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K. M. Chynoweth (NRAO/Colorado College), T. A. Rector, J. M. Wrobel, G. B. Taylor (NRAO), C. D. Fassnacht (UC-Davis), S. T. Myers (NRAO)
The NRAO VLBA was used at 5.0 GHz to image 53 FIRST sources in the Cetus field of the NOAO Deep Wide-Field Survey (NDWFS). The FIRST sources were chosen to have compact angular sizes and peak flux densities > 10 mJy/beam, and are therefore expected to be active galaxies. Active nuclei were detected in nine of these FIRST sources with the VLBA at 4-milliarcsecond resolution, above an average 6\sigma threshold of about 1.9 mJy/beam. The peak values of the detections ranged from 2.5 mJy/beam to 143 mJy/beam, with an average peak value of 28.9 mJy/beam. Eight of the detections were point sources, while the ninth has complex extended structure. The 44 sources not detected could still contain active nuclei weaker than 1.9 mJy/beam at 5.0 GHz. Therefore, at least 17±8% of compact FIRST sources contain active nuclei. This is lower than the corresponding value for the Boötes field of 32±6%, but not by a statistically significant amount. Percentage recovered flux density and spectral index were calculated and compared for all sources. It was expected that for the VLBA detections, the spectral index would steepen as the percentage recovered flux decreased. The expected relationship was confirmed.
This work was conducted as a part of the NRAO Summer Student Program. Funding was provided by the NSF REU program.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.