Feedback Regulated Star Formation: From Star Clusters to Galaxies

TL;DR

This paper presents a semi-analytical model of star formation regulated by stellar feedback, showing how metallicity influences star formation efficiency and reproducing observed star formation laws across different regimes.

Contribution

It introduces a metallicity-dependent feedback model that links stellar winds to star formation efficiency and surface density relations, extending understanding of star formation regulation.

Findings

Higher metallicity leads to stronger stellar winds and faster gas expulsion.

The model reproduces observed star formation laws from low to high gas surface densities.

Metallicity influences star formation rate surface density across all regimes.

Abstract

This paper summarises results from semi-analytical modelling of star formation in protocluster clumps of different metallicities. In this model, gravitationally bound cores form uniformly in the clump following a prescribed core formation efficiency per unit time. After a contraction timescale which is equal to a few times their free-fall times, the cores collapse into stars and populate the IMF. Feedback from the newly formed OB stars is taken into account in the form of stellar winds. When the ratio of the effective wind energy of the winds to the gravitational energy of the system reaches unity, gas is removed from the clump and core and star formation are quenched. The power of the radiation driven winds has a strong dependence on metallicity and increases with increasing metallicity. Thus, winds from stars in the high metallicity models lead to a rapid evacuation of the gas from the protocluster clump and to a reduced star formation efficiency, SFE_{exp}, as compared to their low metallicity counterparts. By combining SFE_{exp} with the timescales on which gas expulsion occurs, we derive the metallicity dependent star formation rate per unit time in this model as a function of the gas surface density Sigma_{g}. This is combined with the molecular gas fraction in order to derive the dependence of the surface density of star formation Sigma_{SFR} on Sigma_{g}. This feedback regulated model of star formation reproduces very well the observed star formation laws extending from low gas surface densities up to the starburst regime. Furthermore, the results show a dependence of Sigma_{SFR} on metallicity over the entire range of gas surface densities, and can also explain part of the scatter in the observations.