Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. V. Space and Ground Millimeter-VLBI Imaging of OJ 287

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Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2022-01
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Language
en
Pages
16
Series
Astrophysical Journal, Volume 924, issue 2
Abstract
We present the first polarimetric space very long baseline interferometry (VLBI) observations of OJ 287, observed with RadioAstron at 22 GHz during a perigee session on 2014 April 4 and five near-in-time snapshots, together with contemporaneous ground VLBI observations at 15, 43, and 86 GHz. Ground-space fringes were obtained up to a projected baseline of 3.9 Earth diameters during the perigee session, and at a record 15.1 Earth diameters during the snapshot sessions, allowing us to image the innermost jet at an angular resolution of ∼50μ as, the highest ever achieved at 22 GHz for OJ 287. Comparison with ground-based VLBI observations reveals a progressive jet bending with increasing angular resolution that agrees with predictions from a supermassive binary black hole model, although other models cannot be ruled out. Spectral analyses suggest that the VLBI core is dominated by the internal energy of the emitting particles during the onset of a multiwavelength flare, while the parsec-scale jet is consistent with being in equipartition between the particles and magnetic field. Estimated minimum brightness temperatures from the visibility amplitudes show a continued rising trend with projected baseline length up to 1013 K, reconciled with the inverse-Compton limit through Doppler boosting for a jet closely oriented to the line of sight. The observed electric vector position angle suggests that the innermost jet has a predominantly toroidal magnetic field, which, together with marginal evidence of a gradient in rotation measure across the jet width, indicates that the VLBI core is threaded by a helical magnetic field, in agreement with jet formation models.
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Funding Information: Original content from this work may be used under the terms of the . Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Spanish Ministerio de Economia y Competitividad AYA2016-80889-P Spanish Ministerio de Economia y Competitividad PID2019-108995GB-C21 Consejeria de Economia, Conocimiento, Empresas y Universidad of the Junta de Andalucia P18-FR-1769 Consejo Superior de Investigaciones Cientificas 2019AEP112 State Agency for Research of the Spanish MCIU through the Center of Excellence Severo Ochoa award for the Instituto de Astrofisica de Andalucia SEV-2017-0709 yes � 2022. The Author(s). Published by the American Astronomical Society. Creative Commons Attribution 4.0 licence Publisher Copyright: © 2022. The Author(s). Published by the American Astronomical Society.
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Gómez, J L, Traianou, E, Krichbaum, T P, Lobanov, A P, Fuentes, A, Lico, R, Zhao, G-Y, Bruni, G, Kovalev, Y Y, Lähteenmäki, A, Voitsik, P A, Lisakov, M M, Angelakis, E, Bach, U, Casadio, C, Cho, I, Dey, L, Gopakumar, A, Gurvits, L I, Jorstad, S, Kovalev, Y A, Lister, M L, Marscher, A P, Myserlis, I, Pushkarev, A B, Ros, E, Savolainen, T, Tornikoski, M, Valtonen, M J & Zensus, A 2022, ' Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. V. Space and Ground Millimeter-VLBI Imaging of OJ 287 ', The Astrophysical Journal, vol. 924, no. 2, 122 . https://doi.org/10.3847/1538-4357/ac3bcc