Keck Spectroscopy of NGC 1052-DF9: Stellar populations in the context of the NGC 1052 Group

Abstract In this study, we use Keck/KCWI spectroscopy to measure the age, metallicity and recessional velocity of NGC 1052-DF9 (DF9), a dwarf galaxy in 1052 group. We compare these properties those two other galaxies group, 1052-DF2 1052-DF4, which have low dark matter content. The three are proposed constituents trail recently hypothesised formed as part ‘bullet dwarf’ collision. show that ages total metallicities within uncertainties one another may be expected if they share related formation pathway. However, recover for DF9 (1680 ± 10 km s−1) is higher than predicted linearly projected interpretation trail. then either not or correlation velocities along linear 2D projection due their 3D geometry. After examining pathways galaxies, none provide wholly satisfactory explanation all known properties. conclude further work required understand interesting group galaxies.