Blacklight: A General-relativistic Ray-tracing and Analysis Tool

White, Christopher J.

doi:10.3847/1538-4365/ac77ef

Cited by 8 publications

(2 citation statements)

References 51 publications

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“…Some codes also keep track of the electric vector position angle and polarization degree, assuming a geometrically thin equatorial accretion flow (Dovc ˇiak et al 2008, Gelles et al 2021, Cárdenas-Avendaño et al 2023, the latter two being specialized for highly-lensed features by implementing adaptive ray tracing. Only a handful of codes are able of treating the most demanding problem of integrating the full polarized radiative transfer: grtrans (Dexter 2016), ipole (Mościbrodzka and Gammie 2018), Arcmancer (Pihajoki et al 2018), Bhoss (Younsi et al 2020), Raptor (Bronzwaer et al 2020), Blacklight (White 2022), as well as Lemon (Xiao-lin et al 2021) which specializes on polarized radiative transfer with scattering. Some of these polarized GRRT codes were recently compared by Prather et al (2023).…”

Section: Introductionmentioning

confidence: 99%

GYOTO 2.0: a polarized relativistic ray-tracing code

Aimar,

Paumard,

Vincent

et al. 2024

Class. Quantum Grav.

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Polarized general-relativistic radiative transfer in the vicinity of black holes and other compact objects has become a crucial tool for probing the properties of relativistic astrophysics plasmas. Instruments like GRAVITY, the Event Horizon telescope, ALMA, or IXPE make it very timely to develop such numerical frameworks. In this article, we present the polarized extension of the public ray-tracing code \gy, and offer a python notebook allowing to easily perform a first realistic computation. The code is very modular and allows to conveniently add extensions for the specific needs of the user. It is agnostic about the spacetime and can be used for arbitrary compact objects. We demonstrate the validity of the code by providing tests, and show in particular a perfect agreement with the \textsc{ipole} code. Our article also aims at pedagogically introducing all the relevant formalism in a self-contained manner.

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Section: Introductionmentioning

confidence: 99%

GYOTO 2.0: a polarized relativistic ray-tracing code

Aimar,

Paumard,

Vincent

et al. 2024

Class. Quantum Grav.

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“…This is useful for improving analytical results at arbitrary frequency, emission direction with respect to the magnetic field, and distribution function. These works provide fits for the Stokes emissivities, absorptivities, and rotativities that have been widely used in modeling polarized synchrotron radiation from accreting black holes, particularly in the context of the EHT sources M87 * and Sgr A * (e.g., Dexter 2016;Mościbrodzka & Gammie 2018;White 2022; and others; see also Gold et al 2020). However, no pitch-angle anisotropy was considered in these studies.…”

Section: Introductionmentioning

confidence: 99%

Polarized Anisotropic Synchrotron Emission and Absorption and Its Application to Black Hole Imaging

Galishnikova,

Philippov,

Quataert

2023

ApJ

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Low-collisionality plasma in a magnetic field generically develops anisotropy in its distribution function with respect to the magnetic field direction. Motivated by the application to radiation from accretion flows and jets, we explore the effect of temperature anisotropy on synchrotron emission. We derive analytically and provide numerical fits for the polarized synchrotron emission and absorption coefficients for a relativistic bi-Maxwellian plasma (we do not consider Faraday conversion/rotation). Temperature anisotropy can significantly change how the synchrotron emission and absorption coefficients depend on observing angle with respect to the magnetic field. The emitted linear polarization fraction does not depend strongly on anisotropy, while the emitted circular polarization does. We apply our results to black hole imaging of Sgr A* and M87* by ray tracing a GRMHD simulation and assuming that the plasma temperature anisotropy is set by the thresholds of kinetic-scale anisotropy-driven instabilities. We find that the azimuthal asymmetry of the 230 GHz images can change by up to a factor of 3, accentuating (T ⊥ > T ∥) or counteracting (T ⊥ < T ∥) the image asymmetry produced by Doppler beaming. This can change the physical inferences from observations relative to models with an isotropic distribution function, e.g., by allowing for larger inclination between the line of sight and spin direction in Sgr A*. The observed image diameter and the size of the black hole shadow can also vary significantly due to plasma temperature anisotropy. We describe how the anisotropy of the plasma can affect future multifrequency and photon ring observations. We also calculate kinetic anisotropy-driven instabilities (mirror, whistler, and firehose) for relativistically hot plasmas.

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Millimeter observational signatures of flares in magnetically arrested black hole accretion models

Jia,

Ripperda,

Quataert

et al. 2023

Monthly Notices of the Royal Astronomical Society

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In general relativistic magnetohydrodynamic (GRMHD) simulations, accreted magnetic flux on the black hole horizon episodically decays, during which magnetic reconnection heats up the plasma near the horizon, potentially powering high-energy flares like those observed in M87* and Sgr A*. We study the mm observational counterparts of such flaring episodes in very high resolution GRMHD simulations. The change in 230 GHz flux during the expected high energy flares depends primarily on the efficiency of accelerating γ ≳ 100 (Te ≳ 1011 K) electrons. For models in which the electrons are heated to Te ∼ 1011 K during flares, the hot plasma produced by reconnection significantly enhances 230 GHz emission and increases the size of the 230 GHz image. By contrast, for models in which the electrons are heated to higher temperatures (which we argue are better motivated), the reconnection-heated plasma is too hot to produce significant 230 GHz synchrotron emission, and the 230 GHz flux decreases during high energy flares. We do not find a significant change in the mm polarization during flares as long as the emission is Faraday thin. We also present expectations for the ring-shaped image as observed by the Event Horizon Telescope during flares, as well as multiwavelength synchrotron spectra. Our results highlight several limitations of standard post-processing prescriptions for the electron temperature in GRMHD simulations. We also discuss the implications of our results for current and future observations of flares in Sgr A*, M87*, and related systems. Appendices contain detailed convergence studies with respect to resolution and plasma magnetization.

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Blacklight: A General-relativistic Ray-tracing and Analysis Tool

Cited by 8 publications

References 51 publications

GYOTO 2.0: a polarized relativistic ray-tracing code

GYOTO 2.0: a polarized relativistic ray-tracing code

Polarized Anisotropic Synchrotron Emission and Absorption and Its Application to Black Hole Imaging

Millimeter observational signatures of flares in magnetically arrested black hole accretion models

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