AAS 205th Meeting, 9-13 January 2005
Session 155 X-ray Sources
Oral, Thursday, January 13, 2005, 10:00-11:30am, Golden Ballroom

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[155.08] VLA Observations of the CDFS and Hubble UDF

K.I. Kellermann, E.B. Fomalont (NRAO), J. Kelly (NRAO & UVa), P. Shaver, P. Rosati (ESO), P. Tozzi (INAF), V. Mainieri (MPE)

We have used the NRAO Very Large Array at 1.4 GHz to observe the Chandra Deep Field South, including the HST Ultra Deep Field, with an rms noise of 8 microJy and an angular resolution of 3.5 arcseconds. Additional observations were made at lower resolution of 11 arcseconds to detect low surface brightness features and at 5 GHz to obtain spectral information. Most of the observed radio emission is concentrated in small unresolved regions characteristic of an AGN, quasar, or small star forming region, but some sources contain extended features more typical of FRII radio galaxies. The radio data, combined with the X-ray data and the wealth of optical/IR material, help to distinguish between radio emission which is the result of star forming activity and that which is due to an AGN. Fifty-six or about thirty percent of the 185 radio sources above a limiting flux density of 40 microJy are catalogued X-ray sources, most, but not all, of which have optical counterparts brighter than mag 25. Of the remaining 129 radio sources, stacking of the X-ray data indicates a mean flux of 3.8 x 10-17 and 4.6 x 10-17 ergs sec-1cm-2 respectively in the soft and hard bands respectively. We also find that the stronger radio sources have smaller intrinsic X-ray absorbtion, while the large majority of sources less than 100 microJy have an HI density greater than 1022 cm-2. The NRAO is operated by AUI under cooperative agreement with the NSF.

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