Testing Galaxy Feedback Models with Resolved X-Ray Profiles of the Hot Circumgalactic Medium

The hot (>10(6) K) phase of the circumgalactic medium (CGM) contains a large fraction of baryons in galaxies. It also retains signatures of the processes that shaped the galaxies, such as feedback from active galactic nuclei and supernovae, and offers a uniquely powerful way to constrain theoretical models of feedback. It is, however, notoriously difficult to detect. By stacking 2643 optically selected galaxies in the eROSITA Final Equatorial Depth Survey, we present spatially resolved properties of the extended CGM in both star-forming and quiescent galaxies spanning an order of magnitude in stellar mass. We mask out resolved point sources and galaxy groups/clusters and model the contribution from X-ray binaries and the hot interstellar medium, producing accurate radial profiles. We compare the profiles to mock X-ray observations of galaxy stacks in the IllustrisTNG100 and EAGLE cosmological simulations. We detect extended emission from both the high-mass (10.7 < log(M-*/M-circle dot) < 11.2) and low-mass (10.2 < log(M-*/M-circle dot) < 10.7) galaxy stacks. Galaxies have somewhat more luminous CGM between 10 and 100 kpc if they are more massive or star-forming. However, the luminosity increases more slowly with stellar mass than predicted in simulations. Simulated quenched galaxies are dimmer than observed, suggesting that they rely too heavily on CGM ejection for quenching. Star-forming galaxies are observed to have flatter and more extended profiles than in simulations, suggesting underefficient stellar feedback models. Our results highlight the need to modify future prescriptions of galaxy feedback models. Unified Astronomy Thesaurus concepts: Circumgalactic medium (1879); Galaxy processes (614); Galaxy physics (612); Galaxy evolution (594)

Automated summary

By stacking observations of a large number of galaxies, scientists were able to study the properties of the extended circumgalactic medium (CGM) in both star-forming and quiescent galaxies and compare them with simulations. They found that the mass and star formation activity of galaxies affect the brightness of their extended CGM, but the observed brightness increases more slowly with stellar mass than predicted in simulations. Quiescent galaxies are dimmer than expected, suggesting they rely too heavily on CGM ejection to quench star formation. Star-forming galaxies have flatter and more extended profiles than simulated, indicating inefficient stellar feedback models.