http://arxiv.org/abs/2204.09068
We report the discovery of an ultra-faint dwarf in the constellation of Pegasus. Pegasus~V (Peg~V) was initially identified in the public imaging data release of the DESI Legacy Imaging Surveys and confirmed with deep imaging from Gemini/GMOS-N. The colour-magnitude diagram shows a sparse red giant branch (RGB) population and a strong over-density of blue horizontal branch stars. We measure a distance to Peg~V of $D=692^{+33}{-31}$~kpc, making it a distant satellite of Andromeda with $M_V=-6.3\pm0.2$ and a half-light radius of $r{\rm half}=89\pm41$~pc. It is located $\sim260$~kpc from Andromeda in the outskirts of its halo. The RGB is well-fit by a metal-poor isochrone with [Fe/H]$=-3.2$, suggesting it is very metal poor. This, combined with its blue horizontal branch could imply that it is a reionisation fossil. This is the first detection of an ultra-faint dwarf outside the deep Pan-Andromeda Archaeological Survey area, and points to a rich, faint satellite population in the outskirts of our nearest neighbour.
M. Collins, E. Charles, D. Martínez-Delgado, et. al.
Thu, 21 Apr 22
37/73
Comments: Submitted to MNRAS Letters. 6 pages, 4 figures. Comments welcome
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