A Global View of Molecule-Forming Clouds in the Galaxy

Gibson, Steven J.; Howard, Ward S.; Jolly, Christian; Newton, J.; Bell, Aaron C.; Spraggs, M. E.; Hughes, J. Marcus; Tagliaboschi, Aaron M.; Brunt, Christopher M.; Taylor, A. R.; Stil, J. M.; Dame, T. M.

doi:10.1017/s1743921316007882

Cited by 1 publication

(1 citation statement)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In such an environment, the time-scale of gravitational collapse is longer than the time-scale of the relevant chemical reactions. However, if the dust-to-gas ratio is much lower than the Milky Way value, non-equilibrium treatment could be desirable, especially for small-scale structures (Gibson et al 2016;Hu et al 2016;Pallottini et al 2017). The argument of non-equilibrium depends strongly on the lifetime or the sustaining mechanism of dense clouds.…”

Section: H 2 Abundancementioning

confidence: 99%

Populating H2 and CO in galaxy simulation with dust evolution

Chen

Hirashita

Hou

et al. 2017

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

There are two major theoretical issues for the star formation law (the relation between the surface densities of molecular gas and star formation rate on a galaxy scale): (i) At low metallicity, it is not obvious that star-forming regions are rich in H 2 because the H 2 formation rate depends on the dust abundance; and (ii) whether or not CO really traces H 2 is uncertain, especially at low metallicity. To clarify these issues, we use a hydrodynamic simulation of an isolated disc galaxy with a spatial resolution of a few tens parsecs. The evolution of dust abundance and grain size distribution is treated consistently with the metal enrichment and the physical state of the interstellar medium. We compute the H 2 and CO abundances using a subgrid post-processing model based on the dust abundance and the dissociating radiation field calculated in the simulation. We find that when the metallicity is 0.4 Z ⊙ (t < 1 Gyr), H 2 is not a good tracer of star formation rate because H 2 -rich regions are limited to dense compact regions. At Z 0.8 Z ⊙ , a tight star formation law is established for both H 2 and CO. At old (t ∼ 10 Gyr) ages, we also find that adopting the so-called MRN grain size distribution with an appropriate dust-to-metal ratio over the entire disc gives reasonable estimates for the H 2 and CO abundances. For CO, improving the spatial resolution of the simulation is important while the H 2 abundance is not sensitive to sub-resolution structures at Z 0.4 Z ⊙ .

show abstract

Section: H 2 Abundancementioning

confidence: 99%