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Description
We present the first results from the deep and wide 5GHz radio observations of the Great Observatories Origins Deep Survey (GOODS)-North ({sigma}=3.5{mu}Jy/beam, synthesized beam size {theta}=1.47"x1.42", and 52 sources over 109arcmin^2^) and GOODS-South ({sigma}=3.0{mu}Jy/beam, {theta}=0.98"x0.45", and 88 sources over 190arcmin^2^) fields using the Karl G. Jansky Very Large Array. We derive radio spectral indices {alpha} between 1.4 and 5GHz using the beam-matched images and show that the overall spectral index distribution is broad even when the measured noise and flux bias are considered. We also find a clustering of faint radio sources around {alpha}=0.8, but only within S_5GHz_<150{mu}Jy. We demonstrate that the correct radio spectral index is important for deriving accurate rest-frame radio power and analyzing the radio-FIR correlation, and adopting a single value of {alpha}=0.8 leads to a significant scatter and a strong bias in the analysis of the radio-FIR correlation, resulting from the broad and asymmetric spectral index distribution. When characterized by specific star formation rates, the starburst population (58%) dominates the 5GHz radio source population, and the quiescent galaxy population (30%) follows a distinct trend in spectral index distribution and the radio-FIR correlation. Lastly, we offer suggestions on sensitivity and angular resolution for future ultra-deep surveys designed to trace the cosmic history of star formation and AGN activity using radio continuum as a probe.
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