Jet Properties of Compact Steep-spectrum Sources and an Eddington-ratio-driven Unification Scheme of Jet Radiation in Active Galactic Nuclei

Abstract

Abstract Compact steep-spectrum sources (CSSs) likely represent a population of young radio-loud active galactic nuclei (AGNs) and have been identified as γ-ray-emitting sources. We present a comprehensive analysis of their γ-ray emission observed with Fermi/LAT and establish their broadband spectral energy distributions (SEDs). We derive their jet properties using SED fits with a two-zone leptonic model for radiation from the compact core and the large-scale extended region, and explore the possible signature of a unification picture of jet radiation among subclasses of AGNs. We show that the observed γ-rays of CSSs with significant variability are contributed by the radiation of their compact cores via the inverse-Compton process of the torus photons. The derived power-law distribution index of the radiating electrons is p 1 ∼ 1.5–1.8, magnetic field strength is B ∼ 0.15–0.6 G, and Doppler-boosting factor is δ ∼ 2.8–8.9. Assuming that the jet is composed of e ± pairs, the compact cores of CSSs are magnetized and have a high radiation efficiency, similar to that of flat-spectrum radio quasars. The γ-ray-emitting CSSs on average have higher Eddington ratio and black hole mass than those non-GeV-detected CSSs, and they follow the correlation between the jet power in units of Eddington luminosity ( ) and Eddington ratio (R Edd) with other subclasses of AGNs, , indicating that R Edd would be a key physical driver for the unification scheme of AGN jet radiation.