• Yelda, S.
• Larkin, J.
• Do, Tuan
• Lu, Jessica
• Ghez, A.
• Morris, M. R.
• Matthews, K.

Abstract

We report on the structure of the nuclear star cluster in the innermost 0.16 pc of the Galaxy using the number density profile of dynamically relaxed stars. Using laser guide star adaptive optics in conjunction with the integral field spectrograph, OSIRIS, at the Keck 2 telescope, we are able to spectroscopically differentiate between the dynamically relaxed (〉 10 Gyr) population of stars and the unrelaxed young (6 Myr) population. This distinction is crucial for testing models of stellar cusp formation in the vicinity of a black hole, as only the old stars would have reached dynamical equilibrium in the potential of the black hole at this time. We find that contamination from young stars is significant, with more than twice as many young stars as old stars in our sensitivity range (K' 〈 15.5) at certain radii. Our preliminary analysis reveals a shallower power law slope for the surface density profile of old stars than predicted by theories of cusp formation and that was found by stellar counts without spectroscopic distinction. This shallow slope suggests that stellar collisions might be important for limiting red giant lifetimes, or that there is mass segregation resulting from interactions with a large population of unseen stellar remnants in this region.

Topics

• density
• impedance spectroscopy
• surface
• cluster