Radial velocities and stellar populations for a sample of MATLAS survey dwarfs

TL;DR

This study presents spectroscopic data for 12 dwarf galaxies from the MATLAS survey, confirming their velocities, revising some associations, and analyzing their stellar populations, revealing diverse ages and metallicities that challenge existing models.

Contribution

First spectroscopic analysis of MATLAS dwarfs providing revised galaxy associations and detailed stellar population insights.

Findings

Confirmed velocities for 9 dwarfs consistent with host galaxies.

Reclassified one galaxy from ultra-diffuse to dwarf galaxy in the field.

Found a mix of old, passive and star-forming galaxies with younger ages and higher metallicities.

Abstract

Spectroscopic observations are essential for confirming associations, measuring kinematics, and determining stellar populations in dwarf galaxies. Here, we present Keck Cosmic Web Imager (KCWI) spectra for 12 MATLAS survey dwarfs. For 9, we confirm recession velocities consistent with their literature-assumed host galaxies. We propose revisions of the host galaxy associations for MATLAS-631, 1494, and 1938. For MATLAS-1494, our measured redshift reclassifies it from an ultra-diffuse galaxy candidate to a dwarf galaxy that is of smaller physical size and places it in the field. It also appears old and passive, providing a challenge to models that invoke quenching by tidal effects. Additionally, we measure stellar population estimates for 7 of the 12 galaxies, finding a 'mixed bag' of old quenched galaxies and those that are currently forming stars. Compared to the literature we find generally younger ages and higher metallicities. This result may help reconcile the observed offset of MATLAS survey dwarf galaxies from the universal stellar mass-metallicity relationship reported by Heesters et al. (2023).