Numerical estimates of the accretion rate onto intermediate-mass black holes

TL;DR

This paper estimates the accretion rate onto intermediate-mass black holes in globular clusters, considering cluster-specific factors, and suggests that more massive clusters with high velocity dispersion are prime candidates for detecting such accretion.

Contribution

It introduces a new approach to estimate accretion rates that accounts for cluster properties, extending beyond traditional models.

Findings

Accretion rate depends on cluster characteristics, not just black hole mass.

More massive clusters with high velocity dispersion are better candidates for IMBH detection.

The estimated accretion rates differ from traditional Bondi-Hoyle predictions.

Abstract

The existence of intermediate-mass ($\sim 10^3 M_\odot$) black holes in the center of globular clusters has been suggested by different observations. The X-ray sources observed in NGC 6388 and in G1 in M31 could be interpreted as being powered by the accretion of matter onto such objects. In this work we explore a scenario in which the black hole accretes from the cluster interstellar medium, which is generated by the mass loss of the red giants in the cluster. We estimate the accretion rate onto the black hole and compare it to the values obtained via the traditional Bondi-Hoyle model. Our results show that the accretion rate is no longer solely defined by the black hole mass and the ambient parameters but also by the host cluster itself. Furthermore, we find that the more massive globular clusters with large stellar velocity dispersion are the best candidates in which accretion onto IMBHs could be detected.