Radio Properties of High-Redshift Galaxies at z≥ 1

Study of high-redshift radio galaxies (HzRGs) can shed light on the active galactic nuclei (AGNs) evolution in massive elliptical galaxies. The vast majority of observed high-redshift AGNs are quasars, and there are very few radio galaxies at redshifts z>3 . We present the radio properties of 173 sources optically identified with radio galaxies at z≥ 1 with flux densities S_1.4≥ 20 mJy. Literature data were collected for compilation of broadband radio spectra, estimation of radio variability, radio luminosity, and radio loudness. Almost 60 % of the galaxies have steep or ultra-steep radio spectra; 22 % have flat, inverted, upturn, and complex spectral shapes, and 18 % have peaked spectra (PS). The majority of the PS sources in the sample (20/31) are megahertz-peaked spectrum source candidates, i.e. possibly very young and compact radio galaxies. The median values of the variability indices at 11 and 5 GHz are V_S_11=0.14 and V_S_5=0.13 , which generally indicates a weak or moderate character of the long-term variability of the studied galaxies. The typical radio luminosity and radio loudness are L_5=10^43-10^44 erg s ^-1 and log R=3-4 respectively. We have found less prominent features of the bright compact radio cores in our sample compared to high-redshift quasars at z≥ 3 . The variety of the obtained radio properties shows the different conditions for the formation of radio emission sources in galaxies.