The properties of the interstellar medium in disc galaxies with stellar feedback

Abstract

We perform calculations of isolated disc galaxies to investigate how the properties of the interstellar medium (ISM), the nature of molecular clouds and the global star formation rate depend on the level of stellar feedback. We adopt a simple physical model, which includes a galactic potential, a standard cooling and heating prescription of the ISM and self‐gravity of the gas. Stellar feedback is implemented by injecting energy into dense, gravitationally collapsing gas, but is independent of the Schmidt–Kennicutt relation. We obtain fractions of gas, and filling factors for different phases of the ISM in reasonable agreement with observations. Supernovae are found to be vital to reproduce the scaleheights of the different components of the ISM, and velocity dispersions. The giant molecular clouds (GMCs) formed in the simulations display mass spectra similar to the observations, their normalization depend on the level of feedback. We find ∼40 per cent of the clouds exhibit retrograde rotation, induced by cloud–cloud collisions. The star formation rates we obtain are in good agreement with the observed Schmidt–Kennicutt relation, and are not strongly depend on the star formation efficiency we assume, being largely self‐regulated by the feedback. We also investigate the effect of spiral structure by comparing calculations with and without the spiral component of the potential. The main difference with a spiral potential is that more massive GMCs are able to accumulate in the spiral arms. Thus we are able to reproduce massive GMCs, and the spurs seen in many grand design galaxies, even with stellar feedback. The presence of the spiral potential does not have an explicit effect on the star formation rate, but can increase the star formation rate indirectly by enabling the formation of long‐lived, strongly bound clouds.

SHORT GMC LIFETIMES: AN OBSERVATIONAL ESTIMATE WITH THE PdBI ARCSECOND WHIRLPOOL SURVEY (PAWS)

“…By contrast, feedback, which can disrupt clouds as well as sweep up and compress interstellar gas (e.g., Dawson et al 2013), is expected to be spatially localized and coincident with tracers of highmass star formation. In this case, mass loss may be less gentle and potentially involve cloud splitting (Dobbs et al 2011), thus forming new clouds. At the same time, feedback acting externally can produce converging flows, possibly merging pre-existing cloud fragments (Dobbs et al 2012) and increasing cloud masses.…”

Structure distribution and turbulence in self-consistently supernova-driven ISM of multiphase magnetized galactic discs

“…Because of the wide diversity of spatial and temporal scales, which govern these cycles, it is not possible to directly simulate a galaxy (e.g. Tasker & Bryan 2006;Dubois & Teyssier 2008;Bournaud et al 2010;Kim et al 2011;Dobbs et al 2011;Tasker 2011;Hopkins et al 2011;Renaud et al 2013), with a well-resolved interstellar medium (ISM) although the spatial resolution is continuously improving. To address this question, an alternative approach has been developed which consists of simulating a small portion of a galactic disc leading to a better spatial resolution (Korpi et al 1999;Slyz et al 2005;de Avillez & Breitschwerdt 2005;Joung & Mac Low 2006;Hill et al 2012;Kim et al 2011Kim et al , 2013Gent et al 2013;Hennebelle & Iffrig 2014;Gatto et al 2015) although at the expense of solving the large galactic scales.…”

Influence of baryonic physics in galaxy simulations:

“…The galaxy models are often not self-consistent with no transfer of angular momentum from gas to stars or dark matter halo. (Slyz et al 2005;Tasker & Bryan 2006Dobbs & Bonnell 2008;Dobbs et al 2011;Shetty & Ostriker 2008;Wada et al 2011). …”