AAS 201st Meeting, January, 2003
Session 58. Clusters of Galaxies at Many Wavelengths
Oral, Tuesday, January 7, 2003, 10:00-11:30am, 608-609

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[58.08] The Radio/Optical Morphology of Micro-Jansky Radio Sources

E. B. Fomalont, K. I. Kellermann (NRAO), L.L. Cowie (IfA), A.J. Barger (Univ of Wisconsin)

We have observed the SSA13 field (RA=13 23, DEC=42 38) using the VLA. At 1.4 GHz the rms noise is 5.0~\muJy with resolution 1.8'', at 8.4 GHz the rms noise is 1.5~\muJy with a resolution of 3.0''. Optical images at R-band and Z-band with 1.1'' seeing were obtained from the Subaru telescope. Over 900 radio sources were detected (528 in the complete sample) and the optical/radio registration <0.2'' permitted identification of >95% of the radio sources.

The radio/optical morphological properties of the sources are sorted into a small number of classifications and these properties are compared. Our main conclusions are: (1) About half of the radio sources are associated with a relatively isolated galaxy; most other identifications are with binary systems. (2) Only 7 extended AGN (>5'') are found. (3) At Z-band, 8% of the sources are fainter than 26 mag. (4) The slope of the differential radio count is -2.3 with a density of 2.0 sources (amin)-2 with a flux density >27.5~\muJy. (5) The average radio angular size is 1.35'', but very few sources are larger than 5''. (6) The radio orientation is often correlated with the galaxy identification or binary system orientation.

Two correlations in these data suggest that most sources are associated with distant galaxies dominated by starburst activity. (1) The radio sources with angular size >1'' show an Infrared/radio correlation, whereas smaller-diameter sources do not; and (2) The radio spectral index steepens for sources weak then 100~\muJy, suggesting an even lower proportion of AGN at the fainter observed levels.

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Bulletin of the American Astronomical Society, 34, #4
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