Unraveling the Innermost Jet Structure of OJ 287 with the First GMVA + ALMA Observations

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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The Astrophysical Journal, Volume 932, issue 1
We present the first very long baseline interferometric (VLBI) observations of the blazar OJ 287 carried out jointly with the Global Millimeter VLBI Array (GMVA) and the phased Atacama Large Millimeter/submillimeter Array (ALMA) at 3.5 mm on 2017 April 2. The participation of phased ALMA has not only improved the GMVA north-south resolution by a factor of ∼3, but has also enabled fringe detections with signal-to-noise ratios up to 300 at baselines longer than 2 Gλ. The high sensitivity has motivated us to image the data with newly developed regularized maximum likelihood imaging methods, revealing the innermost jet structure with unprecedentedly high angular resolution. Our images reveal a compact and twisted jet extending along the northwest direction, with two bends within the inner 200 μas, resembling a precessing jet in projection. The component at the southeastern end shows a compact morphology and high brightness temperature, and is identified as the VLBI core. An extended jet feature that lies at ∼200 μas northwest of the core shows a conical shape, in both total and linearly polarized intensity, and a bimodal distribution of the linear polarization electric vector position angle. We discuss the nature of this feature by comparing our observations with models and simulations of oblique and recollimation shocks with various magnetic field configurations. Our high-fidelity images also enabled us to search for possible jet features from the secondary supermassive black hole (SMBH) and test the SMBH binary hypothesis proposed for this source.
Funding Information: The work at the IAA-CSIC is supported in part by the Spanish Ministerio de Economía y Competitividad (grants AYA2016-80889-P and PID2019-108995GB-C21), the Consejería de Economía, Conocimiento, Empresas y Universidad of the Junta de Andalucía (grant P18-FR-1769), the Consejo Superior de Investigaciones Científicas (grant 2019AEP112), and the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). This publication acknowledges the project M2FINDERS, which is funded by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 101018682). L.L. acknowledges the support of the DGAPA/PAPIIT grants IN112417 and IN112820, the CONACyT-AEM grant 275201, and the CONACyT-CF grant 263356. T.S. was supported by the Academy of Finland projects 274477, 284495, 312496, and 315721. Y.K. was supported in the framework of the State project “Science” by the Ministry of Science and Higher Education of the Russian Federation, under the contract 075-15-2020-778. J.Y.K acknowledges support from the National Research Foundation of Korea (grant no. 2022R1C1C1005255). R.-S. L is supported by the Max Planck Partner Group of the MPG and the CAS, the Key Program of the National Natural Science Foundation of China (grant No. 11933007), the Key Research Program of Frontier Sciences, CAS (grant No. ZDBS-LY-SLH011), and the Shanghai Pilot Program for Basic Research – Chinese Academy of Science, Shanghai Branch (JCYJ-SHFY-2022-013). Publisher Copyright: © 2022. The Author(s). Published by the American Astronomical Society.
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences
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Zhao, G Y, Gómez, J L, Fuentes, A, Krichbaum, T P, Traianou, E, Lico, R, Cho, I, Ros, E, Komossa, S, Akiyama, K, Asada, K, Blackburn, L, Britzen, S, Bruni, G, Crew, G B, Dahale, R, Dey, L, Gold, R, Gopakumar, A, Issaoun, S, Janssen, M, Jorstad, S, Kim, J Y, Koay, J Y, Kovalev, Y Y, Koyama, S, Lobanov, A P, Loinard, L, Lu, R S, Markoff, S, Marscher, A P, Martí-Vidal, I, Mizuno, Y, Park, J, Savolainen, T & Toscano, T 2022, ' Unraveling the Innermost Jet Structure of OJ 287 with the First GMVA + ALMA Observations ', The Astrophysical Journal, vol. 932, no. 1, 72 . https://doi.org/10.3847/1538-4357/ac6b9c