The goal of this paper is to derive signatures of synchrotron radiation from state-of-the-art simulation models of collimating relativistic magnetohydrodynamic (MHD) jets featuring a large-scale helical magnetic field. We perform axisymmetric special relativistic MHD simulations of the jet acceleration region using the PLUTO code. The computational domain extends from the slow magnetosonic launching surface of the disk up to 6000^2 Schwarzschild radii allowing to reach highly relativistic Lorentz factors. The Poynting dominated disk wind develops into a jet with Lorentz factors of 8 and is collimated to 1 degree. In addition to the disk jet, we evolve a thermally driven spine jet, emanating from a hypothetical black hole corona. Solving the linearly polarized synchrotron radiation transport within the jet, we derive VLBI radio and (sub-) mm diagnostics such as core shift, polarization structure, intensity maps, spectra and Faraday rotation measure (RM), directly from the Stokes parameters. We also investigate depolarization and the detectability of a lambda^2-law RM depending on beam resolution and observing frequency. We find non-monotonic intrinsic RM profiles which could be detected at a resolution of 100 Schwarzschild radii. In our collimating jet geometry, the strict bi-modality in polarization direction (as predicted by Pariev et al.) can be circumvented. Due to relativistic aberration, asymmetries in the polarization vectors across the jet can hint to the spin direction of the central engine.
It is well-known that magnetohydrodynamic (MHD) turbulence is ubiquitous in astrophysical environments. The correct understanding of the fundamental properties of MHD turbulence is a prerequisite for revealing many key astrophysical processes. The development of observation-based measurement techniques has significantly promoted MHD turbulence theory and its implications in astrophysics. After describing the modern understanding of MHD turbulence based on theoretical analysis and direct numerical simulations, we review recent developments related to synchrotron fluctuation techniques. Specific…
We study the observable properties of compressible MHD turbulence covering different turbulence regimes, based on synthetic synchrotron observations arising from 3D MHD numerical simulations. Using the synchrotron emissivity and intensity, we first explore how the cosmic ray spectral indices affect the measurements of turbulence properties by employing normalized correlation functions. We then study how the anisotropy of synchrotron total and polarization intensities arising from three fundamental MHD modes vary with the viewing angle, i.e., the angle between the mean magnetic field and the li…
Blazars are a sub-category of radio-loud active galactic nuclei with relativistic jets pointing towards the observer. They exhibit non-thermal variable emission, which practically extends over the whole electromagnetic spectrum. Despite the plethora of multi-wavelength observations, the origin of the emission in blazar jets remains an open question. In this work, we construct a two-zone leptonic model: particles accelerate in a small region and lose energy through synchrotron radiation and inverse Compton Scattering. Consequently, the relativistic electrons escape to a larger area where the am…
We examine the evolution and emission of the supernova remnant (SNR) CTB109 using three-dimensional magnetohydrodynamics simulations. The SNR evolves in a medium divided by a plane interface into two media with different densities and pressure equilibrium. Our results reveal that a remnant with the characteristics of CTB109 is formed provided the supernova (SN) explosion takes place in the less dense medium and also if the interstellar magnetic field (ISMF) is almost uniform. Finally, we conclude that the quasiparallel mechanism can explain the brightness synchrotron emission and the position …
Blazars, a class of active galaxies whose jets are relativistic and collimated flows of plasma directed along the line of sight and are prone to a slew of magneto-hydrodynamic (MHD) instabilities. We aim to study the interplay of radiation and particle acceleration processes in regulating the multi-band emission and variability signatures from blazars. In particular, the goal is to decipher the impact of shocks arising due to MHD instabilities in driving the longterm variable emission signatures from blazars. In this regard, we have performed RMHD simulations of a representative section of bla…
We have simulated the evolution of non-thermal cosmic ray electrons (CREs) in 3D relativistic magneto hydrodynamic (MHD) jets evolved up to a height of 9 kpc. The CREs have been evolved in space and in energy concurrently with the relativistic jet fluid, duly accounting for radiative losses and acceleration at shocks. We show that jets stable to MHD instabilities show expected trends of regular flow of CREs in the jet spine and acceleration at a hotspot followed by a settling backflow. However, unstable jets create complex shock structures at the jet-head (kink instability), the jet spine-coco…
X-ray observations of several kiloparsec-scale extragalactic jets favour a synchrotron origin. The short cooling times of the emitting electrons requires distributed acceleration of electrons up to sub-PeV energies. In a previous paper, we found that this can be self-consistently explained by a shear acceleration model, where particles are accelerated to produce power-law spectra with a spectral index being determined mainly by the velocity profile and turbulence spectrum. In this paper, we perform 3D relativistic magneto-hydrodynamic simulations to investigate the formation of a spine-sheath …
Sagittarius A* exhibits regular variability in its multiwavelength emission, including daily X-ray flares and roughly continuous near-infrared (NIR) flickering. The origin of this variability is still ambiguous since both inverse Compton and synchrotron emission are possible radiative mechanisms. The underlying particle distributions are also not well constrained, particularly the non-thermal contribution. In this work, we employ the GPU-accelerated general relativistic magnetohydrodynamics (GRMHD) code H-AMR perform a study of flare flux distributions, including the effect of particle acceler…
Broad-band Spectral Modeling of Large-Scale X-ray Jets in High-Redshift Quasars: An MHD-Informed Approach
Astronomical Observatory of the Jagiellonian University（雅盖隆大学天文台）；Jagiellonian University（雅盖隆大学）；Naval Research Laboratory（海军研究实验室）；INAF—Istituto di Radioastronomia（意大利国家天体物理研究所射电天文台）；Center for Astrophysics, Harvard & Smithsonian（哈佛与史密森尼天体物理中心）
