C. T. Pratt | Searcharxiv

arXiv2021

The Resolved Sunyaev--Zel'dovich Profiles of Nearby Galaxy Groups

Much of the baryons in galaxy groups are thought to have been driven out to large distances ($\gtrsim$$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_{\odot}]) = 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 were consistent with simulations that included AGN feedback. Our best-fit model using the latest $Planck$ data suggested a baryon fraction $\approx 5.6\%$ within $R_{500}$. This is significantly lower than the cosmic value of $\approx 16\%$, supporting the idea that baryons have been driven to large radii by AGN feedback. Lastly, we discovered a significant ($\sim 3σ$) "bump" feature near $\sim 2$ $R_{500}$ that is most likely the signature of internal accretion shocks.

astro-ph.CO↗

arXiv2018

The Spread of Metals into the Low-Redshift Intergalactic Medium

We investigate the association between galaxies and metal-enriched and metal-deficient absorbers in the local universe ($z < 0.16$) using a large compilation of FUV spectra of bright AGN targets observed with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope. In this homogeneous sample of 18 O VI detections at $N_{\rm O\,{VI}}\geq13.5~\mathrm{cm}^{-2}$ and 18 non-detections at $N_{\rm O\,{VI}}<13.5~\mathrm{cm}^{-2}$ using Lya absorbers with ${N_{\rm H\,{I}}\geq} 10^{14}~\mathrm{cm}^{-2}$, the maximum distance O VI extends from galaxies of various luminosities is $\sim0.6$ Mpc, or $\sim5$ virial radii, confirming and refining earlier results. This is an important value that must be matched by numerical simulations, which input the strength of galactic winds at the sub-grid level. We present evidence that the primary contributors to the spread of metals into the circum- and intergalactic media are sub-$L^*$ galaxies ($0.25L^*<L<L^*$). The maximum distances that metals are transported from these galaxies is comparable to, or less than, the size of a group of galaxies. These results suggest that, where groups are present, the metals produced by the group galaxies do not leave the group. Since many O VI non-detections in our sample occur at comparably close impact parameters as the metal-bearing absorbers, some more pristine intergalactic material appears to be accreting onto groups where it can mix with metal-bearing clouds.

astro-ph.GA↗