Black hole feedback in the luminous quasar PDS 456

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Science  20 Feb 2015:
Vol. 347, Issue 6224, pp. 860-863
DOI: 10.1126/science.1259202

Finding the necessary negative feedback

The evolution of galaxies seems to be tied to the growth of the supermassive black holes at their centers, but it's not entirely clear why. Models have suggested a mechanism in which the growth of the black hole results in an outflow of gas that interrupts star formation. However, evidence for enough of this negative feedback has been lacking. Nardini et al. now see a signature in x-ray spectra of a strong persistent outflow in the quasar PDS 456. They estimate a broad solid angle spanned by the wind that enables a far greater impact on the host galaxy than narrower jet outflows.

Science, this issue p. 860


The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow’s kinetic power larger than 1046 ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution.

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