RadioAstron discovery of a mini-cocoon around the restarted parsec-scale jet in 3C 84
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Astronomy & Astrophysics, Volume 676
Abstract
We present RadioAstron space-based very long baseline interferometry (VLBI) observations of the nearby radio galaxy 3C 84 (NGC 1275) at the centre of the Perseus cluster. The observations were carried out during a perigee passage of the Spektr-R spacecraft on September 21a-22, 2013 and involved a global array of 24 ground radio telescopes observing at 5 GHz and 22 GHz, together with the Space Radio Telescope (SRT). Furthermore, the Very Long Baseline Array (VLBA) and the phased Very Large Array (VLA) observed the source quasi-simultaneously at 15 GHz and 43 GHz. Fringes between the ground array and the SRT were detected on baseline lengths up to 8.1 times the Eartha-s diameter, providing unprecedented resolution for 3C 84 at these wavelengths. We note that the corresponding fringe spacing is 125 μas at 5 GHz and 27 μas at 22 GHz. Our space-VLBI images reveal a previously unseen sub-structure inside the compact âà1 pc long jet that was ejected about ten years earlier. In the 5 GHz image, we detected, for the first time, low-intensity emission from a cocoon-like structure around the restarted jet. Our results suggest that the increased power of the young jet is inflating a bubble of hot plasma as it carves its way through the ambient medium of the central region of the galaxy. Here, we estimate the minimum energy stored in the mini-cocoon, along with its pressure, volume, expansion speed, and the ratio of heavy particles to relativistic electrons, as well as the density of the ambient medium. About half of the energy delivered by the jet is dumped into the mini-cocoon and the quasi-spherical shape of the bubble suggests that this energy may be transferred to a significantly larger volume of the interstellar medium than what would be accomplished by the well-collimated jet on its own. The pressure of the hot mini-cocoon also provides a natural explanation for the almost cylindrical jet profile seen in the 22 GHz RadioAstron image.Description
Funding Information: We thank Eduardo Ros for a careful reading of the manuscript and valuable comments. We also thank the anonymous referee for constructive criticism that helped us to improve the presentation of the results. The RadioAstron project is led by the Astro Space Center of the Lebedev Physical Institute of the Russian Academy of Sciences and the Lavochkin Scientific and Production Association under a contract with the State Space Corporation ROSCOSMOS, in collaboration with partner organisations in Russia and other countries. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The European VLBI Network is a joint facility of independent European, African, Asian, and North American radio astronomy institutes. This research is based on observations correlated at the Bonn Correlator, jointly operated by the Max Planck Institute for Radio Astronomy (MPIfR), and the Federal Agency for Cartography and Geodesy (BKG). TS was supported by the Academy of Finland projects 274477, 284495, 312496, and 315721. YYK, AVP, and PAV were supported by the Russian Science Foundation grant 21-12-00241. Computer simulations have been carried out in Tirant, the local supercomputer and at the Servei d’Informàtica de la Universitat de València. MP acknowledges support by the Spanish Ministry of Science through Grants PID2019-105510GB-C31, PID2019-107427GB-C33, and from the Generalitat Valenciana through grant PROMETEU/2019/071. JLM acknowledges the support of a fellowship from ‘La Caixa’ Foundation (ID 100010434). The fellowship code is LCF/BQ/DR19/11740030. BWS is grateful for the support by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (MSIT) of Korea (NRF-2020K1A3A1A78114060). Publisher Copyright: © 2023 EDP Sciences. All rights reserved.
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Savolainen, T, Giovannini, G, Kovalev, Y Y, Perucho, M, Anderson, J M, Bruni, G, Edwards, P G, Fuentes, A, Giroletti, M, Gomez, J L, Hada, K, Lee, S S, Lisakov, M M, Lobanov, A P, Lopez-Miralles, J, Orienti, M, Petrov, L, Plavin, A V, Sohn, B W, Sokolovsky, K V, Voitsik, P A & Zensus, J A 2023, 'RadioAstron discovery of a mini-cocoon around the restarted parsec-scale jet in 3C 84', Astronomy & Astrophysics, vol. 676, A114. https://doi.org/10.1051/0004-6361/202142594