The Circumgalactic Medium of Milky Way-like Galaxies in the TNG50 Simulation -- I: Halo Gas Properties and the Role of SMBH Feedback by Rahul Ramesh et al. on Wednesday 30 November

We analyze the physical properties of gas in the circumgalactic medium (CGM)

of 132 Milky Way (MW)-like galaxies at $z=0$ from the cosmological

magneto-hydrodynamical simulation TNG50, part of the IllustrisTNG project. The

properties and abundance of CGM gas across the sample are diverse, and the

fractional budgets of different phases (cold, warm, and hot), as well as

neutral HI mass and metal mass, vary considerably. Over our stellar mass range

of $10^{10.5} < M_\star / \rm{M}_\odot < 10^{10.9}$, radial profiles of gas

physical properties from $0.15 < R\rm{ / R_{\rm 200c}} < 1.0$ reveal great CGM

structural complexity, with significant variations both at fixed distance

around individual galaxies, and across different galaxies. CGM gas is

multi-phase: the distributions of density, temperature and entropy are all

multimodal, while metallicity and thermal pressure distributions are unimodal;

all are broad. We present predictions for magnetic fields in MW-like halos: a

median field strength of $|B|\sim\,1\mu$G in the inner halo decreases rapidly

at larger distance, while magnetic pressure dominates over thermal pressure

only within $\sim0.2 \times \rm{R_{200c}}$. Virial temperature gas at $\sim

10^6\,$K coexists with a sub-dominant cool, $< 10^5\,$K component in

approximate pressure equilibrium. Finally, the physical properties of the CGM

are tightly connected to the galactic star formation rate, in turn dependent on

feedback from supermassive black holes (SMBHs). In TNG50, we find that energy

from SMBH-driven kinetic winds generates high-velocity outflows ($\gtrsim

500-2000$ km/s), heats gas to super-virial temperatures ($> 10^{6.5-7}$ K), and

regulates the net balance of inflows versus outflows in otherwise quasi-static

gaseous halos.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.00020v2