HEAPOW: The Origin of UFOs? (2017 Apr 10)

bystander · Post by **bystander** » Mon Apr 10, 2017 2:44 pm

HEAPOW: The Origin of UFOs? (2017 Apr 10)

(Relatively) tiny supermassive black holes at the centers of galaxies can have an enormous effect on their entire host galaxy. That's because, as supermassive black holes swallow material near them, they can generate enormous amounts of radiation and powerful winds that sweep through the galaxy. Signatures of these strong winds have been detected in the X-ray emission from an assortment of galaxies with actively feeding black holes, and, because the speeds of these winds are a good fraction of the speed of light, astronomers call these winds ultra-fast outflows, or UFOs. The X-ray emission from an active galaxy is often variable, changing on a variety of unpredictable timescales, so it's been difficult to determine the relationship between the gas falling into the black hole and the ultra-fast outflow. But a new study with the XMM-Newton X-ray Observatory has shown, for the first time, a clear dependence of the strength of the outflow and the X-ray brightness of the material falling into the black hole. The image above shows the X-ray emission versus X-ray energy observed in a long (17 day!) observation of the active galaxy IRAS 13224-3809. The supermassive black hole at the center of IRAS 13224-3809 is extremely variable in X-rays, changing its brightness by factors of a hundred or more in only a few hours. The image above shows the distribution of X-rays from the supermassive black hole in three X-ray brightness states: high (blue), medium (green) and low (red). In the low brightness state, a strong dip is seen at energies between 8 and 9 kilo-electron volts (or keV). This dip is produced by absorption of X-rays from very near the supermassive black hole by the ultra-fast outflowing material far from the black hole. Detailed analysis of the XMM-Newton observation shows a clear correlation between the strength of this dip and the X-ray brightness of the supermassive black hole. This observation clearly shows that the UFO is responding to the amount of material being swallowed by the black hole.