VLA Imaging of HI-bearing Ultra-Diffuse Galaxies from the ALFALFA Survey

TL;DR

This study presents high-resolution VLA and optical observations of 12 HI-bearing ultra-diffuse galaxies, revealing their gas distribution, rotation, and HI-stellar misalignments, providing insights into their structure and scaling relations.

Contribution

It provides the first resolved HI imaging and optical data for a sample of ultra-diffuse galaxies, highlighting their gas dynamics and spatial properties.

Findings

HI extends beyond stellar components.

HI disks often misaligned with stars.

HUDs follow the HI mass-diameter relation.

Abstract

Ultra-diffuse galaxies have generated significant interest due to their large optical extents and low optical surface brightnesses, which challenge galaxy formation models. Here we present resolved synthesis observations of 12 HI-bearing ultra-diffuse galaxies (HUDs) from the Karl G. Jansky Very Large Array (VLA), as well as deep optical imaging from the WIYN 3.5-meter telescope at Kitt Peak National Observatory. We present the data processing and images, including total intensity HI maps and HI velocity fields. The HUDs show ordered gas distributions and evidence of rotation, important prerequisites for the detailed kinematic models in Mancera Pi\~na et al. (2019b). We compare the HI and stellar alignment and extent, and find the HI extends beyond the already extended stellar component and that the HI disk is often misaligned with respect to the stellar one, emphasizing the importance of caution when approaching inclination measurements for these extreme sources. We explore the HI mass-diameter scaling relation, and find that although the HUDs have diffuse stellar populations, they fall along the relation, with typical global HI surface densities. This resolved sample forms an important basis for more detailed study of the HI distribution in this extreme extragalactic population.