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The Complexity of CGM gas in Simulated Milky Way-like Halos

Exploring the diversity and complexity of CGM gas properties using a sample of galaxies from the TNG50 simulation

Published onNov 23, 2022
The Complexity of CGM gas in Simulated Milky Way-like Halos

A four-prong view of the CGM around a simulated galaxy like the Milky Way

This figure is from a study (Ramesh et al. 2022 [1]) of gas in the circumgalactic medium (CGM) of a sample of 132 Milky Way-like galaxies from the cosmological magneto-hydrodynamical simulation TNG50, part of the IllustrisTNG project.

The figure shows four important physical properties of halo gas surrounding one of these 132 galaxies. The CGM, which we define as the region between the inner circle (radius equal to 15% the halo virial radius) and outer circle (radius equal to the halo virial radius), is visibly complex. While most of the CGM gas is rarified, we observe ‘clouds’ of gas that are much more dense (top-left quadrant; Gas Column Density). These dense gas clouds are typically cold, and co-exist with hot gas at or near the halo virial temperature (top-right quadrant; Gas Temperature). As a result of the high virial temperature, a large fraction of the volume is filled by gas at high entropy, with small overdensities at lower values of entropy embedded within (lower-right quadrant; Gas Entropy). A radial gradient in thermal pressure is present, with the inner halo dominated by high thermal pressure, and the outer halo by low thermal pressure (lower-left quadrant; Gas Thermal Pressure).

Although this example is typical, significant variation across the sample is evident, as can be seen in our infinite gallery. This diversity is a combined result of many factors, with feedback energy injected by the central supermassive black hole (SMBH) being one of them: in TNG50, kinetic winds driven by the SMBH heat gas to super-virial temperatures, generate high-velocity outflows, and regulate the net balance of inflows versus outflows in otherwise quasi-static halos.

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