First results from SMAUG: Uncovering the Origin of the Multiphase
  Circumgalactic Medium with a Comparative Analysis of Idealized and
  Cosmological Simulations
  We examine the properties of the circumgalactic medium (CGM) at low redshift
in a range of simulated Milky Way mass halos. The sample is comprised of seven
idealized simulations, an adaptive mesh refinement cosmological zoom-in
simulation, and two groups of 50 halos with star forming or quiescent galaxies
taken from the IllustrisTNG100 simulation. The simulations have very different
setups, resolution, and feedback models, but are analyzed in a uniform manner.
By comparing median radial profiles and mass distributions of CGM properties,
we isolate key similarities and differences. In doing so, we advance the
efforts of the SMAUG (Simulating Multiscale Astrophysics to Understand
Galaxies) project that aims to understand the inherently multiscale galaxy
formation process. In the cosmological simulations, the CGM exhibits nearly
flat temperature distributions, and broad pressure and radial velocity
distributions. In the idealized simulations, similar distributions are found in
the inner CGM ($\lesssim 0.5 \, r_{\rm 200c}$) when strong galactic feedback
models are employed, but the outer CGM ($\gtrsim 0.5 \, r_{\rm 200c}$) has a
much less prominent cold phase, and narrower pressure and velocity
distributions even in models with strong feedback. This comparative analysis
demonstrates the dominant role feedback plays in shaping the inner CGM and the
increased importance of cosmological effects, such as nonspherical accretion
and satellite galaxies, in the outer CGM. Furthermore, our findings highlight
that while cosmological simulations are required to capture the multiphase
structure of the CGM at large radii, idealized simulations provide a robust
framework to study how galactic feedback interacts with the inner CGM and
thereby provide a reliable avenue to constrain feedback prescriptions.
