分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： 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 mas. 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, but more studies are needed to examine these scenarios. Proper motions for 22 jet components of the eight sources are determined to be between -0.08 c and 0.51 c. 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 that the pc-scale FR 0 jets are mildly relativistic with lower bulk Lorentz factors and larger viewing angles.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Studies of high redshift radio galaxies can shed light on the activity of active galactic nuclei (AGN) in massive elliptical galaxies, and on the assembly and evolution of galaxy clusters in the Universe. J1606+3124 has been tentatively identified as a radio galaxy at a redshift of 4.56, at an era of one-tenth of the current age of the Universe. Very long baseline interferometry (VLBI) images show a compact triple structure with a size of 68 parsecs. The radio properties of J1606+3124, including the edge-brightening morphology, peaked GHz radio spectrum, slow variability, and low jet speed, consistently indicate that it is a compact symmetric object (CSO). The radio source size and expansion rate of the hotspots suggest that J1606+3124 is a young (kinematic age of ~3600 years) radio source. Infrared observations reveal a gas- and dust-rich host galaxy environment, which may hinder the growth of the jet; however, the ultra-high jet power of J1606+3124 gives it an excellent chance to grow into a large-scale double-lobe radio galaxy. If its redshift and galaxy classification can be confirmed by further optical spectroscopic observations, J1606+3124 will be the highest redshift CSO galaxy known to date.
点击量
待评议
点击量
下载量
评论
