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T.A. Rector, J.M. Wrobel, G.B. Taylor, S.T. Myers (NRAO), C.D. Fassnacht (STScI)
We are using the NRAO Very Long Baseline Array (VLBA) at 5 GHz to observe compact FIRST sources stronger than 10 mJy in the NOAO Deep Wide-Field Survey (NDWFS). Our study of 206 sources at milliarcsecond resolution overcomes two limitations of past VLBI surveys for active galactic nuclei (AGN), namely biases introduced by targeting flat-spectrum sources stronger than 200 mJy, plus the difficulty of obtaining deep optical identifications and redshifts. Half of the VLBA survey is complete, with almost one in three sources being detected above a typical threshold of 1.5~mJy~beam-1. Once complete, the VLBA detection rate will have enough statistical precision to constrain evolutionary models for radio source populations, such as a promising recent one based on a unification scheme for AGN (Jackson & Wall). Since the VLBA survey targets sources without spectral preselection, the detections will have implications for the interpretation of VLBA images of sources thought to be gravitationally lensed, and could potentially lead to the discovery of new types of AGN. All VLBA non-detections will still have astrophysical value, because of the visibility-function constraints from the VLBA and the identification information from the NOAO and Chandra surveys. This work made use of images provided by the NDWFS, which is supported by NOAO. NOAO is operated by AURA, Inc., under a cooperative agreement with the NSF. NRAO is a facility of the NSF operated under cooperative agreement by AUI.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.