2007ApJ...666L..13B

Recent simulations of merging black holes with spin give recoil velocities from gravitational radiation up to several thousand kilometers per second. A recoiling supermassive black hole can retain the inner part of its accretion disk, providing fuel for a continuing QSO phase lasting millions of years as the hole moves away from the galactic nucleus. One possible observational manifestation of a recoiling accretion disk is in QSO emission lines shifted in velocity from the host galaxy. We have examined broad-line QSOs with measurable Hβ and [O III] from the Sloan Digital Sky Survey that have broad emission lines substantially shifted relative to the narrow lines. We find no convincing evidence for recoiling black holes carrying accretion disks. We place upper limits on the incidence of recoiling black holes in QSOs of 0.2% for kicks greater than 800 km/s, 0.08% for kicks greater than 2000 km/s, and 0.04% for kicks greater than 2500 km/s line-of-sight velocity.