The Resolved Sunyaev–Zel’dovich Profiles of Nearby Galaxy Groups

Abstract

Abstract Many of the baryons in galaxy groups are thought to have been driven out to large distances (≳R 500) by feedback, but there are few constraining observations of this extended gas. This work presents the resolved Sunyaev–Zel’dovich (SZ) profiles for a stacked sample of 10 nearby galaxy groups within the mass range log 10 ( M 500 [ M ⊙ ] ) = 13.6 – 13.9 . We measured the SZ profiles using the publicly available y-map from the Planck Collaboration as well as our own y-maps constructed from more recent versions of Planck data. The y-map extracted from the latest data release yielded a significant SZ detection out to 3 R 500. In addition, the stacked profile from these data was consistent with simulations that included AGN feedback. Our best-fit model using the latest Planck data suggested a baryon fraction ≈5.6% within R 500. This is significantly lower than the cosmic value of ≈16%, supporting the idea that baryons have been driven to large radii by AGN feedback. Lastly, we discovered a significant (∼3σ) “bump” feature near ∼2 R 500 that is most likely the signature of internal accretion shocks.