The Stellar Cusp Around the Supermassive Black Hole in the Galactic Center

Abstract

We analyze deep near-IR adaptive optics imaging as well as new proper motion data of the nuclear star cluster of the Milky Way. The surface density distribution of faint stars peaks within 0.2&#34; of the black hole candidate SgrA*. The radial density distribution of this stellar &#39;cusp&#39; follows a power law of exponent 1.3-1.4. The K-band luminosity function of the overall nuclear stellar cluster (within 9&#34; of SgrA*) resembles that of the large scale, Galactic bulge, but shows an excess of stars at K<14. We find that most of the massive early type stars at distances 1-10&#34; from SgrA* are located in two rotating and geometrically thin disks. These disks are inclined at large angles and counter-rotate with respect to each other. Their stellar content is essentially the same, indicating that they formed at the same time. The star closest to SgrA* in 2002, S2, exhibits a 3.8 micron excess. We propose that the mid-IR emission either comes from the accretion flow around the black hole itself, or from dust in the accretion flow that is heated by the ultra-violet emission of S2.