Kavli Affiliate: Pau Amaro Seoane
| First 5 Authors: Sebastiano von Fellenberg, Stefan Gillessen, Julia Stadler, Michi Bauböck, Reinhard Genzel
| Summary:
We present a large ${sim 30" times 30"}$ spectroscopic survey of the
Galactic Center using the SINFONI IFU at the VLT. Combining observations of the
last two decades we compile spectra of over $2800$ stars. Using the
Bracket-$gamma$ absorption lines we identify $195$ young stars, extending the
list of known young stars by $79$. In order to explore the angular momentum
distribution of the young stars, we introduce an isotropic cluster prior. This
prior reproduces an isotropic cluster in a mathematically exact way, which we
test through numerical simulations. We calculate the posterior angular momentum
space as function of projected separation from Sgr~A*. We find that the
observed young star distribution is substantially different from an isotropic
cluster. We identify the previously reported feature of the clockwise disk and
find that its angular momentum changes as function of separation from the black
hole, and thus confirm a warp of the clockwise disk ($p sim 99.2%$). At large
separations, we discover three prominent overdensities of angular momentum. One
overdensity has been reported previously, the counter-clockwise disk. The other
two are new. Determining the likely members of these structures, we find that
as many as $75%$ of stars can be associated with one of these features. Stars
belonging to the warped clockwise-disk show a top heavy K-band luminosity
function, while stars belonging to the larger separation features do not. Our
observations are in good agreement with the predictions of simulations of
in-situ star formation, and argue for common formation of these structures.
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