* Astronomy

Title: SDSS 0956+5128: A Broad-line Quasar with Extreme Velocity Offsets
Authors: Charles L. Steinhardt (1), Malte Schramm (1), John D. Silverman (1), Rachael Alexandroff (2), Peter Capak (3), Francesca Civano (4), Martin Elvis (4), Dan Masters (5,6), Bahram Mobasher (5), Petchara Pattarakijwanich (2), Michael A. Strauss (2) ((1) Kavli IPMU, (2) Princeton, (3) Caltech, (4) Harvard-Smithsonian CfA, (5) UC Riverside, (6) Carnegie)

We report on the discovery of a Type 1 quasar, SDSS 0956+5128, with a surprising combination of extreme velocity offsets. SDSS 0956+5128 is a broad-lined quasar exhibiting emission lines at three substantially different redshifts: a systemic redshift of z ~ 0.714 based on narrow emission lines, a broad MgII emission line centred 1200 km/s bluer than the systemic velocity, at z ~ 0.707, and broad H\alpha and H\beta emission lines centred at z ~ 0.690. The Balmer line peaks are 4100 km/s bluer than the systemic redshift. There are no previously known objects with such an extreme difference between broad MgII and broad Balmer emission. The two most promising explanations are either an extreme disk emitter or a high-velocity black hole recoil. However, neither explanation appears able to explain all of the observed features of SDSS 0956+5128, so the object may provide a challenge to our general understanding of quasar physics.

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Ed ~ Type 1 quasars are seen 'face-on', in Type 2 quasars the BH torus is seen 'edge-on'