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

Abstract

We study the effects of including a nonzero positron-to-electron fraction in emitting plasma on the polarized SEDs and sub-millimeter 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 infrared and higher frequencies. However, in sub-millimeter images higher positron fractions increase polarization fractions due to strong effects of Faraday conversion. We find a M87* jet model that best matches the available broadband total intensity and 230 GHz polarization data is a sub-equipartition, with positron fraction of $\simeq$ 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*.

32 pages, 12 figures, accepted to ApJ

References in corpus (38)

• The NumPy array: a structure for efficient numerical computation
• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
• Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre
• First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon
• First M87 Event Horizon Telescope Results. VII. Polarization of the Ring
• Jet Launching Structure Resolved Near the Supermassive Black Hole in M87
• Fast variability of TeV gamma-rays from the radio galaxy M 87
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• MOJAVE: XV. VLBA 15 GHz Total Intensity and Polarization Maps of 437 Parsec-Scale AGN Jets From 1996-2017
• Kinematics of the jet in M87 on scales of 100 -- 1000 Schwarzschild radii
• The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations
• Observing the Inner Shadow of a Black Hole: A Direct View of the Event Horizon
• A Global 86GHz VLBI Survey of Compact Radio Sources
• The Disc-Jet Symbiosis Emerges: Modeling the Emission of Sagittarius A* with Electron Thermodynamics
• Plasma diagnostic potential of 2p4f in N${}^{+}$ -- accurate wavelengths and oscillator strengths
• The Power of Imaging: Constraining the Plasma Properties of GRMHD Simulations using EHT Observations of Sgr A*
• Radio and Millimeter Monitoring of Sgr A*: Spectrum, Variability, and Constraints on the G2 Encounter
• 230 GHz VLBI observations of M87: event-horizon-scale structure at the enhanced very-high-energy $\gamma$-ray state in 2012
• The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA
• Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
• Polarimetric properties of Event Horizon Telescope targets from ALMA
• Discriminating Accretion States via Rotational Symmetry in Simulated Polarimetric Images of M87
• The Submillimeter Polarization of Sgr A*
• Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope
• Pilot KaVA monitoring on the M87 jet: confirming the inner jet structure and superluminal motions at sub-pc scales
• Decomposing the Internal Faraday Rotation of Black Hole Accretion Flows
• The Jet-Disk Boundary Layer in Black Hole Accretion
• Linear polarization in the nucleus of M87 at 7 mm and 1.3 cm
• Hubble Space Telescope observations of an extraordinary flare in the M87 jet
• On the Comparison of AGN with GRMHD Simulations: I. Sgr A*
• Pair Drizzle around Sub-Eddington Supermassive Black Holes
• The Variability of Polarized Radiation from Sgr A*
• An accretion-jet model for M87: interpreting the spectral energy distribution and Faraday rotation measure

Cited by in corpus (10)

• First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
• First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
• Black Hole Magnetic Fields and Their Imprint on Circular Polarization Images
• Unraveling Twisty Linear Polarization Morphologies in Black Hole Images
• Using Machine Learning to Link Black Hole Accretion Flows with Spatially Resolved Polarimetric Observables
• How Spatially Resolved Polarimetry Informs Black Hole Accretion Flow Models
• Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes
• Illuminating Black Hole Shadow with Dark Matter Annihilation
• PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion
• Investigating the Disk-Jet Structure in M87 through Flux Separation in the Linear and Circular Polarization Images