Fast-flowing gas curtails galaxy’s glow
The bright core of a spiral galaxy has unexpectedly dimmed, according to a new study by an international team of astronomers. The nucleus of galaxy NGC 5548, which contains a region of powerful X-ray light surrounding the galaxy's central black hole, has been obscured by a fast-flowing stream of gas. Such behaviour, which is rarely seen in the heart of this type of galaxy, casts new light on the poorly-understood processes governing the interaction between galaxies and their central black holes. Published in Science today, the study provides the first direct evidence for the long-predicted shielding process that is needed to accelerate powerful gas streams, or "winds," to high speeds. "This is a milestone in understanding the interaction of supermassive black holes and their host galaxies." says Professor Graziella Branduardi-Raymont, one of the researchers from UCL Mullard Space Science Laboratory (MSSL). She added, "I was delighted when our consortium agreed to focus the campaign on NGC 5548, as I first became interested in this active galaxy almost three decades ago, observing it with the X-ray instruments operating in space at the time." In 2013 and 2014 the team including researchers from UCL, University of Cambridge and University of Oxford, led by Dr Jelle Kaastra, SRON Netherlands Institute for Space Research, conducted the most extensive monitoring campaign of an active galaxy ever with major ESA and NASA space observatories: XMM-Newton, the Hubble Space Telescope, Swift, NuSTAR, Chandra, and INTEGRAL.
