Astron. Astrophys. 352, 406-414 (1999)

B 1933+503, a dusty radio quasar at z  2

Implications for blank field sub-mm surveys?

Scott C. Chapman ¹, Douglas Scott ¹, Geraint F. Lewisi ², Colin Borys ¹ and Gregory G. Fahlman <sup>1

1</sup> Department of Physics and Astronomy, University of British Columbia, Vancouver, B.C. V6T 1Z1, Canada
² Department of Physics and Astronomy, University of Victoria, Victoria B.C. V8W 3P6, Canada

Received 25 June 1999 / Accepted 1 October 1999

Abstract

We present a detailed mm-wave and optical study of the gravitational lens system B 1933+503, discovered by Sykes et al. (1998) in the radio. This object is probably the most complex lens system known, with 10 lensed components within a radius of one arcsecond. It is potentially important as a probe of the Hubble constant, although no optical counterpart has thus far been observed down to . We have obtained new sub-millimetre detections at 450 µm, 850 µm and 1350 µm. We have also constrained the possible dust emission from the proposed foreground lensing galaxy using a K-band adaptive optics image and CO(5-4) measurements. A lensing model is constructed, taking the foreground elliptical galaxy at as the lensing mass. From this we derive a scenario from which to model the sub-millimetre emission. Several arguments then point to the source in the B 1933+503 system lying above a redshift of 2. We speculate that unlensed relatives of this source may constitute a sizable fraction of the 850 µm source counts.

Key words: galaxies: active galaxies: quasars: individual: B 1933+503 galaxies: starburst cosmology: observations cosmology: gravitational lensing infrared: galaxies

Send offprint requests to: SChapman@ociw.edu

© European Southern Observatory (ESO) 1999

Online publication: December 2, 1999

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