The origin of the young stars in the nucleus of M31

The triple nucleus of M31 consists of a population of old red stars in an eccentric disk (P1 and P2) and another population of younger A stars in a circular disk (P3) around M31's central supermassive black hole (SMBH). We argue that P1 and P2 determine the maximal radial extent of the younger A star population and provide the gas that fueled the starburst that generated P3. The eccentric stellar disk creates an m = 1 nonaxisymmetric perturbation to the potential. This perturbed potential drives gas into the inner parsec around the SMBH, if the pattern speed of the eccentric stellar disk is Ω_p ≲ 3-10 km s^-1 pc^-1. We show that stellar mass loss from P1 and P2 is sufficient to create a gravitationally unstable gaseous disk of ∼10⁵ M_⊙ every 0.1-1 Gyr, consistent with the 200 Myr age of P3. Similar processes may act in other systems to produce very compact nuclear starbursts.