Growth of supermassive black holes in the "light-weight" regime: the insights from the local Universe

Monday, 28 November 2022 7 a.m. — 8 a.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
Igor Chilingarian (CfA/SAO)

A central supermassive black hole (SMBH) can be found in almost every massive galaxy in the local Universe, however there is no understanding on how the growth of SMBH occurred in the early stages of galaxy formation. It is still debated whether SMBHs originated from "light" (i.e. stellar mass BHs, 1e2 MSun) or "heavy" (i.e. direct collapse BHs 1e5 MSun) seeds. I will present our multi-wavelength observational campaign and discuss how the recent advances in the search of intermediate-mass black holes (IMBHs, 1e2 to 1e5 MSun) in the local Universe can help us to clarify the question of the SMBH formation. I will provide direct evidences of the IMBH growth by both intense accretion and via BH coalescence by: (1) presenting a sample of Eddington-limited and mildly super-Eddington IMBHs; (2) demonstrating the first example of an active 10:1 mass ratio IMBH binary hosted by a morphologically disturbed dwarf galaxy which perhaps experienced a recent minor merger. Understanding which of the two growth channels prevailed in the early Universe has a huge impact on our ability to detect black holes at high redshifts with next-generation facilities: if (super-)Eddington growth dominates then a EUV/X-ray mission (e.g. Athena) will become indispensable; if the growth happens mainly via mergers then LISA will become the key player.