The surface density profile of NGC 6388: a good candidate for harboring an intermediate-mass black hole

TL;DR

This study combines high-resolution and wide-field observations to analyze NGC 6388's density profile, suggesting it likely hosts an intermediate-mass black hole based on observed deviations from standard models.

Contribution

The paper provides detailed observational analysis and modeling indicating the presence of an intermediate-mass black hole in NGC 6388, a novel finding for this cluster.

Findings

Detection of a power-law deviation in the core profile

Modeling supports a black hole of ~5.7x10^3 solar masses

Profiles fit well with a multi-mass isotropic model

Abstract

We have used a combination of high resolution (HST ACS-HRC, ACS-WFC, and WFPC2) and wide-field (ESO-WFI) observations of the galactic globular cluster NGC 6388 to derive its center of gravity, projected density profile, and central surface brightness profile. While the overall projected profiles are well fit by a King model with intermediate concentration (c=1.8) and sizable core radius (rc=7"), a significant power law (with slope \alpha=-0.2) deviation from a flat core behavior has been detected within the inner 1 arcsecond. These properties suggest the presence of a central intermediate mass black hole. The observed profiles are well reproduced by a multi-mass isotropic, spherical model including a black hole with a mass of ~5.7x10^3 Msol.