Synthetic absorption-line comparison of simulated and observed Milky Way CGM clouds

Construct a fair comparison between the simulated Milky Way circumgalactic medium and intermediate- and high-velocity cloud observations by identifying discrete cloud-like structures in the simulations and generating synthetic absorption-line measurements.

Background

The simulations compare mass-weighted median gas-metallicity profiles with observations of individual intermediate- and high-velocity clouds and with a local constraint from the eROSITA bubbles. The authors emphasize that these observables do not trace identical quantities: the observed cloud metallicities are derived along selected sightlines, whereas the simulations average over all halo gas at a given height, and the eROSITA measurement probes transient shocked gas.

A resolved, observation-like comparison therefore remains to be performed. It would require isolating discrete cloud-like structures in the simulated circumgalactic medium and producing synthetic absorption-line measurements that can be analyzed in the same manner as the observations.

References

Therefore, a fair comparison would require identifying discrete cloud-like structures in our simulations and generating synthetic absorption-line measurements, which we defer to future work.

— Same galaxy, different CGM: how the metal loading of galactic winds regulates the baryon cycle in Milky Way-mass galaxies  (2609.03083 - Khatri et al., 2 Sep 2026) in Section 4.2, “Comparison with observations”