Home Galactic Efficacy of early stellar feedback in low gas surface density environments. (arXiv:1812.01614v1...

Efficacy of early stellar feedback in low gas surface density environments. (arXiv:1812.01614v1 [astro-ph.GA])

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Authors: Rahul Kannan (Harvard/CfA), Federico Marinacci (Harvard/CfA), Christine M. Simpson (U Chicago), Simon C. O. Glover (ITA Heidelberg), Lars Hernquist (Harvard/CfA)

We present a suite of high resolution radiation hydrodynamic simulations of a
small patch ($1 {rm kpc}^2$) of the inter-stellar medium (ISM) performed
with Arepo-RT, with the aim to quantify the efficacy of various feedback
processes like supernovae explosions (SNe), photoheating and radiation pressure
in low gas surface density galaxies ($Sigma_{rm gas} simeq 10 {rm
M}_odot {rm pc}^{-2}$). We show that radiation fields decrease the star
formation rate and therefore the total stellar mass formed by a factor of $sim
2$. This increases the gas depletion timescale and brings the simulated
Kennicutt-Schmidt relation closer to the observational estimates. Radiation
feedback coupled with SNe is more efficient at driving outflows with the mass
and energy loading increasing by a factor of $sim 10$. This increase is mainly
driven by the additional entrainment of medium density ($10^{-2} leq n< 1
{rm cm}^{-3}$), warm ($300 {rm K}leq T<8000 {rm K}$) material.
Therefore including radiation fields tends to launch colder, denser and higher
mass and energy loaded outflows. This is because photoheating of the high
density gas around a newly formed star over-pressurises the region, causing it
to expand. This reduces the ambient density in which the SNe explode by a
factor of $10-100$ which in turn increases their momentum output by a factor of
$sim 1.5-2.5$. Finally, we note that in these low gas surface density
environments, radiation fields primarily impact the ISM via photoheating and
radiation pressure has only a minimal role in regulating star formation.

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