Constraints on the missing baryons from the kinetic Sunyaev-Zeldovich effect in Planck data

TL;DR

This study uses Planck data to estimate the amount of missing baryons around central galaxies, finding that regions near these galaxies contain about half of the universe's baryons at that epoch, consistent with baryons following dark matter.

Contribution

First measurement of the missing baryons around central galaxies using the kinetic Sunyaev-Zeldovich effect in Planck data.

Findings

Regions around central galaxies contain roughly half of the universe's baryons.

Measured optical depths are consistent with all baryons being inside and around these galaxies.

Results support the hypothesis that baryons follow dark matter distribution.

Abstract

We estimate the amount of the {\it missing baryons} detected by the \Planck\ measurements of the cosmic microwave background in the direction of Central Galaxies (CGs) identified in the Sloan galaxy survey. The peculiar motion of the gas inside and around the CGs unveils values of the Thomson optical depth $\tau_{\rm T}$ in the range $0.2$--$2\times 10^{-4}$, indicating that the regions probed around CGs contain roughly half of the total amount of baryons in the Universe at the epoch where the CGs are found. If baryons follow dark matter, the measured $\tau_{\rm T}$s are compatible with the detection all the baryons existing inside and around the CGs.