Ultra diffuse galaxies in the Hydra I cluster from the LEWIS Project: Phase-Space distribution and globular cluster richness

TL;DR

This study investigates ultra diffuse galaxies in the Hydra I cluster, revealing their early infall into the cluster and challenging the idea that globular cluster richness correlates with infall time, suggesting alternative quenching mechanisms.

Contribution

It provides new radial velocity measurements for Hydra I UDGs and analyzes their phase-space distribution, offering insights into their infall history and globular cluster properties.

Findings

UDGs are consistent with early infall into Hydra I cluster.

No correlation found between GC richness and infall time.

Alternative quenching mechanisms are suggested.

Abstract

Although ultra diffuse galaxies (UDGs) are found in large numbers in clusters of galaxies, the role of the cluster environment in shaping their low surface brightness and large sizes is still uncertain. Here we examine a sample of UDGs in the Hydra I cluster (D = 51 Mpc) with new radial velocities obtained as part of the LEWIS (Looking into the faintest with MUSE) project using VLT/MUSE data. Using a phase-space, or infall diagnostic, diagram we compare the UDGs to other known galaxies in the Hydra I cluster and to UDGs in other clusters. The UDGs, along with the bulk of regular Hydra I galaxies, have low relative velocities and are located near the cluster core, and thus consistent with very early infall into the cluster. Combining with literature data, we do not find the expected trend of GC-rich UDGs associated with earlier infall times. This result suggests that quenching mechanisms other than cluster infall should be further considered, e.g. quenching by strong feedback or in cosmic sheets and filaments. Tidal stripping of GCs in the cluster environment also warrants further modelling.