Multifrequency study of gigahertz‐peaked spectrum sources with RATAN‐600

Abstract

We report the radio continuum properties for several samples of peaked spectrum (PS) radio sources. Broadband spectra of the objects were analyzed using the RATAN‐600 six‐frequency (1.2–22 GHz) observations and available literature data, obtained on a time scale of 20–30 years. We discuss statistical differences in radio properties for several AGN types with peaked spectra and focus on PS quasars at high redshifts (z>3). We confirm that a relatively small fraction (1–2%) of bright PS sources can be considered genuine gigahertz‐peaked spectrums (GPSs) when they have been monitored densely and for a long time. The contamination of GPS source samples by blazars is getting stronger as the redshift increases, and we confirm that it is underestimated due to lack of systematic multifrequency observations.

High-Redshift Quasars at z ≥ 3: Radio Variability and MPS/GPS Candidates

“…Blazars have the potential to contaminate GPS source samples since they exhibit peaked radio spectra during their flaring states [38,40,108,109]. In this section, we focus on the broadband long-term radio spectra of 23 quasars previously classified as HFP, GPS, or MPS sources [21,32,36,106,[110][111][112][113][114].…”

“…This expansion usually does not change the shape of the spectrum, although the peak frequency might shift [39]. In contrast, blazars exhibit strong and rapid flux variations in a wide range of timescales and frequencies, often accompanied by changes in the spectrum shape, such as a peaked spectrum during flaring activity (e.g., [38,40,41]). By classifying GPS/MPS sources and blazars among high-redshift radio sources, we can gain insights into the underlying physical mechanisms that govern their formation and evolution, which may have profound implications for our understanding of the early Universe.…”

High–Redshift Quasars at <em>z </em><span data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>z</mi><mo>&#x2265;</mo><mn>3</mn></math>">≥ 3: Radio Variability and MPS/GPS Candidates

“…Blazars have the potential to contaminate GPS source samples since they exhibit peaked radio spectra during their flaring states [39,41,107,108]. In this section, we focus on the broadband long-term radio spectra of 23 quasars previously classified as HFP, GPS, or MPS sources [21,33,37,105,[109][110][111][112][113].…”

“…Variability serves as an important indicator to distinguish between blazars and unbeamed PS sources. Genuine GPS sources exhibit low levels of variability (e.g., [32][33][34][35][36][37][38][39]), which may be attributed to the expansion of the compact lobes. This expansion usually does not change the shape of the spectrum, although the peak frequency might shift [40].…”

“…This expansion usually does not change the shape of the spectrum, although the peak frequency might shift [40]. In contrast, blazars exhibit strong and rapid flux variations in a wide range of timescales and frequencies, often accompanied by changes in the spectrum shape, such as a peaked spectrum during flaring activity (e.g., [39,41,42]). By classifying GPS/MPS sources and blazars among high-redshift radio sources, we can gain insights into the underlying physical mechanisms that govern their formation and evolution, which may have profound implications for our understanding of the early Universe.…”