2018/06/12 by Ryan C. Hickox, David M. Alexander · 463 citations
Physics and Astronomy · #Accretion (finance) #Accretion disc #Active galactic nucleus #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #COSMIC cancer database #Galaxies: Formation, Evolution, Phenomena #Population #Radiative transfer #Supermassive black hole #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1146/annurev-astro-081817-051803
published in Annual Review of Astronomy and Astrophysics 56(1), 625-671 (Annual Reviews) · 50 pages, 16 figures. Invited review to appear in Annual Reviews of Astronomy and Astrophysics, Volume 56. An animated version of the schematic of AGN spectral energy distributions shown in Figure 4 is available at http://www.dartmouth.edu/~hickox/hickox_alexander_AGN.php
arxiv created 2018/06/12 · openalex created_date 2018/06/21 · openalex publication_date 2018/07/20 · arxiv updated 2018/10/17 · openalex updated_date 2026/08/06
Active galactic nuclei (AGN) are powered by the accretion of material onto a supermassive black hole (SMBH) and are among the most luminous objects in the Universe. However, the huge radiative power of most AGN cannot be seen directly, as the accretion is hidden behind gas and dust that absorb many of the characteristic observational signatures. This obscuration presents an important challenge for uncovering the complete AGN population and understanding the cosmic evolution of SMBHs. In this review, we describe a broad range of multiwavelength techniques that are currently being employed to identify obscured AGN, and we assess the reliability and completeness of each technique. We follow with a discussion of the demographics of obscured AGN activity, explore the nature and physical scales of the obscuring material, and assess the implications of obscured AGN for observational cosmology. We conclude with an outline of the prospects for future progress from both observations and theoretical models, and we highlight some of the key outstanding questions.