Could Segue 1 be a destroyed star cluster? - a dynamical perspective

Abstract

We attempt to find a progenitor for the ultrafaint object Segue 1 under the assumption that itformed as a dark matter free star cluster in the past. We look for orbits, using the elongationof Segue 1 on the sky as a tracer of its path. Those orbits are followed backwards in time tofind the starting points of our N-body simulations. The successful orbit, with which we canreproduce Segue 1 has a proper motion of μα = -0.19 mas yr-1 and μδ = -1.9 mas yr-1,placing Segue 1 near its apogalacticon today. Our best-fitting model has an initial mass of6224 M⊙ and an initial scalelength of 5.75 pc.