1702.02149
An intermediate-mass black hole in the centre of the globular cluster 47 Tucanae
Kiziltan, Baumgardt, Loeb
Intermediate mass BHs play a critical role in understanding the evolutionary connection between stellar mass and super-massive BHs. However, to date the existence of these species of BHs remains ambiguous and their formation process is therefore unknown. It has been long suspected that BHs with masses 1e2-4 Msun should form and reside in dense stellar systems. Therefore, dedicated observational campaigns have targeted globular cluster for many decades searching for signatures of these elusive objets. All candidates found in these targeted searches appear radio dim and do not have the X-ray to radio flux ratio predicted by the fundamental plane for accreting BHs. Based on the lack of EM counterpart upper limits of 2060 Msun and 470 Msn have been placed on the mass of a mutated BH in 47 Tuc from radio and X-ray observations, respectively. Here, show that there is evidence for a central BH in 47 Tuc wit ha mass of ~2200+1500-800 Msun when the dynamical state of the globular cluster is probed with pulsars. The existence of an intermediate mass BH in the centre of one of the densest clusters with no detectable EM counterpart suggests that the BH is not accreting at a sufficient rate and therefore contrary to expectations is gas starved. This intermediate mass BH might be a member of EM invisible population of BHs that are the elusive seeds leading to the formation of SMBHs in galaxies.
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