Looking for Intermediate Mass Black Holes in GCs: The mass-segregation method

Intermediate Mass Black Holes (IMBHs; with mass in the 10² - 10⁴ M⊙ range) may be present in the cores of Globular Clusters (GCs). While the existence of IMBHs would have implications for galactic formation and evolution and GC dynamics, there has been no definitive detection of such an object to date. I present a new method for fingerprinting the presence of an IMBH which does not require information on the kinematics of GC stars and is applicable to collisionally relaxed GCs. Via two-body interactions, heavy stars sink to the center of a GC over several relaxation times, while lighter stars move to the periphery and preferentially evaporate from the system. N-body simulations show that the presence of an IMBH quenches such a mass segregation. The new method is based on comparing the observed GC mass segregation profile with predictions from N-body simulations with and without an IMBH. I compare a comprehensive set of such simulations to the mass segregation profile of NGC 2298 based on HST/ACS photometry and find that the presence of an IMBH greater than 300 solar masses can be rejected to the 3-σ level. Simulations without an IMBH also correctly predict the present day mass function of NGC 2298.