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J.M. Wrobel, G. B. Taylor, S.T. Myers (NRAO), T.A. Rector (U of Alaska), C.D. Fassnacht (UC Davis)
To investigate the parsec-scale properties of faint extragalactic radio sources, we have used the NRAO VLBA at 5.0 GHz to image about 100 FIRST sources in the Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). Traditional VLBI surveys suffer from a paucity of redshifts and from biases introduced by targeting bright, flat-spectrum sources. Our VLBA survey uses phase referencing of FIRST sources to avoid these biases. Each FIRST source was selected at 1.4 GHz to be stronger than 10 mJy and to have a largest angular size less than 5 arcseconds. About one source in three was detected with the VLBA as stronger than 1.5-2.5 mJy (6-sigma) at 2-milliarcsecond resolution. Most VLBA detections were unresolved but four apparent doubles were discovered. These doubles could be Compact Symmetric Objects, young and rare systems offering insights into evolutionary models for radio galaxies and strong tests of unified schemes. Optical identifications to 26 magnitudes (5-sigma) at 2-arcsecond resolution are becoming available from the NDWFS. At these depths we expect that almost all FIRST sources will be identified, mostly with radio galaxies and quasars. Identifications are an essential prerequisite for redshifts and spectroscopic follow-up has already commenced. Our VLBA images either locate the active nuclei within the optical hosts, or impose upper limits on emission from the active nuclei. Chandra and SIRTF surveys, underway by others, will further constrain the spectral energy distributions of the active nuclei. The NDWFS and SIRTF data will also help assess the galaxy cluster environments of the active nuclei. 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.
The author(s) of this abstract have provided an email address for comments about the abstract: jwrobel@nrao.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.