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Abstract: This paper introduces a new program to find high-redshift radio galaxies inthe southern hemisphere through ultra-steep spectrum USS selection. We definea sample of 234 USS radio sources with spectral indices alpha 408^843 < -1.0and flux densities S 408 > 200 mJy in a region of 0.35 sr, chosen bycross-correlating the revised 408 MHz Molonglo Reference Catalogue, the 843 MHzSydney University Molonglo Sky Survey and the 1400 MHz NRAO VLA Sky Survey inthe overlap region -40 deg < delta < -30 deg. We present Australia TelescopeCompact Array ATCA high-resolution 1384 and 2368 MHz radio data for eachsource, which we use to analyse the morphological, spectral index andpolarization properties of our sample. We find that 85 per cent of the sourceshave observed-frame spectral energy distributions that are straight over thefrequency range 408-2368 MHz, and that, on average, sources with smallerangular sizes have slightly steeper spectral indices and lower fractionallinear polarization. Fractional polarization is anti-correlated with fluxdensity at both 1400 and 2368 MHz. We also use the ATCA data to determineobserved-frame Faraday rotation measures for half of the sample.



Author: J. W. Broderick, J. J. Bryant, R. W. Hunstead, E. M. Sadler, T. Murphy University of Sydney

Source: https://arxiv.org/







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