This project is linked to the research of Prof. Ian McHardy in the astronomy group at the University of Southampton (UoS). Ian’s research area focuses on Active Galactic Nuclei (AGN), these are supermassive black holes that exist at the centres of galaxies and are very active. When we say ‘very active’ we mean they have features like an accretion disc and/or jet and these extreme environments give off radiation with wavelengths spanning the whole electromagnetic spectrum. Dr Sadie Jones’ PhD research at UoS was also on AGN, specifically in understanding these mysterious objects by using a combination of radio, X-ray and optical telescopes.
The most massive of black holes are the masses of over a million Suns and live at the centre of galaxies. Our Milky way galaxy has a black hole the size of 4 million Suns. And some galaxies have very bright centres and this is because they have very ‘active’ supermassive blackholes, we call these Active Galactic Nuclei or AGN. For these blackholes astronomers have worked out that there is a disc of material that swirls around the black hole which is called an accretion disc and there is a corona, that scientists still don’t know the exact shape of.
Even massive telescopes like Hubble are not powerful enough to see the visible light from these discs. However, we can see the X-ray light from the accretion disc and the corona using our X-ray Telescopes, which are up above the Earth, in space.
Some active galaxies also have jets which we are think are launched near the event horizon of the black hole. We see these jets because they give of radio waves that we detect using large radio dishes that are all connected via the internet. It’s possible that the disc /corona and jet regions are linked by the same energy reservoir. In other words, if energy goes into the X-rays, it must be taken away from the radio.
The way to understand where the light is coming from is to study radio and X- ray light curve graphsfrom these active supermassive blackholes and look for a relationship between them.
If X-rays are emitted from the corona around the black hole, they will travel outwards and hit the surrounding material, where they will be re-emitted as lower energy radiation and reverberate. By measuring the time delay between the X-rays and the lower energy emission we can measure how far apart the corona and jets are and learn about the dimensions of the supermassive black hole system.
Astronomers use X-ray telescopes in space and radio telescopes on the Earth to look at lots of different AGNs. Then they collect all this data on lots of different black holes with many different masses and see if they can see any patterns in the X-ray/ radio relationship.
Dr Sadie Jones & Prof Ian McHardy