Conditions for supernovae driven galactic winds

TL;DR

This paper challenges the traditional view that supernovae heating alone drives galactic winds, proposing instead that correlated supernovae in dense molecular regions are necessary for powerful outflows.

Contribution

It demonstrates that supernovae heating cannot easily produce large hot gas filling factors, and identifies conditions under which correlated supernovae can drive galactic winds.

Findings

Large hot gas filling factors are difficult to achieve via SNe heating.

Correlated supernovae in molecular clouds can drive galactic outflows.

Outflows are effective if molecular surface density exceeds 10^3 M_sun/pc^2.

Abstract

We point out that the commonly assumed condition for galactic outflows, that supernovae (SNe) heating is efficient in the central regions of starburst galaxies, suffers from invalid assumptions. We show that a large filling factor of hot ($\ge 10^6$ K) gas is difficult to achieve through SNe heating, irrespective of the initial gas temperature and density, and of its being uniform or clumpy. We instead suggest that correlated supernovae from OB associations in molecular clouds in the central region can drive powerful outflows if the molecular surface density is $> 10^3$ M$_{\odot}$ pc$^{-2}$.