The Quasar Sdss J105041.35+345631.3: Black Hole Recoil or Extreme Double-peaked Emitter?

The quasar SDSS J105041.35+345631.3 (z = 0.272) has broad emission lines blueshifted by 3500 km s relative to the narrow lines and the host galaxy. Such an object may be a candidate for a recoiling supermassive black hole, a binary black hole, a superposition of two objects, or an unusual geometry for the broad emission-line region (BLR). The absence of narrow lines at the broad line redshift argues against superposition. New Keck spectra of J1050+3456 place tight constraints on the binary model. The combination of large velocity shift and symmetrical Hβ profile, as well as aspects of the narrow line spectrum, make J1050+3456 an interesting candidate for black hole recoil. Other aspects of the spectrum suggest an extreme case of a double-peaked emitter. We discuss possible observational tests to determine the true nature of this exceptional object. Subject headings: galaxies: active — quasars: general — black hole physics