Optical spectroscopic observations of intermediate-mass black holes and their host galaxies: the $M_{BH}-{\sigma }_{\ast }$ relation

Abstract

Intermediate-mass black holes (IMBHs; $M_{BH}<2\ast 10^5{M}_{\odot }$) in galaxy centers are cruciel for painting a coherent picture of the formation and growth of supermassive black holes (SMBHs). Using Big Data analysis, we identified 305 IMBH candidates for IMBH and 1623 candidates of `light-weight' SMBHs ($2\ast 10^5{M}_{odot}<M_{BH}<10^6{M}_{\odot }$). For 35 host galaxies from this combined sample with the X-ray-confirmed active galactic nuclei (AGN) we collected and analyzed optical spectroscopic observations. These data show that bulge stellar velocity dispersions (${\sigma }_{\ast }$) lie in the range of 24$\dots$118~km/s and do not follow the correlation with $M_{BH}$ established by larger SMBHs indicating that in the $10^5-10^6{M}_{\odot }$ range the accretion is the prevailing BH growth channel.

5 pages, 7 figures. Astronomy at the epoch of multimessenger studies. Proceedings of the VAK-2021 conference, Aug 23-28, 2021 - Moscow, 2021