Accretion Flow Morphology in Numerical Simulations of Black Holes from the ngEHT Model Library: The Impact of Radiation Physics

Abstract

In the past few years, the Event Horizon Telescope (EHT) has provided the first-ever event horizon-scale images of the supermassive black holes (BHs) M87* and Sagittarius A* (Sgr A*). The next-generation EHT project is an extension of the EHT array that promises larger angular resolution and higher sensitivity to the dim, extended flux around the central ring-like structure, possibly connecting the accretion flow and the jet. The ngEHT Analysis Challenges aim to understand the science extractability from synthetic images and movies to inform the ngEHT array design and analysis algorithm development. In this work, we compare the accretion flow structure and dynamics in numerical fluid simulations that specifically target M87* and Sgr A*, and were used to construct the source models in the challenge set. We consider (1) a steady-state axisymmetric radiatively inefficient accretion flow model with a time-dependent shearing hotspot, (2) two time-dependent single fluid general relativistic magnetohydrodynamic (GRMHD) simulations from the H-AMR code, (3) a two-temperature GRMHD simulation from the BHAC code, and (4) a two-temperature radiative GRMHD simulation from the KORAL code. We find that the different models exhibit remarkably similar temporal and spatial properties, except for the electron temperature, since radiative losses substantially cool down electrons near the BH and the jet sheath, signaling the importance of radiative cooling even for slowly accreting BHs such as M87*. We restrict ourselves to standard torus accretion flows, and leave larger explorations of alternate accretion models to future work.

Magnetic Flux Plays an Important Role during a Black Hole X-Ray Binary Outburst in Radiative Two-temperature General Relativistic Magnetohydrodynamic Simulations

“…Edd ), radiative cooling of the electrons becomes efficient, leading to a drop in electron temperature but no other structural change (see also Chatterjee et al 2023). In the third stage…”

“…Our MAD model (XRB MAD), on the other hand, features a much larger torus with r in = 20 r g and = r r 41 g max whose outer edge lies at r out ∼ 800 r g . These tori are pretty standard choices in the GRMHD community (e.g., Porth et al 2019;Chatterjee et al 2023). We thread the SANE model with magnetic vector potential,…”

Dynamic and Polarimetric VLBI imaging with a multiscalar approach

“…The ground truth movies produced for the ngEHT Analysis challenge resemble the current theoretical state-of-the-art in simulations (Roelofs et al 2023;Chatterjee et al 2023). Here we present the reconstructions of a RIAF model of Sgr A* (Broderick et al 2016) with a shearing hotspot (Tiede et al 2020) with hotspot parameters inspired by GRAVITY Collaboration et al (2018a).…”

How to Turn Jets into Cylinders near Supermassive Black Holes in 3D General Relativistic Magnetohydrodynamic Simulations

“…Significant progress has been made in describing the jet formation and propagation analytically and numerically (e.g., De Villiers et al 2005;McKinney 2006;McKinney & Narayan 2007;Lyubarsky 2009;Tchekhovskoy et al 2011;Chatterjee et al 2019Chatterjee et al , 2023; for reviews, see Blandford et al 2019;Davis & Tchekhovskoy 2020). Bromberg et al (2011) developed an analytical model of the relativistic unmagnetized jet propagating in the ambient medium.…”