The University of Southampton

Universe’s hidden supermassive black holes revealed

7 July 2015

An international team of scientists, including University of Southampton Astronomer Dr Poshak Gandhi, have found evidence for a large population of hidden supermassive black holes in the Universe.

Using NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) satellite observatory, the team detected the high-energy x-rays from five supermassive black holes previously clouded from direct view by dust and gas.

The research supports the theory that potentially millions more supermassive black holes exist in the Universe, but are hidden from view.

The findings were presented today at the Royal Astronomical Society’s National Astronomy Meeting, at Venue Cymru, in Llandudno, Wales (Monday 6 July).

NuSTAR satellite observatory

The scientists pointed NuSTAR at nine candidate hidden supermassive black holes, chosen by Dr Gandhi and the NuSTAR team, that were thought to be extremely active at the centre of galaxies, but where the full extent of this activity was potentially obscured from view.

High-energy x-rays found for five of the black holes confirmed that they had been hidden by dust and gas. The five were much brighter and more active than previously thought as they rapidly feasted on surrounding material and emitted large amounts of radiation.

Such observations were not possible before NuSTAR, which launched in 2012 and is able to detect much higher energy x-rays than previous satellite observatories. Dr Gandhi assisted the lead author George Lansbury, a postgraduate student at Durham University, with the data analysis.

A supermassive black hole

Dr Gandhi said: “These results are important for understanding how galaxies themselves grow and evolve, because we know that black holes feed on galaxies and can profoundly stunt the development of stars. The black holes that we looked at are cocooned within nests of interstellar gas and dust. The nests are their food, but also hide them from our sight. However, just like we can peer inside our chests with an X-ray machine, here we were able to look into the hearts of these supermassive black holes with the X-ray telescope NuSTAR, which is enabling us to peer deeper than ever before.”

The research was funded by the Science and Technology Facilities Council (STFC) and has been accepted for publication in the Astrophysical Journal.

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