.uk/romeo/issn/0004-637X/..."author can archive publisher's version/PDF" from SHERPA/RoMEO site (as at 9/12/19) | |
Collections | ANU Research Publications |
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