scholarly journals Polarization imaging of M 87 jets by general relativistic radiative transfer calculation based on GRMHD simulations

2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Yuh Tsunetoe ◽  
Shin Mineshige ◽  
Ken Ohsuga ◽  
Tomohisa Kawashima ◽  
Kazunori Akiyama
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Radiative Transfer ◽  
Circular Polarization ◽  
Polarized Light ◽  
Polarization Degree ◽  
Emission Region ◽  
Magnetic Field Direction ◽  
Accretion Flow ◽  
General Relativistic

Abstract The spectacular images of the M 87 black hole taken by the Event Horizon Telescope (EHT) have opened a new era of black hole research. One of the next issues is to take polarization images around the central black hole (BH). Since radio emission is produced by synchrotron process, polarization properties should vividly reflect the magnetic field structures at the jet base and thus provide good information regarding the magnetic mechanism of jet formation. With this kept in mind we perform general relativistic (GR) radiative transfer calculations of polarized light based on the GR magnetohydrodynamic (MHD) simulation data of accretion flow and outflow in M 87, to obtain their linear and circular polarization images in the BH horizon-scale. We found that the linear polarization components originating from the jet base and inner accretion flow should experience Faraday rotation and depolarization when passing through magnetized plasmas around the BH, thus sensitively depending on the BH spin. Through the comparison with total intensity image at $1.3\:$mm by EHT and the polarization degree and the rotation measure (RM) measured at $1.3\:$mm with the Submillimeter Array, the model with the spin parameter of $a=0.9\, M_{\,\mathrm{BH}}$ (with $M_{\,\mathrm{BH}}$ being the BH mass) is favored over other models with $a = 0.5\, M_{\,\mathrm{BH}}$ or $0.99\, M_{\,\mathrm{BH}}$, though we need further systematic studies for confirmation. We also find in low-temperature models a clear ring-like image in the circular polarization map, which arises because of Faraday conversion of the linearly polarized synchrotron emission and is thus indicative of magnetic field direction. This occurs only when the emission region is threaded with well-ordered magnetic fields and hence no clear images are expected in high-temperature disk models, in which disk emission is appreciable. We will be able to elucidate the field configuration through the comparison between the simulated polarization images and future polarimetry with EHT and other VLBI observations.

scholarly journals How to tell an accreting boson star from a black hole

2020 ◽  
Vol 497 (1) ◽  
pp. 521-535 ◽  
Author(s):  
Hector Olivares ◽  
Ziri Younsi ◽  
Christian M Fromm ◽  
Mariafelicia De Laurentis ◽  
Oliver Porth ◽  
...  
Keyword(s):  
Black Hole ◽  
Radiative Transfer ◽  
Event Horizon ◽  
Polar Regions ◽  
Radio Observations ◽  
Accretion Flow ◽  
Supermassive Black Hole ◽  
General Relativistic ◽  
Sgr A ◽  
Magnetohydrodynamic Simulations

ABSTRACT The capability of the Event Horizon Telescope (EHT) to image the nearest supermassive black hole candidates at horizon-scale resolutions offers a novel means to study gravity in its strongest regimes and to test different models for these objects. Here, we study the observational appearance at 230 GHz of a surfaceless black hole mimicker, namely a non-rotating boson star, in a scenario consistent with the properties of the accretion flow on to Sgr A*. To this end, we perform general relativistic magnetohydrodynamic simulations followed by general relativistic radiative transfer calculations in the boson star space–time. Synthetic reconstructed images considering realistic astronomical observing conditions show that, despite qualitative similarities, the differences in the appearance of a black hole – either rotating or not – and a boson star of the type considered here are large enough to be detectable. These differences arise from dynamical effects directly related to the absence of an event horizon, in particular, the accumulation of matter in the form of a small torus or a spheroidal cloud in the interior of the boson star, and the absence of an evacuated high-magnetization funnel in the polar regions. The mechanism behind these effects is general enough to apply to other horizonless and surfaceless black hole mimickers, strengthening confidence in the ability of the EHT to identify such objects via radio observations.

scholarly journals Influence of the geometric configuration of accretion flow on the black hole spin dependence of relativistic acoustic geometry

2018 ◽  
Vol 27 (03) ◽  
pp. 1850023 ◽  
Author(s):  
Pratik Tarafdar ◽  
Tapas K. Das
Keyword(s):  
Black Hole ◽  
Kerr Black Hole ◽  
Geometric Configuration ◽  
Surface Gravity ◽  
Linear Perturbation ◽  
Flow Profile ◽  
White Hole ◽  
Accretion Flow ◽  
Black Hole Spin ◽  
General Relativistic

Linear perturbation of general relativistic accretion of low angular momentum hydrodynamic fluid onto a Kerr black hole leads to the formation of curved acoustic geometry embedded within the background flow. Characteristic features of such sonic geometry depend on the black hole spin. Such dependence can be probed by studying the correlation of the acoustic surface gravity [Formula: see text] with the Kerr parameter [Formula: see text]. The [Formula: see text]–[Formula: see text] relationship further gets influenced by the geometric configuration of the accretion flow structure. In this work, such influence has been studied for multitransonic shocked accretion where linear perturbation of general relativistic flow profile leads to the formation of two analogue black hole-type horizons formed at the sonic points and one analogue white hole-type horizon which is formed at the shock location producing divergent acoustic surface gravity. Dependence of the [Formula: see text]–[Formula: see text] relationship on the geometric configuration has also been studied for monotransonic accretion, over the entire span of the Kerr parameter including retrograde flow. For accreting astrophysical black holes, the present work thus investigates how the salient features of the embedded relativistic sonic geometry may be determined not only by the background spacetime, but also by the flow configuration of the embedding matter.

scholarly journals Modelling the polarised emission from black holes on event horizon-scales

2020 ◽  
Vol 14 (S342) ◽  
pp. 9-12 ◽  
Author(s):  
Ziri Younsi ◽  
Oliver Porth ◽  
Yosuke Mizuno ◽  
Christian M. Fromm ◽  
Hector Olivares
Keyword(s):  
Black Holes ◽  
Radiative Transfer ◽  
Event Horizon ◽  
Theoretical Description ◽  
Accretion Flow ◽  
Fundamental Properties ◽  
Sagittarius A ◽  
General Relativistic ◽  
Realistic Images ◽  
Insight Into

AbstractUpcoming VLBI observations will resolve nearby supermassive black holes, most notably Sagittarius A* and M87, on event horizon-scales. Recent observations of Sagittarius A* with the Event Horizon Telescope have revealed horizon-scale structure. Accordingly, the detection and measurement of the back hole “shadow” is expected to enable the existence of astrophysical black holes to be verified directly. Although the theoretical description of the shadow is straightforward, its observational appearance is largely determined by the properties of the surrounding accretion flow, which is highly turbulent. We introduce a new polarised general-relativistic radiative transfer code, BHOSS, which accurately solves the equations of polarised radiative transfer in arbitrary strong-gravity environments, providing physically-realistic images of astrophysical black holes on event horizon-scales, as well as also providing insight into the fundamental properties and nature of the surrounding accretion flow environment.

scholarly journals ENERGY ASSOCIATED WITH SCHWARZSCHILD BLACK HOLE IN A MAGNETIC UNIVERSE

2000 ◽  
Vol 15 (19) ◽  
pp. 2979-2986 ◽  
Author(s):  
S. S. XULU
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Uniform Magnetic Field ◽  
Relativistic Effect ◽  
Rest Mass ◽  
Mass Energy ◽  
Schwarzschild Black Hole ◽  
General Relativistic ◽  
The Magnetic Field ◽  
General Relativistic Effect

In this paper we obtain the energy distribution associated with the Ernst space–time (geometry describing Schwarzschild black hole in Melvin's magnetic universe) in Einstein's prescription. The first term is the rest-mass energy of the Schwarzschild black hole, the second term is the classical value for the energy of the uniform magnetic field and the remaining terms in the expression are due to the general relativistic effect. The presence of the magnetic field is found to increase the energy of the system.

scholarly journals Positron Effects on Polarized Images and Spectra from Jet and Accretion Flow Models of M87* and Sgr A*

2021 ◽  
Vol 923 (2) ◽  
pp. 272
Author(s):  
Razieh Emami ◽  
Richard Anantua ◽  
Andrew A. Chael ◽  
Abraham Loeb
Keyword(s):  
Power Law ◽  
Pressure Ratio ◽  
Spectral Energy ◽  
Emission Region ◽  
Flow Models ◽  
Accretion Flow ◽  
Positron Fraction ◽  
General Relativistic ◽  
Sgr A ◽  
Polarization Fraction

Abstract We study the effects of including a nonzero positron-to-electron fraction in emitting plasma on the polarized spectral energy distributions and submillimeter images of jet and accretion flow models for near-horizon emission from M87* and Sgr A*. For M87*, we consider a semi-analytic fit to the force-free plasma regions of a general relativistic magnetohydrodynamic jet simulation, which we populate with power-law leptons with a constant electron-to-magnetic pressure ratio. For Sgr A*, we consider a standard self-similar radiatively inefficient accretion flow where the emission is predominantly from thermal leptons with a small fraction in a power-law tail. In both models, we fix the positron-to-electron ratio throughout the emission region. We generate polarized images and spectra from our models using the general relativistic ray tracing and radiative transfer from GRTRANS. We find that a substantial positron fraction reduces the circular polarization fraction at IR and higher frequencies. However, in submillimeter images, higher positron fractions increase polarization fractions due to strong effects of Faraday conversion. We find an M87* jet model that best matches the available broadband total intensity, and 230 GHz polarization data is a sub-equipartition, with positron fraction of ≃10%. We show that jet models with significant positron fractions do not satisfy the polarimetric constraints at 230 GHz from the Event Horizon Telescope (EHT). Sgr A* models show similar trends in their polarization fractions with increasing pair fraction. Both models suggest that resolved, polarized EHT images are useful to constrain the presence of pairs at 230 GHz emitting regions of M87* and Sgr A*.

scholarly journals Referencing the Polarization Orientation to the Emission-Region Magnetic Field

2017 ◽  
Vol 13 (S337) ◽  
pp. 404-405
Author(s):  
Joanna M. Rankin
Keyword(s):  
Magnetic Field ◽  
Proper Motion ◽  
Rotation Axis ◽  
Field Direction ◽  
Emission Region ◽  
Magnetic Field Direction ◽  
Axis Orientation ◽  
Physical Foundation ◽  
Polarization Orientation ◽  
The Magnetic Field

AbstractUsing the proper-motion as a proxy for a pulsar’s rotation-axis orientation, the emission polarization can be related to the magnetic field direction in the emission region, providing a much more physical foundation for understanding orthogonal mode radiation.

scholarly journals Extraction of Black Hole Rotational Energy by a Magnetic Field

2003 ◽  
Vol 214 ◽  
pp. 87-90
Author(s):  
Shinji Koide
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Large Scale ◽  
Kerr Black Hole ◽  
Negative Energy ◽  
Rotational Energy ◽  
Alfven Wave ◽  
Numerical Result ◽  
General Relativistic ◽  
Magnetohydrodynamic Simulations

We have developed a numerical method for general relativistic magnetohydrodynamic simulations in Kerr space-time. The method is applied to the basic astrophysical problem of the Kerr black hole activity in the large-scale strong magnetic field. The numerical result shows that the magnetic field extracts the rotational energy of the black hole with negative energy-at-infinity and the torsional Alfven wave is induced from the ergosphere.

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