What is a cold quasar?

A cold quasar is a very active supermassive black hole whose host galaxy still has a lot of cold gas in it. The most massive of galaxies with the most massive of black holes become quasars. Quasars are the brightest objects in the universe due to how quickly they are accreting material. This material is superheated as it swirls around the black hole at nearly the speed of light. This turbulence can produce dramatic winds that sweep through the host galaxy, preventing new stars from being formed and essentially choking the host into becoming a passive, elliptical galaxy.

When we see luminous quasars without any dust in the very centre of the galaxy, the decline in star formation has already begun. Cold quasars were quite a surprise. This rare quasar has swept away dust from the galaxy centre, but the outskirts still have an abundance of cold gas and dust, producing thousands of new stars. Cold quasars are likely at the beginning of the end. The quasar influence is marching through the galaxy; soon the host will lose the ability to form new stars and enter the passive phase of its life.

Dr Allison Kirkpatrick, associate professor of physics and astronomy at the University of Kansas