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Astrophysics, Galaxy Astrophysics, astro-ph.GA
Abstract:
The existence of "S-stars" within a distance of 1" from SgrA$^*$ contradicts
our understanding of star formation, due to the forbiddingly violent
environment. A suggested possibility is that they form far and have been
brought in by some fast dynamical process, since they are young. Nonetheless,
all conjectured mechanisms either fail to reproduce their eccentricities
--without violating their young age-- or cannot explain the problem of "inverse
mass segregation": The fact that lighter stars (the S-stars) are closer to
SgrA$^*$ and more massive ones, Wolf-Rayet (WR) and O-stars, are farther out.
In this Letter we propose that the responsible for both, the distribution of
the eccentricities and the paucity of massive stars, is the Kozai-Lidov-{\em
like} resonance induced by a sub-parsec disk recently discovered in the
Galactic center. Considering that the disk probably extended to smaller radius
in the past, we show that in as short as (a few) $10^6$ years, the stars
populating the innermost 1" region would redistribute in angular-momentum space
and recover the observed "super-thermal" distribution. Meanwhile, WR and
O-stars in the same region intermittently attain ample eccentricities that will
lead to their tidal disruptions by the central massive black hole. Our results
provide new evidences that SgrA$^*$ was powered several millions years ago by
an accretion disk as well as by tidal stellar disruptions.
