2026/02/20 by T. R. Adams, Tim R. Adams, Brendon J. Brewer +3 · 2 voices · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.33232/001c.158197
openalex publication_date 2026/02/23 · openalex created_date 2026/02/24 · openalex updated_date 2026/07/28
We investigate the kinematics of the potential ultra-faint dwarf galaxy (UFD) UMa III/U1 using Bayesian inference to search for the signal of any potential intrinsic rotation. The magnitude of rotation is relevant to estimating the total mass of UMa III/U1 which is critical in determining whether or not UMa III/U1 is in fact a UFD, or possibly a star cluster home to a significant binary fraction. A non-rotating model and a rotational model are fitted for the current total population of member stars of UMa III/U1 finding that a non-rotating model was preferred by a factor of ∼5−12×. This was repeated on a reduced population of UMa III/U1 where potential contaminant stars were removed. A similar preference for non-rotation was found for these reduced populations. We calculate a lower-bound rotational mass estimate for UMa III/U1 and a corresponding lower bound mass-to-light ratio of 734.4 for the total population. We conclude that UMa III/U1 still remains an ambiguous object with viable arguments for both the UFD and self-gravitating star cluster scenarios, however under both, UMa III/U1 is unlikely to be supported by rotational pressure.