1604.01400
A 17-billion-solar-mass black hole in a group galaxy with a diffuse core
Thomas, Ma, McConnell, Greene, Blakeslee, Janish
Detection of highly luminous quasars z>6 suggest that BHs up to ten billion Msun already existed 13 billion years ago. Two possible present-day dormant descendants of this population of active BHs have been found in the galaxies at the centers of the Leo and Coma galaxy clusters, which together form the central region of the Great Wall - the largest local structure of galaxies. The most luminous galaxy clusters, however, are not confined to such high-density regions of the early Universe; yet dormant BHs of this high mass have not yet been found outside of modern-day rich clusters. Report observations of the stellar velocity distribution in the galaxy NGC1600 - a relatively isolated elliptical galaxy near the center of a galaxy group at a distance of 64 Mpc from Earth. Use orbit superposition models to determine that the BH at the center has a mass of 17 billion Msun. The spatial distribution of stars near the centre is rather diffuse. Find that the region of depleted stellar density in the cores of massive elliptical galaxies extends over the same radius as the gravitational sphere of influence of the central BH, and interpret this as the dynamical imprint of the BHs.
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