Dynamical Friciton near the Galactic Center

Numerical simulations of the dynamical friction suffered by a star cluster near the Galactic center have been performed with a parallelized tree code. Gerhard (2001) has suggested that dynamical friction, which causes a cluster to lose orbital energy and spiral in towards the galactic center, may explain the presence of a cluster of very young stars in the central parsec, where star formation might be prohibitively difficult owing to strong tidal forces. The clusters modeled in our simulations have an initial total mass of 105–106 M⊙ and initial galactocentric radii of 2.5–30 pc. We have identified a few simulations in which dynamical friction indeed brings a cluster to the central parsec, although this is only possible if the cluster is either very massive (∼ 106M⊙), or is formed near the central parsec (≲5 pc). In both cases, the cluster should have an initially very dense core (>106M⊙pc−3). The initial segregation of massive stars into the cluster core can help achieve the requisite density, and can help account for the observed distribution of He I stars in the central parsec.