Paper detail

Testing galaxy feedback models with the first resolved profiles of the 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 (AGNs) 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 (eFEDS), 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 ISM, producing accurate radial profiles. We compare the profiles to mock X-ray observations of galaxy stacks in the IllustrisTNG100 (TNG) and EAGLE cosmological simulations. We detect extended emission from both the high-mass ($10.7<\log(M_*/M_\odot)<11.2$) and low-mass ($10.2<\log(M_*/M_\odot)<10.7$) galaxy stacks. Galaxies have somewhat more luminous CGM between $10-100$~kpc if they are more massive or star-forming. However, the luminosity increases slower with stellar mass than predicted in simulations. Simulated quenched galaxies are far 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 under-efficient stellar feedback models. Our results highlight the need to modify future prescriptions of galaxy feedback models.