A 17-billion-solar-mass black hole in a group galaxy with a diffuse core

• Published in: Nature (London) 2016-04, Vol.532 (7599), p.340-342
• Main Authors: Thomas, Jens, Ma, Chung-Pei, McConnell, Nicholas J., Greene, Jenny E., Blakeslee, John P., Janish, Ryan
• Format: Article
• Language: English
• Subjects: 639/33/34/124; 639/33/34/863; Accretion; Astronomical research; Astrophysics; Black holes; Black holes (Astronomy); Clusters; Elliptical galaxies; Galaxies; Gravitational waves; Humanities and Social Sciences; letter; Light; Masses; multidisciplinary; Observations; Quasars; Science; Spatial distribution; Star & galaxy formation; Stars; Stars & galaxies; Velocity; Velocity distribution
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature17197

The galaxy NGC 1600 is found to contain an enormous black hole of 17 billion solar masses—the first black hole of such a size to be found in an environment outside the richest clusters of galaxies. A supermassive black hole in an isolated galaxy The elliptical galaxy NGC 1600, although loosely associated with a group of fainter galaxies, is generally considered as an isolated galaxy. Jens Thomas et al . report the discovery of an enormous black hole of 17 billion solar masses at the centre of NGC 1600, the first black hole of such a size to be found in an environment outside the richest clusters of galaxies. The authors suggest this black hole as a candidate object for studies of general relativity with the Event Horizon Telescope, linking nine radio telescopes worldwide and due to begin operation in 2017. Quasars are associated with and powered by the accretion of material onto massive black holes; the detection of highly luminous quasars with redshifts greater than z  = 6 suggests that black holes of up to ten billion solar masses already existed 13 billion years ago 1 . Two possible present-day ‘dormant’ descendants of this population of ‘active’ black holes have been found 2 in the galaxies NGC 3842 and NGC 4889 at the centres of the Leo and Coma galaxy clusters, which together form the central region of the Great Wall 3 —the largest local structure of galaxies. The most luminous quasars, however, are not confined to such high-density regions of the early Universe 4 , 5 ; yet dormant black holes of this high mass have not yet been found outside of modern-day rich clusters. Here we report observations of the stellar velocity distribution in the galaxy NGC 1600—a relatively isolated elliptical galaxy near the centre of a galaxy group at a distance of 64 megaparsecs from Earth. We use orbit superposition models to determine that the black hole at the centre of NGC 1600 has a mass of 17 billion solar masses. The spatial distribution of stars near the centre of NGC 1600 is rather diffuse. We 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 black holes, and interpret this as the dynamical imprint of the black holes.