Optical spectroscopy of host-galaxies of intermediate mass black holes: evolution of central black holes

TL;DR

This study investigates intermediate-mass black holes in galaxy centers through optical spectroscopy, revealing their properties, growth mechanisms, and challenging the co-evolution paradigm with host galaxies.

Contribution

It provides a detailed analysis of IMBH candidates, including the first detection of a binary IMBH system, and refines methods for estimating black hole masses.

Findings

Detection of a binary black hole system with masses 1.7e5 and 1.4e6 solar masses

IMBHs may grow via super-Eddington accretion, not necessarily co-evolving with host galaxies

Enhanced accuracy in virial mass estimates and insights into the M_BH - sigma_bulge relation

Abstract

Intermediate-mass black holes (IMBHs) with masses below ($2 \times 10^5 M_{\odot}$) are pivotal in understanding the origin and growth mechanisms of supermassive black holes (SMBHs) in galactic nuclei. This study focuses on the search and detailed analysis of central lightweight black holes in various galaxies. An expanded sample of IMBH candidates was selected from the RCSED optical spectral catalog, followed by refined spectral observations using large telescopes, including the Magellan, SALT, Keck and CMO telescopes. Analyzing over 70 spectra, we obtained accurate virial masses, stellar population parameters, and kinematics. One significant finding includes the detection of a binary black hole system with masses ($1.7 \times 10^5 M_{\odot})$ and $(1.4 \times 10^6 M_{\odot}$). Our results indicate that IMBHs and their low-mass SMBH counterparts do not necessarily co-evolve with their host galaxies, suggesting super-Eddington accretion as a dominant growth mechanism. This research enhances the precision of virial mass estimates and offers new insights into the $M_{BH} - \sigma_{bulge}$ relation, potentially impacting future high-redshift SMBH observations using next-generation facilities.