# # Program information file # PROGRAM_ID 2024B087 PROGRAM_TITLE Mid-infrared spectroscopy of rapidly growing active intermediate-mass black holes PROGRAM_INV1 Igor Chilingarian PROGRAM_INV2 Franz Bauer PROGRAM_INV3 Kirill Grishin PROGRAM_INV4 Evgenii Rubtsov PROGRAM_INV5 Victoria Toptun PROGRAM_SCICAT extra-galactic PROGRAM_ABSTRACT_BEG Confirmation of a population of intermediate black holes [IMBHs; MBH=1,000...100,000 MSun] will solve one of the long-standing problems in modern astrophysics, the origin of supermassive black holes [SMBHs]. IMBH host galaxies hold important clues to our understanding of galaxy formation and evolution processes: they might have evolved from ancient times in the early Universe without major merger events or intense gas accretion onto their nuclei and, therefore, represent the relics of primordial galaxy formation. Using publicly available X-ray data, we identify 7 unique IMBHs accreting close to the Eddington limit. Does intense BH growth in the IMBH regime affect their host galaxies? Does the growth rate stay persistent for extended periods of time? Is it the main IMBH growth channel? We propose mid-infrared spectroscopic observations of the 4 brightest active Eddington-limited IMBHs using SpeX in the 1.7-4.2um wavelength range to: [i] search for signatures of AGN-driven quenching by measuring the PAH 3.3um line; [ii] detect and measure broad Br-beta, Br-gamma, Pa-alpha hydrogen lines; [iii] search for coronal high-ionization Mg and Si lines predicted by IMBH accretion models. PROGRAM_ABSTRACT_END