https://phys.org/news/2018-11-galaxy-ngc-host-intermediate-mass-black.html

Although the list of known IMBH candidates contains hundreds of objects and is still expanding, none of them has been confirmed yet. Such black holes are generally difficult to find due to the fact that radii of their gravitational influence are too small to be resolved spatially, even in nearby galaxies. Therefore, one of the methods used by astronomers to identify IMBH candidates is to search for dwarf active galactic nuclei (AGNs).

A group of researchers led by Ning Jiang of the University of Science and Technology of China in Hefei, conducted such search for AGNs by analyzing data provided by space observatories like NASA's Chandra X-ray observatory, ESA's XMM-Newton spacecraft and the NASA/ESA Hubble Space Telescope (HST). The study led to the detection of a promising IMBH candidate in the nearby barred bulgeless galaxy designated NGC 3319, about 47 million light years away.