Pegasus V/Andromeda XXXIV-a newly discovered ultrafaint dwarf galaxy on the outskirts of Andromeda

DOI: 
10.1093/mnrasl/slac063
Publication date: 
08/09/2022
Main author: 
Collins, Michelle L. M.
IAA authors: 
Martínez-Delgado, David
Authors: 
Collins, Michelle L. M.;Charles, Emily J. E.;Martínez-Delgado, David;Monelli, Matteo;Karim, Noushin;Donatiello, Giuseppe;Tollerud, Erik J.;Boschin, Walter
Journal: 
Monthly Notices of the Royal Astronomical Society
Refereed: 
Yes
Publication type: 
Article
Volume: 
515
Pages: 
L72-L77
Abstract: 
We report the discovery of an ultrafaint dwarf in the constellation of Pegasus. Pegasus V (Peg V)/Andromeda XXXIV 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 overdensity 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<SUB>V</SUB> = -6.3 ± 0.2 and a half-light radius of r<SUB>half</SUB> = 89 ± 41 pc. It is located ~260 kpc from Andromeda in the outskirts of its halo. The RGB is well fitted 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 reionization fossil. This is the first detection of an ultrafaint dwarf outside the deep Pan-Andromeda Archaeological Survey area, and points to a rich, faint satellite population in the outskirts of our nearest neighbour.
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2022MNRAS.515L..72C/abstract
ADS Bibcode: 
2022MNRAS.515L..72C
Keywords: 
galaxies: dwarf;galaxies: individual;Astrophysics - Astrophysics of Galaxies;Astrophysics - Cosmology and Nongalactic Astrophysics