Compact Symmetric Objects. III. Evolution of the High-luminosity Branch and a Possible Connection with Tidal Disruption Events

We use a sample of 54 compact symmetric objects (CSOs) to confirm that there are two unrelated CSO classes: an edge-dimmed, low-luminosity class (CSO 1), and an edge-brightened, high-luminosity class (CSO 2). Using blind tests, we show that CSO 2s consist of three subclasses: CSO 2.0, having prominent hot spots at the leading edges of narrow jets and/or narrow lobes; CSO 2.2, without prominent hot spots and with broad jets and/or lobes; and CSO 2.1, which exhibit mixed properties. Most CSO 2s do not evolve into larger jetted active galactic nuclei (AGN), but spend their whole life cycle as CSOs of size ≲500 pc and age ≲5000 yr. The minimum energies needed to produce the radio luminosity and structure in CSO 2s range from ∼10⁻⁴M_⊙c² to ∼7 M_⊙c². We show that the transient nature of most CSO 2s, and their birth rate, can be explained through ignition in the tidal disruption events of stars. We also consider possibilities of tapping the spin energy of the supermassive black hole, and tapping the energy of the accretion disk. Our results demonstrate that CSOs constitute a large family of AGN in which we have thus far studied only the brightest. More comprehensive CSO studies, with higher sensitivity, resolution, and dynamic range, will revolutionize our understanding of AGN and the central engines that power them.

We thank Martin Rees for discussions that led to a significant improvement in our interpretation of these results. We thank Christopher O'Dea for providing the data on the large-scale structure of 0108+388. We thank the reviewer of this paper for many helpful suggestions that have clarified several important aspects of this work. This research has made use of data from the MOJAVE database that is maintained by the MOJAVE team (Lister et al. 2018). The MOJAVE program is supported by NASA-Fermi grant 80NSSC19K1579. S.K. and K.T. acknowledge support from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program under grant agreement No. 771282. K.T. acknowledges support from the Foundation of Research and Technology—Hellas Synergy Grants Program through project POLAR, jointly implemented by the Institute of Astrophysics and the Institute of Computer Science. A.S. acknowledges support from the NASA contract NAS8-03060 (Chandra X-ray Center). G.T. and E.S. acknowledge support from NSF Grant AST-1835400. N.G.'s research is supported by the Simons Foundation, the Chancellor Fellowship at UCSC, and the Vera Rubin Presidential Chair.

This paper depended on a very large amount of VLBI data, almost all of which was taken with the Very Long Baseline Array. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

In recognition of his many important contributions to astrophysics and cosmology, and in particular of his work on jetted AGN, this paper is dedicated to Mark Birkinshaw. Mark was working hard on this paper right up until his death from cancer on 2023 July 23. Mark is sorely missed worldwide by his colleagues and friends.