Radio-Optical Analysis of Extended Radio Sources in the First Look Survey Field

摘要

We combine 610 MHz GMRT data, 1.4 GHz VLA data, and 1.4 GHz WSRT obser-vations, encompassing a ti 4 square degree field centered on the verification strip of the Spitzer First Look Survey field, to study radio sources down to fluxes of about 0.1 mJy. The spectral index (Figure 1) analysis shows that the majority of multi-component sources are steep-spectrum sources. Nevertheless the spread in the spectral distribution is wide, with a significant number of ultra-steep, flat or inverted sources, possibly indicating a wider range of accretion modes in fainter samples. By cross-correlating 107 multi-component radio sources with the optical catalogues of Marleau et al. (2007) and Pa-povich et al. (2006), 23 objects were identified. The measured redshifts span the range 0 < z < 1.8 and peak at z — 0.2. According to their radio power, six of the identified objects are in the range of FR II sources while 17 are in the range of FR I sources. Further optical follow-up will allow a more complete census of the sub-mJy population and more information on AGN feedback from such sources.