BASS XXXVII: The role of radiative feedback in the growth and obscuration properties of nearby supermassive black holes

C. Ricci, T. T. Ananna, M. J. Temple, C. M. Urry, M. J. Koss, B. Trakhtenbrot, Y. Ueda, D. Stern, F. E. Bauer, E. Treister, G. C. Privon, K. Oh, S. Paltani, M. Stalevski, L. C. Ho, A. C. Fabian, R. Mushotzky, C. S. Chang, F. Ricci, D. Kakkad, L. Sartori, R. Baer, T. Caglar, M. Powell, F. Harrison

Submitted on 31 August 2022


We study the relation between obscuration and supermassive black hole (SMBH) growth using a large sample of hard X-ray selected Active Galactic Nuclei (AGN). We find a strong decrease in the fraction of obscured sources above the Eddington limit for dusty gas (logλEdd2) confirming earlier results, and consistent with the radiation-regulated unification model. This also explains the difference in the Eddington ratio distribution functions (ERDFs) of type 1 and type 2 AGN obtained by a recent study. The break in the ERDF of nearby AGN is at logλEdd=1.34±0.07. This corresponds to the λEdd where AGN transition from having most of their sky covered by obscuring material to being mostly devoid of absorbing material. A similar trend is observed for the luminosity function, which implies that most of the SMBH growth in the local Universe happens when the AGN is covered by a large reservoir of gas and dust. These results could be explained with a radiation-regulated growth model, in which AGN move in the NHλEdd plane during their life cycle. The growth episode starts with the AGN mostly unobscured and accreting at low λEdd. As the SMBH is further fueled, λEdd, NH and covering factor increase, leading AGN to be preferentially observed as obscured. Once λEdd reaches the Eddington limit for dusty gas, the covering factor and NH rapidly decrease, leading the AGN to be typically observed as unobscured. As the remaining fuel is depleted, the SMBH goes back into a quiescent phase.


Comment: Accepted for publication in ApJ

Subjects: Astrophysics - Astrophysics of Galaxies; Astrophysics - High Energy Astrophysical Phenomena