Research reveals the quasar H1821+643, despite its intense activity, has a minimal effect on its host galaxy, overturning expectations about the role of quasars.
- Astronomers have found a rapidly growing supermassive
The Impact of Quasars on Their Surroundings
Quasars are different than other supermassive black holes in the centers of galaxy clusters in that they pull in more material at a higher rate. Astronomers have found that non-quasar black holes growing at moderate rates influence their surroundings by preventing the intergalactic hot gas from cooling down too much. This regulates the growth of stars around the black hole.
The influence of quasars, however, is not as well known. This new study of H1821+643 that quasars — despite being so active — may be less important in driving the fate of their host galaxy and cluster than some scientists might expect.
Detailed Study Reveals Surprising Findings
To reach this conclusion the team used Chandra to study the hot gas that H1821+643 and its host galaxy are shrouded in. The bright X-rays from the quasar, however, made it difficult to study the weaker X-rays from the hot gas. The researchers carefully removed the X-ray glare to reveal what the black hole’s influence is, which is reflected in the new composite image showing X-rays from hot gas in the cluster surrounding the quasar. This allowed them to see that the quasar is actually having little effect on its surroundings.
Using Chandra, the team found that the density of gas near the black hole in the center of the galaxy is much higher, and the gas temperatures much lower, than in regions farther away. Scientists expect the hot gas to behave like this when there is little or no energy input (which would typically come from outbursts from a black hole) to prevent the hot gas from cooling down and flowing toward the center of the cluster.
A paper describing these results has been accepted into the Monthly Notices of the Royal Astronomical Society and is available online.
Reference: “A cooling flow around the low-redshift quasar H1821+643” by H R Russell, P E J Nulsen, A C Fabian, T E Braben, W N Brandt, L Clews, M McDonald, C S Reynolds, J S Sanders and S Veilleux, 27 January 2024, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stae026
The authors are Helen Russell (