TY  - JOUR
A1  - Roelofs, Freek
A1  - Blackburn, Lindy
A1  - Lindahl, Greg
A1  - Doeleman, Sheperd S.
A1  - Johnson, Michael D.
A1  - Arras, Philipp
A1  - Chatterjee, Koushik
A1  - Emami, Razieh
A1  - Fromm, Christian
A1  - Fuentes, Antonio
A1  - Knollmüller, Jakob
A1  - Kosogorov, Nikita
A1  - Müller, Hendrik
A1  - Patel, Nimesh
A1  - Raymond, Alexander
A1  - Tiede, Paul
A1  - Traianou, Efthalia
A1  - Vega, Justin
T1  - The ngEHT analysis challenges
JF  - Galaxies
N2  - The next-generation Event Horizon Telescope (ngEHT) will be a significant enhancement of the Event Horizon Telescope (EHT) array, with ∼10 new antennas and instrumental upgrades of existing antennas. The increased uv-coverage, sensitivity, and frequency coverage allow a wide range of new science opportunities to be explored. The ngEHT Analysis Challenges have been launched to inform the development of the ngEHT array design, science objectives, and analysis pathways. For each challenge, synthetic EHT and ngEHT datasets are generated from theoretical source models and released to the challenge participants, who analyze the datasets using image reconstruction and other methods. The submitted analysis results are evaluated with quantitative metrics. In this work, we report on the first two ngEHT Analysis Challenges. These have focused on static and dynamical models of M87* and Sgr A* and shown that high-quality movies of the extended jet structure of M87* and near-horizon hourly timescale variability of Sgr A* can be reconstructed by the reference ngEHT array in realistic observing conditions using current analysis algorithms. We identify areas where there is still room for improvement of these algorithms and analysis strategies. Other science cases and arrays will be explored in future challenges.
KW  - very long baseline interferometry
KW  - black holes
KW  - active galactic nuclei
KW  - radio astronomy
KW  - imaging
KW  - instrument design
KW  - telescopes
KW  - algorithms
KW  - data analysis
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-304976
SN  - 2075-4434
VL  - 11
IS  - 1
ER  - 
TY  - JOUR
A1  - Chatterjee, Koushik
A1  - Chael, Andrew
A1  - Tiede, Paul
A1  - Mizuno, Yosuke
A1  - Emami, Razieh
A1  - Fromm, Christian
A1  - Ricarte, Angelo
A1  - Blackburn, Lindy
A1  - Roelofs, Freek
A1  - Johnson, Michael D.
A1  - Doeleman, Sheperd S.
A1  - Arras, Philipp
A1  - Fuentes, Antonio
A1  - Knollmüller, Jakob
A1  - Kosogorov, Nikita
A1  - Lindahl, Greg
A1  - Müller, Hendrik
A1  - Patel, Nimesh
A1  - Raymond, Alexander
A1  - Traianou, Efthalia
A1  - Vega, Justin
T1  - Accretion flow morphology in numerical simulations of black holes from the ngEHT model library: the impact of radiation physics
JF  - Galaxies
N2  - 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.
KW  - black holes
KW  - general relativity
KW  - accretion
KW  - relativistic jets
KW  - very-long-baseline interferometry
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-304084
SN  - 2075-4434
VL  - 11
IS  - 2
ER  -