Emission Modeling in the EHT–ngEHT Age

Anantua, Richard; Joaquín, Dúran,; Ngata, Nathan; Oramas, Lani; Röder, Jan; Emami, Razieh; Ricarte, Angelo; Curd, Brandon; Broderick, Avery E.; Wayland, Jeremy; Wong, George N.; Ressler, Sean M.; Nigam, Nitya; Durodola, Emmanuel

doi:10.3390/galaxies11010004

Cited by 3 publications

(1 citation statement)

References 83 publications

(111 reference statements)

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“…We emphasize that the polarization maps here use the standard EHT point spread function based on a 20 µ as beam. However, ngEHT may be able to focus on half this scale, In [48], intensity maps are shown to possess higher maxima when they are more highly resolved owing to an increase in pixels per plane. The effect of partitioning the intensity into refined bins can also slightly shift the location of intensity maxima.…”

Section: Polarized Imagesmentioning

confidence: 99%

Probing Plasma Composition with the Next Generation Event Horizon Telescope (ngEHT)

et al. 2023

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We explore the plasma matter content in the innermost accretion disk/jet in M87* as relevant for an enthusiastic search for the signatures of anti-matter in the next generation of the Event Horizon Telescope (ngEHT). We model the impact of non-zero positron-to-electron ratio using different emission models, including a constant electron to magnetic pressure (constant βe model) with a population of non-thermal electrons as well as an R-beta model populated with thermal electrons. In the former case, we pick a semi-analytic fit to the force-free region of a general relativistic magnetohydrodynamic (GRMHD) simulation, while in the latter case, we analyze the GRMHD simulations directly. In both cases, positrons are being added at the post-processing level. We generate polarized images and spectra for some of these models and find out that at the radio frequencies, both of the linear and the circular polarizations are enhanced with every pair added. On the contrary, we show that, at higher frequencies, a substantial positron fraction washes out the circular polarization. We report strong degeneracies between different emission models and the positron fraction, though our non-thermal models show more sensitivities to the pair fraction than the thermal models. We conclude that a large theoretical image library is indeed required to fully understand the trends probed in this study, and to place them in the context of a large set of parameters which also affect polarimetric images, such as magnetic field strength, black hole spin, and detailed aspects of the electron temperature and the distribution function.

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Section: Polarized Imagesmentioning

confidence: 99%

Probing Plasma Composition with the Next Generation Event Horizon Telescope (ngEHT)

et al. 2023

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On the comparison of AGN with GRMHD simulations – II. M87

Anantua,

Ricarte,

Wong

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Horizon-scale observations of the jetted active galactic nucleus M87 are compared with simulations spanning a broad range of dissipation mechanisms and plasma content in three-dimensional general relativistic flows around spinning black holes. Observations of synchrotron radiation from radio to X-ray frequencies can be compared with simulations by adding prescriptions specifying the relativistic electron-plus-positron distribution function and associated radiative transfer coefficients. A suite of time-varying simulations with various spins, plasma magnetizations and turbulent heating and equipartition-based emission prescriptions (and piecewise combinations thereof) is chosen to represent distinct possibilities for the M87 jet/accretion flow/black hole (JAB) system. Simulation jet morphology, polarization and variation are then ‘observed’ and compared with real observations to infer the rules that govern the polarized emissivity. Our models support several possible spin/emission model/plasma composition combinations supplying the jet in M87, whose black hole shadow has been observed down to the photon ring at 230 GHz by the Event Horizon Telescope (EHT). Net linear polarization and circular polarization constraints favor magnetically arrested disk (MAD) models whereas resolved linear polarization favors standard and normal evolution (SANE) in our parameter space. We also show that some MAD cases dominated by intrinsic circular polarization have near-linear V/I dependence on un-paired electron or positron content while SANE polarization exhibits markedly greater positron-dependent Faraday effects – future probes of the SANE/MAD dichotomy and plasma content with the EHT. This is the second work in a series also applying the ‘observing’ simulations methodology to near-horizon regions of supermassive black holes in Sgr A* and 3C 279.

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Constraining photon trajectories in black hole shadows

Pugliese,

Stuchlík

2024

Eur. Phys. J. Plus

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We examine the shadow cast by a Kerr black hole, focusing on constraints on photons corresponding to different shadow boundaries. The photons are related to different orbital ranges and impact parameter values, creating a map of the shadow boundaries. Our analysis fixes also the conditions under which it is possible to observe an “imprint” of the black hole (outer) ergosurface and (outer) ergoregion on the Kerr black hole shadow boundary. The counter-rotating case resulted strongly constrained with respect to the co-rotating case, constituting a remarkable and significant difference where the counter-rotating component associated with the shadow boundary is strongly distinct from the co-rotating one. However, in this framework, even the co-rotating photons imply restrictions on conditions on the spins and planes, which are bounded by limiting values. We believe the results found here, being a tracer for the central black hole, can constitute new templates for the ongoing observations.

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Emission Modeling in the EHT–ngEHT Age

Cited by 3 publications

References 83 publications

Probing Plasma Composition with the Next Generation Event Horizon Telescope (ngEHT)

Probing Plasma Composition with the Next Generation Event Horizon Telescope (ngEHT)

On the comparison of AGN with GRMHD simulations – II. M87

Constraining photon trajectories in black hole shadows

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