A View of AGN Accretion Flows by Means of Double-Peaked Emission Lines

Mike Eracleous (Pennsylvania State University)

Although broad optical double-peaked emission lines are relatively rare in the spectra of AGNs, they can serve as important diagnostic tools in the cases when they are observed. A good case can be made that these lines originate in the moderately relativistic portion of the accretion disk (between a few hundred and a few thousand gravitational radii). A comparison of the line profiles corresponding to different transitions (i.e., low- vs high-ionization lines) suggests that these objects host at least two broad-line emitting regions, which could be identified with the disk proper and an outflowing wind. Thus, the dynamics and ionization state of these gaseous structures can be studied separately. The profiles of double-peaked Balmer lines are observed to vary on time scales of years or longer (i.e., a few dynamical times or longer), which affords us a way of probing dynamical phenomena in the disks. Of particular interest is the prospect of testing scenarios that invoke waves, since these also offer a mechanism for angular momentum transport in the outer disk.

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