CMB as a possible new tool to study the dark baryons in galaxies

TL;DR

This paper proposes using Cosmic Microwave Background (CMB) data from WMAP to detect and study hidden baryons in galactic halos, specifically demonstrating a temperature asymmetry in M31's halo that could reveal the presence of dark baryons.

Contribution

It introduces a novel method of using CMB measurements to detect galactic halo baryons, providing potential new insights into the missing baryon problem.

Findings

Detected a temperature asymmetry in M31's halo up to 120 kpc

First microwave detection of a galactic halo

Suggests CMB data can probe hidden baryons in galaxies

Abstract

Baryons constitute about 4% of our universe, but most of them are missing and we do not know where and in what form they are hidden. This constitute the so-called missing baryon problem. A possibility is that part of these baryons are hidden in galactic halos. We show how the 7-year data obtained by the WMAP satellite may be used to trace the halo of the nearby giant spiral galaxy M31. We detect a temperature asymmetry in the M31 halo along the rotation direction up to about 120 kpc. This could be the first detection of a galactic halo in microwaves and may open a new way to probe hidden baryons in these relatively less studied galactic objects using high accuracy CMB measurements.