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Abstract We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A* taken with the Event Horizon Telescope in 2017 April at a wavelength of 1.3 mm. Imaging of Sgr A* has been conducted through surveys over a wide range of imaging assumptions using the classical CLEAN algorithm, regularized maximum likelihood methods, and a Bayesian posterior sampling method. Different prescriptions have been used to account for scattering effects by the interstellar medium toward the Galactic center. Mitigation of the rapid intraday variability that characterizes Sgr A* has been carried out through the addition of a “variability noise budget” in the observed visibilities, facilitating the reconstruction of static full-track images. Our static reconstructions of Sgr A* can be clustered into four representative morphologies that correspond to ring images with three different azimuthal brightness distributions and a small cluster that contains diverse nonring morphologies. Based on our extensive analysis of the effects of sparse ( u , v )-coverage, source variability, and interstellar scattering, as well as studies of simulated visibility data, we conclude that the Event Horizon Telescope Sgr A* data show compelling evidence for an image that is dominated by a bright ring of emission with a ring diameter of ∼50 μ as, consistent with the expected “shadow” of a 4 × 10 6 M ⊙ black hole in the Galactic center located at a distance of 8 kpc.
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This content will become publicly available on January 1, 2026
ScatteringOptics.jl: An Interstellar Scattering Framework in the Julia Programming Language
ScatteringOptics.jl is an astronomy software package developed in the Julia programming language (Bezanson et al., 2017). It implements physical models for the anisotropic scattering of radio waves, which arise from turbulence in the ionized interstellar medium. This toolkit excels in simulating and modeling the temporal, spatial, and spectral effects of interstellar scintillation in the strong scattering regime, taking advantage of Julia’s speed and composability. The package provides essential functionalities for modeling, analyzing, and interpreting the images of the Galactic Center’s supermassive black hole, Sagittarius A*, especially with the Event Horizon Telescope (EHT), as well as the images of extremely high brightness temperature emissions in active galactic nuclei using space very long baseline interferometry.
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- Award ID(s):
- 2107681
- PAR ID:
- 10618363
- Editor(s):
- Foreman-Mackey, Dan
- Publisher / Repository:
- Journal of Open Source Software
- Date Published:
- Journal Name:
- Journal of Open Source Software
- Volume:
- 10
- Issue:
- 105
- ISSN:
- 2475-9066
- Page Range / eLocation ID:
- 6354
- Subject(s) / Keyword(s):
- astronomy VLBI black holes radio astronomy Julia
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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