Multifrequency Study of GHz-peaked Spectrum Sources

Gigahertz-Peaked spectrum (GPS) sources are compact active galactic nuclei, presumably young precursors of bright radio sources. The study of GPS radio properties provides information about the features of synchrotron radiation in extragalactic sources. Also in applied research, GPS sources are useful as compact stationary radio sources in the sky for astrometric purposes. This paper presents the results of a multifrequency GPS study based on quasi-simultaneous measurements with the RATAN-600 radio telescope during the 2006–2017 period. A catalog of GPS spectral flux densities at six frequencies—1.1, 2.3, 4.8, 7.7/8.2, 11.2, and 21.7 GHz—is obtained. In addition, for the analysis of radio spectra, data from low-frequency surveysGLEAM(GaLactic and Extragalactic AllskyMurchisonwidefield array survey) and TGSS (Tata institute for fundamental research GMRT Sky Survey) and high-frequency measurements from Planck survey are used. A total number of 164 GPS and candidates have been identified (17 of them are new discoveries), which makes up a small fraction of GPS in the initial sample of bright AGNs—about 2%. The physical properties and formation conditions of synchrotron radiation is found to be quite different in GPS of different AGNs types. The deficit of distant GPS (z > 2) with low maximum frequencies (less than 1 GHz) has been confirmed. The existing "size–peak frequency" anticorrelation is continuous. The continuum radio spectra are found to become statistically steeper with increasing redshift.