Missing Mass in Collisional Debris from Galaxies

TL;DR

This study investigates the mass composition of recycled dwarf galaxies formed from galactic debris, revealing they contain significant unseen mass likely due to cold molecular gas, challenging previous assumptions.

Contribution

The paper provides observational evidence that recycled dwarf galaxies contain substantial dark or unseen mass, suggesting the presence of cold molecular gas in their disks.

Findings

Recycled dwarf galaxies have about twice the visible matter in mass.

The unseen mass is likely cold molecular gas, not dark matter.

This mass accounts for a significant part of missing baryons.

Abstract

Recycled dwarf galaxies can form in the collisional debris of massive galaxies. Theoretical models predict that, contrary to classical galaxies, they should be free of non-baryonic Dark Matter. Analyzing the observed gas kinematics of such recycled galaxies with the help of a numerical model, we demonstrate that they do contain a massive dark component amounting to about twice the visible matter. Staying within the standard cosmological framework, this result most likely indicates the presence of large amounts of unseen, presumably cold, molecular gas. This additional mass should be present in the disks of their progenitor spiral galaxies, accounting for a significant part of the so-called missing baryons.