Evidence for a Long-Standing Top-Heavy IMF in the Central Parsec of the Galaxy

H. Maness(1), F. Martins(2), S. Trippe(2), R. Genzel(2, 3), J. R. Graham(1), C. Sheehy(4), M. Salaris(5), S. Gillessen(2), T. Alexander(6), T. Paumard(2), T. Ott(2), R. Abuter(2), F. Eisenhauer(2)

(1) Department of Astronomy, University of California at Berkeley, Berkeley, USA
(2) Max-Planck Institut f\ddotur extraterrestrische Physik (MPE), Garching, Germany
(3) Department of Physics, University of California at Berkeley, Berkeley, USA
(4) Department of Astronomy, University of Chicago, Chicago, USA
(5) Astrophysics Research Institute, Liverpool John Moores University, Liverpool, UK
(6) Faculty of Physics, Weizmann Institute of Science, Rehovot, Israel

Paper: ApJ, in press

EPrint Server: 0707.2382

Abstract:

We classify 329 late-type giants within 1 parsec of Sgr A^*, using the adaptive optics integral field spectrometer SINFONI on the VLT. These observations represent the deepest spectroscopic data set so far obtained for the Galactic Center, reaching a 50% completeness threshold at the approximate magnitude of the helium-burning red clump (K_S 15.5 mag.). Combining our spectroscopic results with NaCo H and K_S photometry, we construct an observed Hertzsprung-Russell diagram, which we quantitatively compare to theoretical distributions of various star formation histories of the inner Galaxy, using a \chi² analysis. Our best-fit model corresponds to continuous star formation over the last 12 Gyr with a top-heavy initial mass function (IMF). The similarity of this IMF to the IMF observed for the most recent epoch of star formation is intriguing and perhaps suggests a connection between recent star formation and the stars formed throughout the history of the Galactic Center.

Preprints available from the authors at hmaness@astro.berkeley.edu , or the raw TeX (no figures) if you click here.

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