Double-Peaked Broad Emission Lines and the Geometry of Accretion in AGNs

Although accretion disks are a theoretically appealing model for the geometry and dynamics of the gas in the vicinity of black holes in Active Galactic Nuclei (AGN), there is little direct observational evidence for their existence. The telltale signature of disk emission in AGN -- double peaked emission lines -- have so far been found in only two dozen cases in the optical. We have selected about 100 double-peaked broad emission line AGN from the Sloan Digital Sky Survey (SDSS) from a large sample of over 4000 AGN with z<0.4. By comparing the properties of these AGN with those of the full sample, we hope to isolate the defining characteristics of disk-emitters and ultimately answer the question: "If all AGN have accretion disks, why don't they all show double-peaked disk emission lines?" Here we present Gaussian parameterized Halpha line-profile measurements for the sample of double-peaked AGN in comparison with circular and elliptical accretion disk models.