High-speed outflow keeps black holes in check

Daily Mail : The puzzling correlation between the mass of a galaxy’s central black hole and the number of stars in the galaxy may be explained by streams of fast-moving, highly ionized gas emitted from the black hole’s accretion disk. Francesco Tombesi of NASA’s Goddard Space Flight Center examined data gathered from the European Space Agency’s XMM-Newton x-ray observatory and discovered that these streams, called ultrafast outflows, exert a powerful influence on the number of stars in galaxies and the size of black holes at their center. The outflows establish a feedback mechanism in the host galaxy by taking material from around the black hole and ejecting it at speeds of up to 100 000 km/s. The ejected material would otherwise have been used in star formation or fallen into the black hole. Removing it limits both the size of the black hole and the number of stars in the galactic center.