Press Release

"Proto supermassive binary black hole detected in X-rays"

Astrophysicists at Bonn University's Argelander Institute für Astronomie, the U. S. Naval Research Lab, and the University of Virginia have detected two supermassive black holes using images obtained with NASA's Chandra X-ray Observatory. The black holes had been seen previously in radio images. The new X-ray data further strengthen the case that the black holes are physically close and form a bound system; i.e., they seem to form a real couple as opposed to being unrelated travellers on a road, caught by chance as they walk by each other.

Using the new Chandra data, the team have been able to spatially resolve the two supermassive black holes (separated by 0.004 degrees) at the centre of the merging galaxy cluster Abell 400. "The high resolution Chandra data allowed us to show that these two black holes are moving through the intracluster medium at the supersonic speed of about 1200 km/s," says Daniel Hudson, lead author of the submitted paper. The wind from such a motion would cause the radio plasma emitted from these two black holes to bend backwards. Although this bending had been observed previously, the cause of it was still being debated. Since the bending of the jets due to this motion is in the same direction, it suggests that the two black holes are travelling along the same path within the cluster and are therefore gravitationally bound.

The probable fate of these black holes is dim: several millions of years or more from now they will coalesce in a devilish dance while sending out cries of gravitational waves, as predicted by Einstein's theory of relativity. NASA's Laser Interferometer Space Antenna (LISA) will likely be able to measure such events directly.

Acknowledgements: This project was supported by the Deutsche Forschungsgemeinschaft through the Emmy Noether research programme and the National Aeronautics and Space Administration through a Chandra X-ray Observatory award. Basic Research in radio astronomy at NRL is supported by the Office of Naval Research. The National Radio Astronomy Observatory operates the VLA for the National Science Foundation under a cooperative agreement by Associated Universities, Inc.

Credits: D. Hudson, T. Reiprich (Bonn University); T. Clarke (Naval Research Lab & Interferometrics Inc.); C. Sarazin (University of Virginia).

X-ray detection of the proto supermassive binary black hole at the centre of Abell 400 by D.S Hudson, T.H. Reiprich, T.E. Clarke, and C.L. Sarazin.

To be published in Astronomy & Astrophysics (DOI number: 10.1051/0004-6361:20064955) Full article available in PDF format. Electronic edition of the press release available at http://www.edpsciences.org/aa. 		PR1.gif
This image shows the central region of the galaxy cluster Abell 400. The colour coding gives the temperature of the X-ray emitting gas trapped in the cluster: black-cold (18 million °C) to white-hot (38 million °C). The contours show the radio emission from the jets of plasma being expelled by the black holes. As the two black holes stream through the gas at supersonic velocities, the jets are bent toward the top of the image. The gas in front of the black holes is compressed and heated, as seen by the hotspot below them. The inset shows a blow up of the central regions. Each dot represents a position where an X-ray photon has struck Chandra's X-ray camera. The two black holes are seen as bright regions where as many as 250 X-ray photons struck the camera. The contours again show the radio emission from the black holes and the jets of plasma being ejected from them.
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This figure is a false colour image of Abell 400 on larger scales. The blue shows the Chandra image of the X-ray emitting gas (the lighter the blue, the brighter the emission) trapped in the gravitational field of Abell 400. This very diffuse gas (1 atom per litre) has more mass than the combined mass of the hundreds of galaxies in Abell 400. The elongation towards the bottom-right of the image is due to the fact that Abell 400 is merging with another cluster of galaxies. The radio emission (as described above) is shown in white. This image was created as part of a Chandra X-ray Center image release for Abell 400 and is available from their press office..