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

分类： 天文学 >> 天文学 提交时间： 2023-02-19

Guang-Yao Zhao Jose L. Gomez Antonio Fuentes Thomas P. Krichbaum E. Traianou Rocco Lico Ilje Cho Eduardo Ros S. Komossa Kazunori Akiyama Keiichi Asada Lindy Blackburn Silke Britzen Gabriele Bruni Geoffrey Crew Rohan Dahale Lankeswar Dey Roman Gold Achamveedu Gopakumar Sara Issaoun

摘要： We present the first very-long-baseline interferometric (VLBI) observations of the blazar OJ287 carried out jointly with the Global Millimeter VLBI Array (GMVA) and the phased Atacama Large Millimeter/submillimeter Array (ALMA) at 3.5 mm on April 2, 2017. Participation of phased-ALMA not only has improved the GMVA north-south resolution by a factor of ~3, but also has enabled fringe detection with signal-to-noise ratios up to 300 at baselines longer than 2 G{\lambda}. The high sensitivity has motivated us to image the data with the 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 {\mu}as that resembles 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 {\mu}as 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.

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