Oral Presentation

Cradle of seed black holes: ULXs and a possible IMBH in the blue compact dwarf galaxy NGC 4861

Author(s): Yi-Jung Yang (SHAO)

Presenter: Yi-Jung Yang (Shanghai Astronomical Observatory, Chinese Academy of Sciences)

There is growing evidence showing that, in addition to the stellar-mass and the central supermassive black holes, there is another class of black holes weighing in between the stellar-mass and supermassive, the so-called intermediate-mass black holes (IMBHs; 10^2-10^6 solar masses). In this talk, I will present our results on a possible IMBH in the center of Mrk 59 (also denoted as NGC 4861, which harbors two ULXs), which was not resolved in previous observations. Its location is coincident with a SDSS optical counterpart classified as galaxy. EVN observation also reveals a radio association within the region, indicating the presence of a jet. Using the fundamental plane relationship, we found the mass of the central black hole to be around 3x10^5 solar masses, that makes it fall in the range of IMBHs. If the low-mass nature is confirmed, this will be one of the very first active galactic nuclei in the intermediate mass range found in a blue compact dwarf galaxy (the local analogue of high-redshift galaxies) which will shed light on understanding the growth of black holes and the formation of galaxies in the early Universe.