Obscured Binary Quasar Cores in SDSS J104807.74+005543.5?

Abstract

We report the discovery of a possible close binary system of quasars in SDSS\nJ1048+0055. The [OIII]4959,5007 emission lines are clearly double-peaked, and\ntwo discrete radio sources with a projected physical separation of ~20 pc are\nfound in the VLBA milliarcsec resolution image at 8.4 GHz. Each of the [O\nIII]4959,5007 doublets and Hbeta can be well modelled by two Gaussians and the\nline ratio, [O III]5007/Hbeta ~7, is typical of Seyfert 2 galaxies. No broad\ncomponent of Hbeta was detected and its [O III]5007 luminosity, L_[OIII] ~ 9.2\ntimes 10^42 erg s^-1, is comparable to luminous quasars and is a few ten times\nmore luminous than typical Seyfert galaxies. One natural interpretation is that\nSDSS J1048+0055 contains two close quasar-like nuclei and the BLR around them\nare obscured. Other possible models are also discussed. We suggest that\ndouble-peaked narrow emission line profile may be an effective way of selecting\ncandidates of binary black holes with intermediate separation.\n