Baryons and Their Halos

TL;DR

This paper reviews the relationship between baryonic matter and dark matter halos in galaxies, highlighting the missing baryons problem and the correlation between galaxy dynamics and baryonic surface density.

Contribution

It provides a concise overview of two key aspects of baryon-halo connection, emphasizing systematic baryon deficits and the link between acceleration and baryonic density.

Findings

Baryon content in galaxies is less than the cosmic average, varying with galaxy mass.

Strong correlation exists between galaxy acceleration and baryonic surface density.

Abstract

Galaxies are composed of baryonic stars and gas embedded in dark matter halos. Here I briefly review two aspects of the connection between baryons and their halos. (1) The observed baryon content of galaxies falls short of the cosmic baryon fraction by an amount that varies systematically with mass. Where these missing baryons now reside is unclear. (2) The characteristic acceleration in disk galaxies correlates strongly with their baryonic mass surface density. This implies a close coupling between the gravitational dynamics, which is presumably dominated by dark matter, and the purely baryonic components of galaxies.