Locating the missing large-scale emission in the jet of M87* with short EHT baselines

In very-long baseline interferometric arrays, nearly co-located stations probe the largest scales and typically cannot resolve the observed source. In the absence of a large-scale structure, closure phases constructed with these stations are zero and, since they are independent of station-based errors, they can be used to probe data issues. Here, we show how these trivial closure phases become nonzero with a brightness distribution on smaller scales than their short baseline would suggest. When applied to sources that are made up of a bright compact and large-scale diffuse component, the trivial closure phases directly measure the centroid relative to the compact source and higher-order image moments. We present a technique to measure these image moments with minimal model assumptions and validate it on synthetic Event Horizon Telescope (EHT) data. We then apply this technique to 2017 and 2018 EHT observations of M87* and find a weak preference for extended emission in the direction of the large-scale jet. We also apply it to 2021 EHT data and measure the source centroid about 1 mas northwest of the compact ring, which is consistent with the jet observed at lower frequencies.

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Publication Details

Journal
Springer Link (Chiba Institute of Technology)
Published
2026-04-30
DOI
https://doi.org/10.1051/0004-6361/202557013/pdf
Primary Topic
Astrophysics and Cosmic Phenomena
Type
article
Field-Weighted Citation Impact
0.00

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article

Locating the missing large-scale emission in the jet of M87* with short EHT baselines

Iniyan Natarajan, Boris Georgiev, Michael Janssen, Iniyan Natarajan et al.
Springer Link (Chiba Institute of Technology)
Astrophysics and Cosmic Phenomena
article

Locating the missing large-scale emission in the jet of M87* with short EHT baselines

Iniyan Natarajan, Boris Georgiev, Michael Janssen, Iniyan Natarajan, Sebastiano D. von Fellenberg, Paul Tiede
article en

Abstract

In very-long baseline interferometric arrays, nearly co-located stations probe the largest scales and typically cannot resolve the observed source. In the absence of a large-scale structure, closure phases constructed with these stations are zero and, since they are independent of station-based errors, they can be used to probe data issues. Here, we show how these trivial closure phases become nonzero with a brightness distribution on smaller scales than their short baseline would suggest. When applied to sources that are made up of a bright compact and large-scale diffuse component, the trivial closure phases directly measure the centroid relative to the compact source and higher-order image moments. We present a technique to measure these image moments with minimal model assumptions and validate it on synthetic Event Horizon Telescope (EHT) data. We then apply this technique to 2017 and 2018 EHT observations of M87* and find a weak preference for extended emission in the direction of the large-scale jet. We also apply it to 2021 EHT data and measure the source centroid about 1 mas northwest of the compact ring, which is consistent with the jet observed at lower frequencies.

Springer Link (Chiba Institute of Technology)
National Science Foundation, Smithsonian Institution, U.S. Department of Energy, National Aeronautics and Space Administration, University of Chicago, University of Arizona, CERN, Netherlands eScience Center, Ministerio de Ciencia, Innovación y Universidades, National Radio Astronomy Observatory, POSCO TJ Park Foundation, Government of Canada, European Commission, National Research Foundation, University of Pretoria, Fundação de Amparo à Pesquisa do Estado de São Paulo, National Natural Science Foundation of China, Academia Sinica, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Chinese Academy of Sciences, Korea Astronomy and Space Science Institute, National Research Foundation of Korea, A.G. Leventis Foundation, Max-Planck-Gesellschaft, Vetenskapsrådet, China Scholarship Council, European Southern Observatory, Centre National de la Recherche Scientifique, Shanghai Jiao Tong University, National Astronomical Observatory of Japan, Ministry of Science and ICT, South Korea, Center for Research and Development in Mathematics and Applications, Alliance de recherche numérique du Canada, Institut Périmètre de physique théorique, Toray Science Foundation, Office of Science, National Nuclear Security Administration, HORIZON EUROPE Framework Programme, Natural Sciences and Engineering Research Council of Canada, Science and Technology Facilities Council, Fundação para a Ciência e a Tecnologia, National Institutes of Natural Sciences, Agencia Estatal de Investigación, National Key Research and Development Program of China, Oak Ridge National Laboratory, Los Alamos National Laboratory
Openalex Percentile: Top 57%
Astrophysics and Cosmic Phenomena
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