Observable Emission Features of Black Hole GRMHD Jets on Event Horizon Scales

Pu, Hung-Yi; Wu, Kinwah; Younsi, Ziri; Asada, Keiichi; Mizuno, Yosuke; Nakamura, Masanori

doi:10.3847/1538-4357/aa8136

Cited by 18 publications

(18 citation statements)

References 86 publications

(100 reference statements)

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“…Similarly, were the apparent ring a random alignment of emission blobs, they should also have moved away at relativistic speeds, i.e., at ∼5 μas day −1 (Kim et al 2018b), leading to measurable structural changes and sizes. GRMHD models of hollow jet cones could show under extreme conditions stable ring features (Pu et al 2017), but this effect is included to a certain extent in our Simulation Library for models with R high >10. Finally, an Einstein ring formed by gravitational lensing of a bright region in the counter-jet would require a fine-tuned alignment and a size larger than that measured in 2012 and 2009.…”

Section: Discussionmentioning

confidence: 99%

First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole

Akiyama¹,

Alberdi²,

Alef³

et al. 2019

ApJL

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When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42±3 μas, which is circular and encompasses a central depression in brightness with a flux ratio 10:1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and width remaining stable over four different observations carried out in different days. Overall, the observed image is consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic magnetohydrodynamic simulations of black holes and derive a central mass of M=(6.5±0.7)×10 9 M e . Our radiowave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible.

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Section: Discussionmentioning

confidence: 99%

First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole

Akiyama¹,

Alberdi²,

Alef³

et al. 2019

ApJL

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3,022

1,428

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“…For example, it is possible to study simplified, phenomenological models. Emission features due to the cooling of nonthermal electrons may then reveal how and where the nonthermal electrons are produced (Pu et al 2017). Emission features created by the injection of nonthermal electrons within GRMHD models of the jet and their subsequent cooling will be studied separately (T. Kawashima et al 2019, in preparation).…”

Section: Nonthermal Electronsmentioning

confidence: 99%

First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring

Akiyama¹,

Alberdi²,

Alef³

et al. 2019

ApJL

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The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. To this end, we construct a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by general relativistic ray tracing. We compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. The ring radius and ring asymmetry depend on black hole mass and spin, respectively, and both are therefore expected to be stable when observed in future EHT campaigns. Overall, the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity. If the black hole spin and M87's large scale jet are aligned, then the black hole spin vector is pointed away from Earth. Models in our library of non-spinning black holes are inconsistent with the observations as they do not produce sufficiently powerful jets. At the same time, in those models that produce a sufficiently powerful jet, the latter is powered by extraction of black hole spin energy through mechanisms akin to the Blandford-Znajek process. We briefly consider alternatives to a black hole for the central compact object. Analysis of existing EHT polarization data and data taken simultaneously at other wavelengths will soon enable new tests of the GRMHD models, as will future EHT campaigns at 230 and 345 GHz.

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“…The observed continuous jet collimation profile from the vicinity of the jet base to the distance of 200,000 r s (Junor et al 1999;Doeleman et al 2012;Asada & Nakamura 2012;Hada et al 2013) implies that a similar mechanism of jet collimation by the winds may be at work on smaller scales as well. On-going and future full-polarimetric observations with the EHT (e.g., Doeleman et al 2008Doeleman et al , 2012Lu et al 2013;Akiyama et al 2015;Johnson et al 2015Johnson et al , 2018Fish et al 2016;Lu et al 2018) in conjunction with the phased-up ALMA at 230 and 345 GHz will provide an unprecedented view of polarization and RM structures in the jet on scales down to a few r s together with an image of the black hole shadow (e.g., Broderick & Loeb 2009;Dexter et al 2012;Lu et al 2018;Chael et al 2016;Mościbrodzka et al 2016Mościbrodzka et al , 2017Akiyama et al 2017;Pu et al 2017), enabling a definitive test for the origin of winds and the jet.…”

Section: Eht Observationsmentioning

confidence: 99%

Faraday Rotation in the Jet of M87 inside the Bondi Radius: Indication of Winds from Hot Accretion Flows Confining the Relativistic Jet

Park

Hada

Kino

et al. 2019

ApJ

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We study Faraday rotation in the jet of M87 inside the Bondi radius using eight Very Long Baseline Array data sets, one at 8 GHz, four at 5 GHz, and three at 2 GHz. We obtain Faraday rotation measures (RMs) measured across the bandwidth of each data set. We find that the magnitude of RM systematically decreases with increasing distance from the black hole from 5,000 to 200,000 Schwarzschild radii. The data, showing predominantly negative RM sign without significant difference of the RMs on the northern and southern jet edges, suggest that the spatial extent of the Faraday screen is much larger than the jet. We apply models of hot accretion flows, thought to be prevalent in active galactic nuclei having relatively low luminosity such as M87, and find that the decrease of RM is described well by a gas density profile ρ ∝ r −1 . This behavior matches the theoretically expected signature of substantial winds, nonrelativistic un-collimated gas outflows from hot accretion flows, which is consistent with the results of various numerical simulations. The pressure profile inferred from the density profile is flat enough to collimate the jet, which can result in gradual acceleration of the jet in a magneto-hydrodynamical process. This picture is in good agreement with the observed gradual collimation and acceleration of the M87 jet inside the Bondi radius. The dominance of negative RMs suggests that jet and wind axis are misaligned such that the jet emission exposes only one side of the toroidal magnetic fields permeating the winds.

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Observable Emission Features of Black Hole GRMHD Jets on Event Horizon Scales

Cited by 18 publications

References 86 publications

First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole

First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole

First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring

Faraday Rotation in the Jet of M87 inside the Bondi Radius: Indication of Winds from Hot Accretion Flows Confining the Relativistic Jet

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