Gas-rich, field ultra-diffuse galaxies host few globular clusters

Michael G. Jones, Ananthan Karunakaran, Paul Bennet, David J. Sand, Kristine Spekkens, Burcin Mutlu-Pakdil, Denija Crnojevic, Steven Janowiecki, Lukas Leisman, Catherine E. Fielder

Submitted on 1 November 2022


We present Hubble Space Telescope imaging of 14 gas-rich, low surface brightness and ultra-diffuse galaxies (UDGs) in the field at distances of 25-36 Mpc. An inspection of point-like sources brighter than the turnover magnitude of the globular cluster luminosity function and within twice the half-light radii of each galaxy reveals that, unlike those in denser environments, gas-rich, field UDGs host very few old globular clusters (GCs). Most of the targets (nine) have zero candidate GCs, with the remainder having one or two candidates each. These findings are broadly consistent with expectations for normal dwarf galaxies of similar stellar mass. This rules out gas-rich, field UDGs as potential progenitors of the GC-rich UDGs that are typically found in galaxy clusters. However, some in galaxy groups may be directly accreted from the field. In line with other recent results, this strongly suggests that there must be at least two distinct formation pathways for UDGs, and that this sub-population is simply an extreme low surface brightness extension of the underlying dwarf galaxy population. The root cause of their diffuse stellar distributions remains unclear, but the formation mechanism appears to only impact the distribution of stars (and potentially dark matter), without strongly impacting the distribution of neutral gas, the overall stellar mass, or the number of GCs.


Comment: Submitted to AAS journals

Subject: Astrophysics - Astrophysics of Galaxies