AGN unification: the hidden truth
Ed Moran (Wesleyan University)
Tuesday 30/07/2019 @ 14:00, Sala IV piano Battiferro
Seyfert galaxies have been traditionally classified into two groups based on the presence (type 1) or absence (type 2) of broad permitted emission lines in their optical spectra. The discovery of polarized broad lines in a number of narrow-line Seyferts has indicated that such objects are in fact normal Seyfert 1 nuclei whose innermost regions are obscured from our direct view by a dense, torus-like structure. By establishing a link between the two main classes of Seyfert galaxies, spectropolarimetry has led to significant progress in our understanding of the physics of active galactic nuclei (AGNs). But in some ways, spectropolarimetry has also been a hindrance to AGN unification. Polarized broad lines have been detected in fewer than half of Seyfert 2s observed in large surveys, and several studies have reported that physical differences exist between narrow-line AGNs that do and do not display evidence for a hidden broad-line region (HBLR). Modeling of the polarized broad H alpha profile in NGC 2110, combined with a new interpretation of HBLR non-detections, suggests instead a geometric solution to this aspect of the AGN unification puzzle.