Two Extreme Double-peaked Line Emitters in the Sloan Digital Sky Survey

Abstract

Double-peaked Balmer lines have been observed in about 150 AGNs and were interpreted preferably as emission from relativistic accretion disks. In this paper, we report the discovery of extreme double-peaked lines in SDSS J0942+0900 and SDSS J1417+6141. The FWHM of the Halpha line ~40,600 km/s in the first object is almost twice as large as the broadest one previously known. By comparing the line profile with accretion disk models, we find that most of the line flux is emitted from a narrow annulus around 100Rg in SDSS J0942+0900, and from a disk of radii between 100 and 400Rg in SDSS J1417+6141. This is the first time that an accretion disk at radii below 100Rg can be directly probed through optical emission lines. A certain asymmetry in the disk is required for both objects. Another much weaker broad Halpha component (EW~20A, and FWHM 4000km/s) is also detected in both objects. Both objects show weak radio emission and strong high-ionization narrow lines.