Physics and Astrophysics colloquium is Dec. 4
A Physics and Astrophysics colloquium will begin at 4 p.m. Friday, Dec. 4, in 215 Witmer Hall. Wayne Barkhouse will present "SDSS J1254+0846: A Binary Quasar caught in the Act of Merging." Everyone is welcome to attend
Abstract: I will discuss the discovery of the first luminous spatially resolved binary quasar that clearly inhabits an ongoing galaxy merger. SDSS J125455.09+084653.9 and SDSS J125454.87+084652.1 (SDSS J1254+0846 A and B hereafter) are two luminous z=0.44 quasars, with a radial velocity difference of just 215 km/s, separated on the sky by 21 kpc in a disturbed host galaxy merger showing obvious tidal tails. The pair was targeted as part of a complete sample of binary quasars candidates with small transverse separations drawn from SDSS DR6 photometry. I will present follow-up optical imaging which shows broad, symmetrical tidal arm features spanning some 75 kpc at the quasar redshift. Semi-analytic modeling suggests that the system consists of two massive disk galaxies prograde to their mutual orbit, caught during the first passage of an ongoing merger. SDSS J1254+0846, as a pre-coalescence merger with two observed quasars, provides a unique opportunity to probe the early phases of the proposed merger/triggering mechanism, in this case with a nearly face-on system, showing rapid black hole growth during the early stages of a merger between galaxies with pre-existing bulges. Neither of the two luminous nuclei shows significant intrinsic absorption by gas or dust in our optical or X-ray observations, illustrating that not all merging AGN will be in an obscured, ultraluminous phase. We find that the Eddington ratio for the fainter component B is rather normal, while for A L/Ledd is quite (>3σ) high compared to quasars of similar luminosity and redshift, possibly evidence for strong merger-triggered accretion. More such mergers should be identifiable at higher redshifts using binary quasars as tracers.
-- Connie Cicha, secretary, Physics & Astrophysics, connie_cicha@und.nodak.edu, 777-2911 |