Progress has been made in the study of high redshift radio galaxies

2022-06-24 0 By

An Tao, a researcher at the Shanghai Astronomical Observatories of the Chinese Academy of Sciences, led an international team of researchers using Very Long Baseline InterferometryFIRST J160608.5+312446 (J1606+3124 for short) is a compact symmetric source (CSO).In other words, it is a young radio source, a large two-lobe radio source in its infancy.Phase high redshift radio galaxies (HzRG, Z > 4.5) are the most massive galaxies in the universe. The higher the redshift is, the closer it is to the early form of the universe.The study of high redshift radio galaxies helps to reveal the activity of active galactic nuclei (AGNs) in massive elliptical galaxies and the formation and evolution of galaxy clusters in the universe.AGN near the end of cosmic reionization is an important target for studying the trigger mechanism of black hole activity in the early universe and the feedback of jets to the host galaxy environment.For a long time, the technical challenge of searching for high redshift active galactic nuclei is that it is difficult to obtain the spectral redshift of high redshift objects.In the host galaxies of high redshift AGNs, large amounts of gas and dust mask the radiation from the central active galactic nucleus, making observations very difficult, resulting in only a few high redshift radio galaxies being observed.The study used VLBI technology to observe the high-redshift radio galaxy J1606+3124.VLBI technology uses radio waves that are not obscured by dust, can detect the nuclei of distant AGNs, and can image radio jets with milliarcsecond resolution, which is crucial for studying AGN activity and jet feedback.The team obtained high-resolution images of J1606+3124 at 8.4GHz — a “strip” radio structure 220 light-years in size that can be divided into three components along the north-south direction.The radio characteristics of the J1606+3124 include an edge brightening pattern, a peak radio spectrum at the GHz frequency, slow light variability, and low jet velocity.Judging from the size of its radio structure and the expansion rate of the two hot spots, J1606+3124 is a young radio source with a kinematic age of about 3600 years.All these characteristics are consistent with the definition of compact symmetric source.Therefore, the team considers J1606+3124 to be a CSO object.Combined with infrared observation data, the team found that J1606 + 3124 in a gas and dust are very rich environment, the main galaxy on the surrounding dense interstellar medium may hinder the growth of the jet, making it flow in with the surrounding interstellar medium lost part of the kinetic energy of the collision, and translated into radiation, make it a bright radio source.The high radio luminosity and mild relativistic jets of J1606+3124 can be observed even in the presence of large gas barriers in the host galaxy.If its black hole activity continues for a long time, it still has a chance to grow into a large, two-lobe radio galaxy.If its redshift and galaxy classification can be confirmed by further optical spectroscopic observations, J1606+3124 will be the CSO galaxy with the highest redshift known to date.The results are in the Monthly Notices of the Royal Astronomical Society.Very long Baseline array image of J1606+3124 at 8.4 GHz source: Shanghai Astronomical Observatories, Chinese Academy of Sciences