Speaker
Description
The origin and survival of the cold phase in the multiphase circumgalactic medium (CGM) remain central questions in galaxy evolution. In this talk, I will highlight the contribution of satellite galaxies to the cold gas budget of the Milky Way (MW)-like host galaxies. I will present results from our controlled experiments using high-resolution, idealized simulations with FIRE-2 physics of three different satellite mass distributions (10^8, 10^9, and 10^10 solar mass) and identify several mechanisms by which satellites can add cold gas to the CGM.
I will show that the satellite galaxies play a crucial role in replenishing the host CGM with cold gas through both direct ram-pressure stripping and induced cooling in the turbulent mixing layer of this stripped cold gas. These two mechanisms contribute a comparable amount of cold gas to the host CGM. All of the cold gas from low-mass satellites (<=10^9 solar mass) is rapidly lost within a Gyr as their stripped cold clouds mix with the hot CGM gas and get heated up quickly. On the other hand, massive satellites like the Large Magellanic Cloud (LMC) (~10^10 solar mass) provide a sustained cold gas supply over several Gyr due to their longer cloud-crushing time.
Additionally, I will highlight the role of cosmic rays (CRs) in shaping the evolution of this ram-pressure-stripped cold gas from satellites. By injecting CRs into the host CGM from supernovae of both the host and satellite galaxies, I find that CR enhances the surface area of the stripped clouds by providing additional pressure support, thereby boosting cooling in the turbulent mixing layer. As a result, CRs significantly impact the survival of cold-stripped gas and increase the cold-phase covering fraction in the host CGM, even for low-mass satellites. I will also show how changes in the content and transport mechanisms (such as the amount of diffusion, and magnetic field) of CRs in the CGM can significantly change the effect of CRs on this stripped cold gas.
These findings reveal that satellite galaxies serve as a key channel for supplying cold gas to the outer CGM of MW-like hosts and underscore the potential impact of CR physics on the survival of this cold phase in the CGM.