Space Telescope Science Institute

The Star Formation History and Evolution of the Ultra-Diffuse M81 Satellite F8D1

Abstract We present deep Hubble Space Telescope (HST) imaging of one of the nearest ultra-diffuse galaxies (UDGs) outside of the Local Group: F8D1, a satellite of M81 known to be tidally disrupting. UDGs are an enigmatic and diverse population, with evolutionary pathways ranging...

Evidence of a massive accretion event 1.8 billion years before the Gaia-Sausage-Enceladus merger

Abstract The merger history of the Galaxy has been traced back firmly to a redshift of 2 (10 billion years ago). While evidence for the existence of at least one more substantial merger before this time has been presented, its interpretation is yet to be fully established. Here w...