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24th of October 2023
WALLABY observations of Ultra-Diffuse Galaxies
by For et al.
Low-surface-brightness (LSB) galaxies have been known for decades, and with the advancement of optical imaging instruments and search techniques, a large population of extreme LSB galaxies has recently been uncovered. The discovery of tens to hundreds of spatially-extended extreme LSB galaxies -- Ultra Diffuse Galaxies (UDGs) -- has reinvigorated the interest in studying these objects. UDGs are prevalent across all environments: in clusters, galaxy groups and in the field. As they represent an extreme end of the LSB dwarf population, they are important in testing galaxy formation models.

For et al. present a pilot study of the atomic neutral hydrogen gas (HI) content of ultra-diffuse galaxy (UDG) candidates using an ASKAP WALLABY data set. Only one HI detection is found, which they classify as a low-surface-brightness dwarf, with six putative UDGs found to be HI-free. One putative UDG, SMDG 0345097−223826, appears to be located at the tail end of a stellar stream of 6dFGS J034506.0−223632. There is also a fairly blue spiral galaxy, LEDA 811216, that is located south of 6dFGS J034506.0−223632 and alongside the stellar stream. The location of LEDA 811216 could be a projection effect or it could in fact be interacting with 6dFGS J034506.0−22363. The slight disruption on the optical morphology of LEDA 811216 suggests that this pair is interacting, however, no HI was found at their locations. The location at the tail end of a stellar stream suggests SMDG 0345097−223826 may have been formed via tidal heating/interaction.

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