Multifrequency Study of GHz-peaked Spectrum Sources

Abstract

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. The catalog containing spectral flux densities measured at six frequencies (1.1, 2.3, 4.8, 7.7/8.2, 11.2, and 21.7 GHz) have been obtained. In addition, for the analysis of radio spectra, data from the following low-frequency surveys have been used: GLEAM (GaLactic and Extragalactic All-sky Murchison widefield array survey) and TGSS (Tata institute for fundamental research GMRT Sky Survey) and high-frequency measurements from Planck survey. A total number of 164 GPS and candidates to GPS 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 AGN types. The deficit of distant GPS (z > 2) with low maximum frequencies (less than 1 GHz) is confirmed. The existing "size -peak frequency" anticorrelation is continuous. The continuum radio spectra are found to become statistically steeper with increasing redshift.

Caltech-NRAO Stripe 82 Survey (CNSS). V. AGNs That Transitioned to Radio-loud State

“…In turn, in the case of quasars, a much faster and a more significant change of their radio spectral properties means that they appear on ν p − l plane only for a short period of time. This is in agreement with previous studies of GPS sources saying that over time, even most quasar-type GPS sources no longer meet the criteria for belonging to this class of objects (Dallacasa et al 2000;Torniainen et al 2005;Orienti & Dallacasa 2012;Sotnikova et al 2019). This behavior prevents many young GPS quasars from being recognized as such, and therefore they may remain hidden in the flat-spectrum quasar population.…”

“…It has been shown based on different samples of radio sources that there is a continuous distribution of young AGNs along the frequency of the peak (turnover frequency) ν p − l linear size plane (O'Dea & Baum 1997;Orienti & Dallacasa 2014;Sotnikova et al 2019). This relationship suggests that the physical properties of the CSS and GPS sources are similar, and the only variable that depends directly on their size is their turnover frequency.…”

The SPECFIND V3.0 catalog of radio continuum cross-identifications and spectra: Reaching lower frequencies

“…They classified objects with α low ≥ 0.1 and α high > 0.1 as GPS sources. In another recent study, Sotnikova et al (2019) found 164 GPS sources based on observations of the candidate sample from Mingaliev et al (2013). We compared our results to these two recent studies, by first creating a combined sample of our two spectral break samples.…”

Caltech-NRAO Stripe 82 Survey (CNSS). IV. The Birth of Radio-loud Quasar 013815+00

“…There is a continuous distribution of these objects across the ν p −l plane, which suggest that GPS and CSS sources are scaled versions of each other. However, the long-term monitoring of samples of GPS sources lasting 10-20 years shows that with time even the majority of them cease to adhere to the generic GPS source properties (Dallacasa et al 2000;Torniainen et al 2005;Orienti et al 2006;Sotnikova et al 2019). This may be due to the fact that the GPS phase occurs in many, or even all, populations of radio sources and is what at the initial stage of development connects them with each other.…”