Parsec-scale properties of eight Fanaroff-Riley type 0 radio galaxies

Abstract

We report the high-resolution radio observations of eight Fanaroff-Riley type 0 radio galaxies (FR 0s), selected from the published FR 0 sample. These observations were carried out with the Very Long Baseline Array (VLBA) and European VLBI Network (EVN) at frequencies of 5 and 8 GHz with a highest resolution of ∼0.6 milliarcsec. All eight sources show compact structures on projected physical sizes of 0.3-10 parsec. Six sources show a two-sided structure and two sources show a one-sided jet structure. J1025+1022 shows an X-shaped jet structure, which could result from a reorientation of the jet axis due to a restart of the central engine or a projection of a highly curved inner jet. However, more studies are needed to examine these scenarios. Proper motions for 22 jet components of the eight sources are determined to be between -0.08c and 0.51c. Although most of the sources exhibit flat spectra, other observed characteristics, such as low-amplitude flux density variations, low jet proper motion speeds and symmetric two-sided jet structures, tend to support the fact that the parsec-scale FR 0 jets are mildly relativistic with lower bulk Lorentz factors and larger viewing angles.