The relationship between FR0 radio galaxies and gigahertz‐peaked spectrum sources

Abstract

AbstractWe present the results of our study of the relationship between Fanaroff‐Riley type 0 (FR0) radio galaxies and gigahertz‐peaked spectrum (GPS) sources. Quasi‐simultaneous radio spectra of 34 FR0s were obtained at 2.25–22.3 GHz with the radio telescope RATAN‐600 in 2020–2021 during 2–6 epochs. Most FR0s have flat radio spectra, but we found many spectra with a peaked shape. Due to this fact and the compact nature of FR0s, we suggest their possible relationship with compact steep‐spectrum (CSS)/GPS radio sources. We analyzed broadband radio spectra of the 34 FR0s using the RATAN‐600 measurements and available literature data. There are 14 FR0 objects which can be CSS/GPS radio source candidates. Most FR0s have broader radio spectra than those of genuine GPS sources, with like in blazars. Most spectral indices at the frequencies below and above the peak do not correspond to the values typical of canonical GPS sources. We classified 3 FR0s as low‐power GPS sources according to the canonical criteria. The key issue is the variability properties of FR0s. Some FR0s demonstrate a variability level of up to 25% on a time scale of 1 year according to the RATAN‐600 measurements. The flare phenomena in FR0 objects can imply a relationship between them and blazars.