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arXiv · 0904.3326

Mass Segregation in NGC 2298: limits on the presence of an Intermediate Mass Black Hole

Mario Pasquato·Michele Trenti·Guido De Marchi·Michael Gill·Douglas P. Hamilton·M. Coleman Miller·Massimo Stiavelli·Roeland P. van der Marel
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Abstract

[abridged] Theoretical investigations have suggested the presence of Intermediate Mass Black Holes (IMBHs, with masses in the 100-10000 Msun range) in the cores of some Globular Clusters (GCs). In this paper we present the first application of a new technique to determine the presence or absence of a central IMBH in globular clusters that have reached energy equipartition via two-body relaxation. The method is based on the measurement of the radial profile for the average mass of stars in the system, using the fact that a quenching of mass segregation is expected when an IMBH is present. Here we measure the radial profile of mass segregation using main-sequence stars for the globular cluster NGC 2298 from resolved source photometry based on HST-ACS data. The observations are compared to expectations from direct N-body simulations of the dynamics of star clusters with and without an IMBH. The mass segregation profile for NGC 2298 is quantitatively matched to that inferred from simulations without a central massive object over all the radial range probed by the observations, that is from the center to about two half-mass radii. Profiles from simulations containing an IMBH more massive than ~ 300-500 Msun (depending on the assumed total mass of NGC 2298) are instead inconsistent with the data at about 3 sigma confidence, irrespective of the IMF and binary fraction chosen for these runs. While providing a null result in the quest of detecting a central black hole in globular clusters, the data-model comparison carried out here demonstrates the feasibility of the method which can also be applied to other globular clusters with resolved photometry in their cores.

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Mario Pasquato, Michele Trenti, Guido De Marchi, Michael Gill, Douglas P. Hamilton, M. Coleman Miller, Massimo Stiavelli, Roeland P. van der Marel. 2009-04-21. Mass Segregation in NGC 2298: limits on the presence of an Intermediate Mass Black Hole. https://doi.org/10.1088/0004-637x%2F699%2F2%2F1511

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