2025/07/17 by Borja Anguiano, Geraint F. Lewis, Anguiano, Borja +2
Physics and Astronomy · #Galaxies: Formation, Evolution, Phenomena #Astronomy and Astrophysical Research #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2507.13488
We report the discovery of a possible sub-population of stellar clusters that appear to follow retrograde orbits around the third largest galaxy in the Local Group, M33 (Triangulum). This spiral disk galaxy has apparently had a mostly quiescent existence, although recent discoveries, particularly of a pronounced warp in the gas and stellar disk, suggest that M33's relatively quiet past was interrupted at least once by a dynamical interaction with another galaxy. We suggest that this sub population provides evidence of accretion of one or more dwarf galaxies in M33's history. We estimate a lower limit for the accreted halo virial mass of M\rm vir ∼ (7 ± 3) × 1010\msun, accounting for about 10% of the virial mass in the halo of M33 that has an accretion origin. We propose one of these accretion events as the source of the observed warp in M33's disk.