The limb-brightened jet of M87 down to the 7 Schwarzschild radii scale

By Jae-Young Kim, T. Krichbaum, R. Lu, E. Ros, U. Bach, M. Bremer, P. Vicente, Michael Lindqvist, J. Zensus. Astronomy & Astrophysics, 2018

146 citations recorded by the source corpus.

Messier 87 (M 87) is one of the nearest radio galaxies with a prominent jet extending from sub-pc to kpc scales. Because of its proximity and the large mass of its central black hole (BH), it is one of the best radio sources for the study of jet formation. We study the physical conditions near the jet base at projected separations from the BH of ~7–100 Schwarzschild radii (Rsch). Global mm-VLBI Array (GMVA) observations at 86 GHz (λ = 3.5 mm) provide an angular resolution of ~50 μas, which corresponds to a spatial resolution of only 7 Rsch and reach the small spatial scale. We use five GMVA data sets of M 87 obtained from 2004 to 2015 and present new high angular resolution VLBI maps at 86 GHz. In particular, we focus on the analysis of the brightness temperature, the jet ridge lines, and the ratio of jet to counter-jet. The imaging reveals a parabolically expanding limb-brightened jet which emanates from a resolved VLBI core of ~(8–13) Rsch in size. The observed brightness temperature of the core at any epoch is ~(1–3) × 1010 K, which is below the equipartition brightness temperature and suggests magnetic energy dominance at the jet base. We estimate the diameter of the jet at its base to be ~5 Rsch assuming a self-similar jet structure. This suggests that the sheath of the jet may be anchored in the very inner portion of the accretion disk. The image stacking reveals faint emission at the center of the edge-brightened jet on sub-pc scales. We discuss its physical implication within the context of the spine-sheath structure of the jet.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/bc53adfd3021214b4cbed0301a88865374f1760f

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Citations in the corpus

First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring (2019, unknown): “…2012; Hada et al. 2013; Nakamura et al. 2018), the total jet power at kilo-parsec scale (Owen et al. 2000; Stawarz et al. 2006), the jet power (e.g., Kino et al. 2014, 2015), the core shift (Hada et al. 2011), and the symmetric limb-brightening structure (Takahashi et al. 2018; Kim et al. 2018).”
Magnetic Reconnection and Hot Spot Formation in Black Hole Accretion Disks (2020, background): “…close to the event horizon can potentially explain Very Long Baseline Interferometry (VLBI) observations of the black hole at the center of the galaxy M87 which clearly show a limb-brightened jet down to 7rg (Ly et al. 2007; Kovalev et al. 2007; Hada et al. 2016; Kim et al. 2016; Kim et al. 2018).”