Enhancement of the tidal disruption event rate in galaxies with a nuclear star cluster: from dwarfs to ellipticals

Abstract

We compute the tidal disruption event (TDE) rate around local massive black holes (MBHs) with masses as low as 2.5×104M⊙⁠, thus probing the dwarf regime for the first time. We select a sample of 37 galaxies for which we have the surface stellar density profile, a dynamical estimate of the mass of the MBH, and 6 of which, including our Milky Way, have a resolved nuclear star cluster (NSC). For the Milky Way, we find a total TDE rate of ∼10−4yr−1 when taking the NSC in account, and ∼10−7yr−1 otherwise. TDEs are mainly sourced from the NSC for light (⁠<3×1010M⊙⁠) galaxies, with a rate of few 10−5yr−1⁠, and an enhancement of up to two orders of magnitude compared to non-nucleated galaxies. We create a mock population of galaxies using different sets of scaling relations to explore trends with galaxy mass, taking into account the nucleated fraction of galaxies. Overall, we find a rate of few 10−5yr−1 which drops when galaxies are more massive than 1011M⊙ and contain MBHs swallowing stars whole and resulting in no observable TDE.