The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation

T. Paumard(1), R. Genzel(1,2), F. Martins(1), S. Nayakshin(3,4), A. M. Beloborodov(5,6), Y. Levin(7,8), S. Trippe(1), F. Eisenhauer(1), T. Ott(1), S. Gillessen(1), R. Abuter(1), J. Cuadra(3), T. Alexander(9,10), A. Sternberg(11)

(1) Max-Planck Institut für extraterrestrische Physik (MPE), Giessenbachstrasse, 85748 Garching, Germany
(2) Department of Physics, University of California, 366 LeConte Hall, Berkeley, CA 94720, USA
(3) Max-Planck Institut für Astrophysik (MPA), Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
(4) Theoretical Astrophysics Group, Department of Physics & Astronomy, University of Leicester, Leicester, LE1 7RH, United Kingdom
(5) Physics Department and Columbia Astrophysics Laboratory, Columbia University, New York, USA
(6) Astro-Space Center of Lebedev Physical Institute, 84/32 Profsoyuznaya st., Moscow, 117997, Russia
(7) Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, Ontario, M5S 3H8, Canada
(8) Sterrewacht Leiden, Leiden University, P.O. Box 9513,NL-2300 RA Leiden, The Netherlands
(9) Faculty of Physics, Weizmann Institute of Science, Rehovot 76100, Israel, (10) William Z. and Eda Bess Novick career development chair, (11) School of Physics & Astronomy, Tel Aviv University, P.O. Box 39040, Tel Aviv 69978, Israel

Paper: ApJ, 2006, in press

EPrint Server: astro-ph/0601268

Abstract:

We report the definite spectroscopic identification of 40 OB supergiants, giants and main sequence stars in the central parsec of the Galaxy. Detection of their absorption lines have become possible with the high spatial and spectral resolution and sensitivity of the adaptive optics integral field spectrometer SPIFFI/SINFONI on the ESO VLT. Several of these OB stars appear to be helium and nitrogen rich. Almost all of the 80 massive stars now known in the central parsec (central arcsecond excluded) reside in one of two somewhat thick (<|h|/R> 0.14) rotating disks. These stellar disks have fairly sharp inner edges (R 1'') and surface density profiles that scale as R^-2. We do not detect any OB stars outside the central 0.5 pc. The majority of the stars in the clockwise system appear to be on almost circular orbits, whereas most of those in the `counter-clockwise' disk appear to be on eccentric orbits. Based on its stellar surface density distribution and dynamics we propose that IRS 13E is an extremely dense cluster (\rho_core >3*10⁸ M_sun pc^-3), which has formed in the counter-clockwise disk. The stellar contents of both systems are remarkably similar, indicating a common age of 6 +/-2 Myr. The K-band luminosity function of the massive stars suggests a top-heavy mass function and limits the total stellar mass contained in both disks to 1.5*10⁴ M_sun. Our data strongly favor in situ star formation from dense gas accretion disks for the two stellar disks. This conclusion is very clear for the clockwise disk and highly plausible for the counter-clockwise system.

Preprints available from the authors at paumard@iap.fr , or the raw TeX (no figures) if you click here.

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