Research Byte

Published in the RSAA Lunations
Vol1 Issue6 1–31 July 2020

In a soon-to-be-submitted article we study the properties of the black hole at the centre of the quasar J2157. This quasar is the most luminous object in the Universe, and we found it nearly two years ago in the SkyMapper Southern Survey. The great luminosity of the quasar suggested that it harbours the fastest-growing black hole in the Universe and likely accretes the mass of our Sun every few days. We see the quasar (redshift 4.7) at a cosmic epoch of 1.25 billion years after the Big Bang.

For the new work, we used the X-Shooter spectrograph at the Very Large Telescope (VLT) of the European Southern Observatory (ESO). This is a powerful instrument, which we can access owing to Australia's strategic membership in ESO. From the emission lines in the spectra we were able to study the fast-moving gas orbiting the giant black hole at the centre of the quasar and to estimate the mass of its black hole. We find that this black hole already has a mass of 30 billion solar masses and is thus the most massive black hole known at this, or any earlier, epoch in the history of the Universe. That alone makes this object an attractive target for follow-up studies to learn what kind of galaxy it might live in.

https://arxiv.org/abs/2005.06868

Chris Onken, Fuyan Bian (now at ESO Chile) and Christian Wolf 

Image: A spectrum image from the X-Shooter spectrograph at the ESO Very Large Telescope (VLT).