Physical conditions in faint gigahertz-peaked spectrum radio sources

Abstract

Weak, compact radio sources (∼100 mJy peak flux, L∼1–10 pc) with their spectral peaks at about a gigahertz are studied, based on the complete sample of 46 radio sources of Snellen, drawn from high-sensitivity surveys, including the low-frequency Westerbork catalog. The physical parameters have been estimated for 14 sources: the magnetic field (H⊥), the number density of relativistic particles (ne), the energy of the magnetic field \((E_{H_ \bot } )\), and the energy of relativistic particles (Ee). Ten sources have \(E_{H_ \bot } \ll E_e \), three have approximate equipartition of the energies \((E_{H_ \bot } \sim E_e )\), and only one has \(E_{H_ \bot } \gg E_e \). The mean magnetic fields in quasars (10−3 G) and galaxies (10−2 G) have been estimated. The magnetic field appears to be related to the sizes of compact features as \(H \sim 1/\sqrt L \).