# An intermediate-mass black hole in the centre of the globular cluster 47 Tucanae

## TL;DR

This paper presents evidence for a ~2300 solar mass intermediate-mass black hole at the center of globular cluster 47 Tucanae, inferred from pulsar dynamics, suggesting a non-accreting, gas-starved black hole that could be a seed for supermassive black holes.

## Contribution

It provides the first dynamical evidence for an intermediate-mass black hole in 47 Tucanae using pulsar data, challenging previous electromagnetic search results.

## Key findings

- Dynamical evidence for a ~2300 M_sun black hole in 47 Tucanae
- Black hole is likely not accreting, explaining lack of electromagnetic signals
- Supports the existence of a population of electromagnetically invisible black holes

## Abstract

Intermediate mass black holes play a critical role in understanding the evolutionary connection between stellar mass and super-massive black holes. However, to date the existence of these species of black holes remains ambiguous and their formation process is therefore unknown. It has been long suspected that black holes with masses $10^{2}-10^{4}M_{\odot}$ 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 objects. 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 black holes. Based on the lack of an electromagnetic counterpart upper limits of $2060 M_{\odot}$ and $470 M_{\odot}$ have been placed on the mass of a putative black hole in 47 Tucanae (NGC 104) from radio and X-ray observations respectively. Here we show there is evidence for a central black hole in 47 Tuc with a mass of M$_{\bullet}\sim2300 M_{\odot}$$_{-850}^{+1500}$ when the dynamical state of the globular cluster is probed with pulsars. The existence of an intermediate mass black hole in the centre of one of the densest clusters with no detectable electromagnetic counterpart suggests that the black hole is not accreting at a sufficient rate and therefore contrary to expectations is gas starved. This intermediate mass black hole might be a member of electromagnetically invisible population of black holes that are the elusive seeds leading to the formation of supermassive black holes in galaxies.