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In some galaxies, the stars orbiting the supermassive black hole take theform of an eccentric nuclear disk, in which every star is on a coherent,apsidally-aligned orbit. The most famous example of an eccentric nuclear diskis the double nucleus of Andromeda, and there is strong evidence for many morein the local universe. Despite their apparent ubiquity however, a dynamicalexplanation for their longevity has remained a mystery: differential precessionshould wipe out large-scale apsidal-alignment on a short timescale. Here weidentify a new dynamical mechanism which stabilizes eccentric nuclear disks,and explain for first time the negative eccentricity gradient seen in theAndromeda nucleus. The stabilizing mechanism drives oscillations of theeccentricity vectors of individual orbits, both in direction (about the meanbody of the disk) and in magnitude. Combined with the negative eccentricitygradient, the eccentricity oscillations push some stars near the inner edge ofthe disk extremely close to the black hole, potentially leading to tidaldisruption events. Order of magnitude calculations predict extremely high ratesin recently-formed eccentric nuclear disks ($\sim0.1 - 1$ ${\rm yr}^{-1} {\rmgal}^{-1}$). Unless the stellar disks are replenished, these rates shoulddecrease with time as the disk depletes in mass. If eccentric nuclear disksform during gas-rich major mergers, this may explain the preferentialoccurrence of tidal disruption events in recently-merged and post-merger(E+A/K+A) galaxies.

Dynamical Properties of Eccentric Nuclear Disks: Stability, Longevity, and Implications for Tidal Disruption Rates in Post-Merger Galaxies