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Paper: Massive Young Stars in the Galactic Center
Volume: 439, The Galactic Center: a Window to the Nuclear Environment of Disk Galaxies
Page: 100
Authors: Bartko, H.; Martins, F.; Trippe, S.; Fritz, T. K.; Genzel, R.; Ott, T.; Eisenhauer, F.; Gillessen, S.; Paumard, T.; Alexander, T.; Dodds-Eden, K.; Gerhard, O.; Levin, Y.; Mascetti, L.; Nayakshin, S.; Perets, H. B.; Perrin, G.; Pfuhl, O.; Reid, M. J.; Rouan, D.; Zilka, M.; Sternberg, A.
Abstract: We summarize our latest observations of the nuclear star cluster in the central parsec of the Galaxy with the adaptive optics assisted, integral field spectrograph SINFONI on the ESO/VLT, which result in a total sample of 177 bona fide early-type stars. We find that most of these Wolf Rayet (WR), O- and B- stars reside in two strongly warped eccentric (<e> = 0.36±0.06) disks between 0.8'' and 12'' from SgrA*, as well as a central compact concentration (the S-star cluster) centered on SgrA*. The later type B stars (mK > 15) in the radial interval between 0.8'' and 12'' seem to be in a more isotropic distribution outside the disks. We observe a dearth of late-type stars in the central few arcseconds, which is puzzling. The stellar mass function of the disk stars is extremely top-heavy with a best fit power law of dN/dm α m–0.45±0.3. Since at least the WR/O-stars were formed in situ in a single star formation event ∼6 Myrs ago, this mass function probably reflects the initial mass function (IMF). The mass functions of the S-stars inside 0.8'' and of the early-type stars at distances beyond 12'' differ significantly from the disk IMF; they are compatible with a standard Salpeter/Kroupa IMF (best fit power law of dN/dm α m–2.15±0.3).
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