The response of relativistic outflowing gas to the inner accretion disk of a black hole

Michael L. Parker, Ciro Pinto, Andrew C. Fabian, Anne Lohfink, Douglas J. K. Buisson, William Alston, Erin Kara, Edward M. Cackett, Chia-Ying Chiang, Thomas Dauser, Barbara De Marco, Luigi C. Gallo, Javier Garcia, Fiona A. Harrison, Ashley L. King, Matthew J. Middleton, Jon M. Miller, Giovanni Miniutti, Christopher S. Reynolds, Phil Uttley, Ranjan Vasudevan, Dominic J. Walton, Daniel R. Wilkins and Abderahmen Zoghbi, 2017, Nature 543, 83–86

Active galactic nucleus (AGN) feedback is the process by which supermassive black holes in the centres of galaxies may moderate the growth of their hosts. Gas outflows from supermassive black holes release huge quantities of energy into the interstellar medium, clearing the surrounding gas. The most extreme of these, the ultra-fast outflows (UFOs), are the subset of X-ray detected outflows with velocities higher than 10,000 km/s, believed to originate in relativistic disc winds, a few hundred gravitational radii from the black hole. The absorption features produced by these outflows are variable, but no clear link has been found between the behaviour of the X-ray continuum and the energy or equivalent width of the outflow features due to the long time-scales of quasar variability. Here, we present the detection of multiple absorption lines from an extreme ultra-fast gas flow in the X-ray spectrum of the active galactic nucleus IRAS 13224-3809, at 0.236+/-0.006 times the speed of light (71,000 km/s), where the absorption is strongly anti-correlated with the emission from the inner regions of the accretion disk. If the gas flow is identified as a genuine outflow then it is in the fastest 5 per cent of such winds, and its variability is hundreds of times faster than in other variable winds, allowing us to observe in hours what would take months in a quasar. We find signatures of the wind simultaneously in both low and high energy detectors, which are consistent with a single ionized outflow, linking the two phenomena. The detection of the wind responding to the emission from the inner disk demonstrates a connection between accretion processes occurring on very different scales, with the X-rays from within a few gravitational radii of the black hole ionizing the relativistically outflowing gas as the flux rises.