The close environments of accreting massive black holes are shaped by radiative feedback

• Published in: Nature (London) Vol. 549; no. 7673; pp. 488 - 491
• Main Authors: Ricci, Claudio, Trakhtenbrot, Benny, Koss, Michael J., Ueda, Yoshihiro, Schawinski, Kevin, Oh, Kyuseok, Lamperti, Isabella, Mushotzky, Richard, Treister, Ezequiel, Ho, Luis C., Weigel, Anna, Bauer, Franz E., Paltani, Stephane, Fabian, Andrew C., Xie, Yanxia, Gehrels, Neil
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 28.09.2017; Nature Publishing Group
• Subjects: 639/33/34/863; 639/33/34/864; Accretion disks; Black holes; Black holes (Astronomy); Deposition; Feedback; Gravitation; Gravity; Humanities and Social Sciences; letter; Luminosity; multidisciplinary; Natural history; Science; Stars & galaxies; Studies; Sublimation; Supermassive black holes; Universe
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/nature23906

Radiation pressure on dusty gas is the main physical mechanism that regulates the distribution of the circumnuclear material that obscures many supermassive black holes. Cleaning up the neighbourhood Most supermassive black holes that are accreting material, and are thereby 'active', are obscured by gas and dust. However, a decrease in obscuration with increasing accretion has been observed in several previous studies, but the origin of the relationship has been unclear. Claudio Ricci and colleagues have determined that radiation pressure on the dust and gas is the explanation. This means that most of the obscuring material is located within a few to a few tens of parsecs of the black hole. They conclude that the differences between obscured and unobscured black holes are driven by the mass-normalized accretion rate of the black hole. The majority of the accreting supermassive black holes in the Universe are obscured by large columns of gas and dust 1 , 2 , 3 . The location and evolution of this obscuring material have been the subject of intense research in the past decades 4 , 5 , and are still debated. A decrease in the covering factor of the circumnuclear material with increasing accretion rates has been found by studies across the electromagnetic spectrum 1 , 6 , 7 , 8 . The origin of this trend may be driven by the increase in the inner radius of the obscuring material with incident luminosity, which arises from the sublimation of dust 9 ; by the gravitational potential of the black hole 10 ; by radiative feedback 11 , 12 , 13 , 14 ; or by the interplay between outflows and inflows 15 . However, the lack of a large, unbiased and complete sample of accreting black holes, with reliable information on gas column density, luminosity and mass, has left the main physical mechanism that regulates obscuration unclear. Here we report a systematic multi-wavelength survey of hard-X-ray-selected black holes that reveals that radiative feedback on dusty gas is the main physical mechanism that regulates the distribution of the circumnuclear material. Our results imply that the bulk of the obscuring dust and gas is located within a few to tens of parsecs of the accreting supermassive black hole (within the sphere of influence of the black hole), and that it can be swept away even at low radiative output rates. The main physical driver of the differences between obscured and unobscured accreting black holes is therefore their mass-normalized accretion rate.