First Results from SMAUG: Uncovering the Origin of the Multiphase Circumgalactic Medium with a Comparative Analysis of Idealized and Cosmological Simulations

Abstract

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 TNG100 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 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 ( ) when strong galactic feedback models are employed, but the outer CGM ( ) 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.

Characterizing mass, momentum, energy, and metal outflow rates of multiphase galactic winds in the FIRE-2 cosmological simulations

“…While we do not know whether the identity of the gas leaving the virial shell is the same as the gas that was previously ejected from the ISM (e.g., much of the ISM outflows could have stalled in the CGM while still pushing ambient halo gas outwards), our finding that 𝜂 halo /𝜂 ISM ∼ 1 in the low-redshift MW halos combined with their relatively large Bernoulli velocities of hot outflows in Figure 13 suggests that outflows can have substantial effects in MW halos (see also our supplementary movies, e.g., Figure 1). This agrees with the conclusions drawn from the comparative CGM analysis of diverse simulations by Fielding et al (2020b). For dwarfs, the halo mass loading is generally many times higher than the ISM mass loading expected to make it to 2𝑅 vir .…”

Inflow of low-metallicity cool gas in the halo of the Andromeda galaxy

“…As mentioned in Section 4.1, this in line with the findings of AFP21, where we obtained a similar result for a sample of about 40 nearby starforming galaxies selected from the COS-Halos and COS-GASS samples (Werk et al 2012;Borthakur et al 2015). These results are also consistent with what found by Fielding et al (2020) in idealized hydrodynamical simulations, where feedback from the central galaxy is not able to bring cool gas in the outer CGM. Galactic outflows could however have some role in the production of cold gas in the inner parts of the halo, a few kpc above the disc (e.g.…”

Cosmological Simulations of Quasar Fueling to Subparsec Scales Using Lagrangian Hyper-refinement

“…This work has been developed with the support of the Simulating Multiscale Astrophysics to Understand Galaxies (SMAUG) consortium, 13 which attempts to reduce the uncertainties associated with subgrid parameterizations of key baryonic processes in galaxy formation in order to improve the accuracy of fundamental cosmological measurements. Other work in SMAUG has centered on star formation and stellar feedback (Li et al 2010(Li et al , 2020Kim et al 2020;Motwani et al 2020), the physics of the CGM (Fielding et al 2020), and the connection between semi-analytic models and cosmological hydrodynamic simulations (Pandya et al 2020). Our work complements these by providing a key step toward developing better subgrid models for black hole accretion in galaxy formation, which play a key role in the evolution of massive galaxies and large-scale structure.…”