Multifrequency study of GHz-peaked spectrum sources and candidates with the RATAN-600 radio telescope

Abstract

Context. Gigahertz peaked spectrum (GPS) radio sources are a class of extragalactic radio sources characterized by a spectral peak in the gigahertz domain. They are a mixed class of quasars and galaxies. A large proportion of the sources studied in the literature have only few data points in the radio domain, and the determination of variability and shape of the simultaneous spectra is inadequate. Sources currently included in the GPS source lists are very heterogeneous. Aims. We present the observational results from 12 observing campaigns (carried out between 2006 and 2010) at the RATAN-600 radio telescope to obtain the simultaneous radio spectra, which is valuable and necessary to derive genuine GPS sources from flatspectrum radio sources caught in a flaring state when their spectra are temporarily inverted. The sample contains both quasar-and galaxy-type GPS (122 sources) identified in the literature. Methods. The observations were carried out at six frequencies (1.1, 2.3, 4.8, 7.7, 11.2 and 21.7 GHz). The flux densities were measured at several epochs. A six-frequency broadband radio spectrum was obtained by observing simultaneously with an accuracy of up to a minute at 1.4, 2.7, 3.9, 6.25, 13, and 30 cm. Results. The original GPS source samples were highly contaminated. Finally, we selected 29% GPS source candidates within the sample. We found some difference in spectral properties between GPS galaxies and quasars within the sample. The GPS galaxies demonstrate a steeper spectral index in the optically thin part of the spectra. There are only relatively few (17) sources whose radio spectra strictly agree with the spectra of homogeneous self-absorbed synchrotron sources. The narrowest radio spectra are found in both ultra-high-z (z ≥ 1.8) and low-z (0.02 ≤ z ≤ 0.7, FWHM ∼ 0.9) convex spectrum radio sources. The majority of quasars within this sample should be considered as flat-spectrum radio sources with a temporarily inverted spectrum, and not as genuine GPS sources. The number of truly convex-spectrum sources remains low, and the lists of GPS sources should accordingly be revised.

Radio properties of Compact Steep Spectrum and GHz‐Peaked Spectrum radio sources

“…In particular, high fraction of CSS radio galaxies are not variable, while only ∼30% of GPS/HFP galaxies preserve the convex spectrum (Torniainen et al 2007, Hancock et al 2010. The majority of the CSS, GPS, and HFP quasars show significant flux density and spectral variability (Mingaliev et al 2012, Orienti et al 2007). Spectral changing and flux density variability do not always imply that the source is part of the blazar population, rather than a genuine CSS/GPS/HFP object.…”

Radio spectra of bright compact sources at z>4.5

“…As the 1.4 GHz NVSS and 325 MHz WENSS images show that the nearest neighbour is at a distance of 232 arcsec from J1606+3124 and based on the probabilities of the sources 6 http://third.ucllnl.org/cgi-bin/firstcutout being side lobes, we conclude that the five neighbouring sources in the 1.4 GHz FIRST image are all image artefacts. We matched J1606+3124 to sources in the 0.96, 2.3, 3.9, 7.7, 11.2 and 21.65 GHz catalogues of Kovalev et al (1999) and the 1.1, 2.3, 4.8, 7.7, 11.2 and 21.7 GHz catalogues of Mingaliev et al (2012). However, since these observations were taken with the RATAN-600 telescope, the resolution of all of the observations is lower than the distance to the nearest neighboring source.…”

“…From this they concluded that J1606+3124 is not variable. While we discarded the matches to Mingaliev et al (2012), we note that the authors did observe J1606+3124 six times with the RATAN-600 telescope between 2006 July and 2010 May at 21.7, 11.2, 7.7, 4.8 and 2.3 GHz, and five times at 1 GHz over the same period. These observations also indicate that J1606+3124 is not variable at these frequencies.…”

Simultaneous spectra and radio properties of BL Lacs

“…The experimental data were processed using the modules of the FADPS (Flexible Astronomical Data Processing System) standard reduction package by Verkhodanov (); this is a reduction system for data from the broadband continuum radiometers of the RATAN‐600 secondary mirror. The processing methods are described in Mingaliev et al () (). The following eight flux density calibrators were used to calculate the calibration coefficients in the scale by Baars et al (): 3C48, 3C138, 3C147, 3C161, 3C286, 3C295, 3C309.1, and NGC 7027.…”