Bullying black holes prevent star formation in nearby elliptical galaxies
A new research has found that massive elliptical galaxies in the nearby Universe contain plenty of cold gas, but still they fail to produce new stars as jets from the central supermassive black hole heat or stir up the gas.
Norbert Werner from Stanford University in California, USA, who led the study, said that they looked at eight giant elliptical galaxies that nobody had looked at with Herschel before and they were delighted to find that, contrary to previous belief, six out of eight abound with cold gas.
The astronomers proceeded to investigate their sample of galaxies across the electromagnetic spectrum, since gas at different temperatures shines brightly at different wavelengths.
They used optical images to probe the warm gas - at slightly higher temperatures than the cold one detected with Herschel, and X-ray data from NASA's Chandra X-ray Observatory to trace the hot gas, up to tens of millions of K.
Werner said that in the six galaxies that are rich in cold gas, the X-ray data show tell-tale signs that the hot gas is cooling.
This is consistent with theoretical expectations: once cooled, the hot gas would become the warm and cold gas that is observed at longer wavelengths. However, in these galaxies the cooling process somehow stopped, and the cold gas failed to condense and form stars.
In the other two galaxies of the sample -- the ones without cold gas -- the hot gas does not appear to be cooling at all.
Raymond Oonk from ASTRON, the Netherlands Institute for Radio Astronomy, said that the contrasting behaviour of these galaxies may have a common explanation: the central supermassive black hole.
The results have been published in Monthly Notices of the Royal Astronomical Society.
(Posted on 26-02-2014)
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