Efficacy of early stellar feedback in low gas surface density environments

Abstract

We present a suite of high-resolution radiation hydrodynamic simulations of a small patch (1 kpc2) of the interstellar medium (ISM) performed with AREPO-RT, with the aim to quantify the efficacy of various feedback processes like supernova (SN) explosions, photoheating, and radiation pressure in low gas surface density galaxies (Σgas ∼ 10M⊙pc-2). We show that radiative feedback decrease the star formation rate and therefore the total stellar mass formed by a factor of approximately two. This increases the gas depletion time-scale and brings the simulated Kennicutt-Schmidt relation closer to the observational estimates. Radiation feedback coupled with SN is more efficient at driving outflows with the mass and energy loading increasing by a factor of ∼10. This increase is mainly driven by the additional entrainment of medium-density (10-2 cm -3 ≤ n < 1cm-3) warm (300 K < T ≤ 8000 K) material. Therefore, including radiative feedback tends to launch colder, denser, and more mass- and energy-loaded outflows. This is because photoheating of the high-density gas around a newly formed star overpressurizes the region, causing it to expand. This reduces the ambient density in which the SN explode by a factor of 10-100 which in turn increases their momentum output by a factor of ∼1.5-2.5. Finally, we note that in these low gas surface density environments, radiative feedback primarily impact the ISM via photoheating and radiation pressure has only a minimal role in regulating star formation.