Discovery of a Radio-loud/radio-quiet Binary Quasar

Abstract

We report the discovery of a small separation quasar pair (z = 0.586, O = 18.4, 19.2, sep. = 2. 3) associated with the radio source FIRST J164311.3+315618 (S1400 = 120 mJy). The spectrum of the brighter quasar (A) has a much stronger narrow emission-line spectrum than the other (B), and also stronger Balmer lines relative to the continuum. The continuum ratio of the spectra is flat in the blue (λobs < 6000 Å) at about 2.1, but falls to 1.5 at longer wavelengths. A K ′ image shows two unresolved sources with a flux ratio of 1.3. The different colors appear to result from the contribution of the host galaxy of B, which is evident from Ca II and high-order Balmer absorption lines indicative of a substantial young stellar population. New 3.6 cm VLA observations show that the compact radio source is coincident with quasar A (B is only marginally detected). We rule out the lensing hypothesis because the optical flux ratio is A/B ≈ 1.5–2 while the radio flux ratio is A/B ∼ > 40, and conclude that this system is a binary. Moreover, the radio-loud quasar is a compact steep spectrum source. FIRST J164311.3+315618A, B is the lowest redshift and smallest separation binary quasar yet identified. Subject headings: galaxies: evolution, galaxies: interactions, quasars: emission lines, quasars: general

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@inproceedings{Brotherton2008DiscoveryOA, title={Discovery of a Radio-loud/radio-quiet Binary Quasar}, author={Michael S. Brotherton and Michael Gregg and Robert Becker and S. A. Laurent-Muehleisen}, year={2008} }