Extending a bona fide IMBH sample\: X-ray confirmation of optical AGN candidates

A population of intermediate black holes (IMBH) will allow us to solve one ofthe longstanding problems in modern astrophysics, the origin of supermassiveblack holes. Using dedicated analysis of 1 million optical spectra, weidentified a sample of 305 IMBH candidates (3e4<M<2e5 M_Sun), which reside ingalaxy centers and pose as AGN. With XMMNewton and Chandra DDT observations in2017 and mining Xray data archives, we confirmed the AGN nature of 10candidates, thus validating our IMBH search approach. Here we propose to observe13 additional optically selected IMBH candidates in order to double the numberof Xray confirmed accreting IMBHs. This will enable detailed studies of theIMBH population and help to constrain the masses of seed black holes in the early Universe. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]