Seeding the CGM: How Satellites Populate the Cold Phase of Milky Way Halos

TL;DR

This study explores how satellite galaxies contribute to the cold gas in the circumgalactic medium of Milky Way-like galaxies, highlighting mechanisms like ram pressure stripping and cooling, with satellite mass influencing gas retention.

Contribution

It provides new insights into the mechanisms and satellite mass dependence of cold gas transfer to the CGM, including the effects of stellar feedback.

Findings

Less massive satellites lose cold gas quickly (~0.5-1 Gyr).

Stellar feedback accelerates cold cloud destruction.

More massive satellites can supply cold gas for several Gyrs.

Abstract

The origin of the cold phase in the CGM is a highly debated question. We investigate the contribution of satellite galaxies to the cold gas budget in the circumgalactic medium (CGM)of a Milky Way-like host galaxy. We perform controlled experiments with three different satellite mass distributions and identify several mechanisms by which satellites can add cold gas to the CGM, including ram pressure stripping and induced cooling in the mixing layer of the stripped cold gas. These two mechanisms contribute a comparable amount of cold gas to the host CGM. We find that the less massive satellites ($\leq 10^9 M_\odot$) not only lose all of their cold gas in a short period ($\sim$ 0.5-1 Gyr), but their stripped cold clouds also mix with the hot CGM gas and get heated up quickly. However, stellar feedback from these less massive satellites can hugely alter the fate of their stripped gas. Feedback speeds up the destruction of the stripped cold clouds from these satellites by making them more diffuse with more surface area. On the other hand, the more massive satellites (LMC or SMC-like $\sim 10^{10} M_\odot$) can add cold gas to the total gas budget of the host CGM for several Gyrs.