The Formation of Ultra Diffuse Galaxies in Cored Dark Matter Halos Through Tidal Stripping and Heating

TL;DR

This paper proposes that ultra-diffuse galaxies form through tidal stripping and heating of dwarf satellites in cored dark matter halos, explaining their observed properties and dependence on cluster environment.

Contribution

It introduces a semi-analytic model demonstrating that cored halo satellites can reproduce UDG characteristics, highlighting the role of tidal effects in their formation.

Findings

Cored halo satellites expand significantly under tidal forces.

The model matches observed UDG sizes and stellar masses.

Cored halos better explain UDG abundance in clusters.

Abstract

We propose that the Ultra-Diffuse Galaxy (UDG) population represents a set of satellite galaxies born in $\sim10^{10}-10^{11}$ M$_\odot$ halos, similar to field dwarfs, which suffer a dramatic reduction in surface brightness due to tidal stripping and heating. This scenario is observationally motivated by the radial alignment of UDGs in Coma as well as the significant dependence of UDG abundance on cluster mass. As a test of this formation scenario, we apply a semi-analytic model describing the change in stellar mass and half-light radius of dwarf satellites, occupying either cored or cuspy halos, to cluster subhalos in the Illustris-dark simulation. Key to this model are results from simulations which indicate that galaxies in cored dark-matter halos expand significantly in response to tidal stripping and heating, whereas galaxies in cuspy halos experience limited size evolution. Our analysis indicates that a population of tidally-stripped dwarf galaxies, residing in cored halos (like those hosting low-surface brightness field dwarfs), is able to reproduce the observed sizes and stellar masses of UDGs in clusters remarkably well.