CO-dark gas and molecular filaments in Milky Way-type galaxies

By Rowan J. Smith, S. Glover, P. C. Clark, Ralf Klessen, Volker Springel. 2014

146 citations recorded by the source corpus.

We use the moving mesh code arepo coupled to a time-dependent chemical network to investigate molecular gas in simulated spiral galaxies that is not traced by CO emission. We calculate H2 and CO column densities, and estimate the CO emission and CO–H2 conversion factor. We find that in conditions akin to those in the local interstellar medium, around 42 per cent of the total molecular mass should be in CO-dark regions, in reasonable agreement with observational estimates. This fraction is almost insensitive to the CO-integrated intensity threshold used to discriminate between CO-bright and CO-dark gas. The CO-dark molecular gas primarily resides in extremely long (>100 pc) filaments that are stretched between spiral arms by galactic shear. Only the centres of these filaments are bright in CO, suggesting that filamentary molecular clouds observed in the Milky Way may only be small parts of much larger structures. The CO-dark molecular gas mainly exists in a partially molecular phase which accounts for a significant fraction of the total disc mass budget. The dark gas fraction is higher in simulations with higher ambient UV fields or lower surface densities, implying that external galaxies with these conditions might have a greater proportion of dark gas

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/ea05961a4cadf559b13cbda572351541e6d1779f

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Citations in the corpus

The SILCC (SImulating the LifeCycle of molecular Clouds) project – I. Chemical evolution of the supernova-driven ISM (2014, methodology): “…(2015) chemistry of H2 within galactic-scale simulations of the ISM (see e.g. Dobbs et al. 2008; Gnedin, Tassis & Kravtsov 2009; Dobbs, Burkert & Pringle 2011; Christensen et al. 2012), and more recently a couple of studies have also treated CO formation (Pettitt et al. 2014; Smith et al. 2014).”
Molecular Clouds in the Milky Way (2015, background): “…be shorter in regions with high gas density that may arise in shells of swept-up atomic gas driven by HII regions, stellar winds, or supernovae or within zones of compressed gas created by shocks of convergent, supersonic gas streams (Glover & Mac Low 2007, Clark et al. 2012, Smith et al. 2014).”
Improving the convergence properties of the moving-mesh code AREPO (2015, background): “G A ] 2014; Genel et al. 2014), as well as in first star formation (e.g. Greif et al. 2011, 2012; Smith et al. 2014), and to a smaller extent in stellar astrophysics (Pakmor et al. 2013) and in problems related to planet formation (Duffell & MacFadyen 2012; Muñoz et al. 2014, 2015).”