Accessing a New Population of Supermassive Black Holes with Extensions to the Event Horizon Telescope
: Zhang, Xinyue Alice; Ricarte, Angelo; Pesce, Dominic W.; Johnson, Michael D.; Nagar, Neil; Narayan, Ramesh; Ramakrishnan, Venkatessh; Doeleman, Sheperd; Palumbo, Daniel C. M.
Publisher: IOP Publishing Ltd
: BRISTOL
: 2025
: Astrophysical Journal
: ASTROPHYSICAL JOURNAL
: ASTROPHYS J
: 41
: 985
: 1
: 19
: 0004-637X
: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/adbd45
: https://iopscience.iop.org/article/10.3847/1538-4357/adbd45
: https://research.utu.fi/converis/portal/detail/Publication/492257093
The Event Horizon Telescope (EHT) has produced resolved images of the supermassive black holes (SMBHs) Sgr A* and M87*, which present the largest shadows on the sky. In the next decade, technological improvements and extensions to the array will enable access to a greater number of sources, unlocking studies of a larger population of SMBHs through direct imaging. In this paper, we identify 12 of the most promising sources beyond Sgr A* and M87* based on their angular size and millimeter flux density. For each of these sources, we make theoretical predictions for their observable properties by ray tracing general relativistic magnetohydrodynamic models appropriately scaled to each target's mass, distance, and flux density. We predict that these sources would have somewhat higher Eddington ratios than M87*, which may result in larger optical and Faraday depths than previous EHT targets. Despite this, we find that visibility amplitude size constraints can plausibly recover masses within a factor of 2, although the unknown jet contribution remains a significant uncertainty. We find that the linearly polarized structure evolves substantially with the Eddington ratio, with greater evolution at larger inclinations, complicating potential spin inferences for inclined sources. We discuss the importance of 345 GHz observations, milli-Jansky baseline sensitivity, and independent inclination constraints for future observations with upgrades to the EHT through ground updates with the next-generation EHT program and extensions to space through the black hole Explorer.
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This project/publication is funded in part by the Gordon and Betty Moore Foundation (Grant #8273.01). It is also made possible through the support of a grant from the John Templeton Foundation (Grant #62286). The opinions expressed in this publication are those of the author(s) and do not necessarily reflect the views of these foundations. This work was also supported by the National Science Foundation (AST-2307887, AST-1935980, and AST-2034306), the Brinson Foundation, and the Gordon and Betty Moore Foundation (GBMF10423). We acknowledge funding from ANID Chile via Nucleo Milenio TITANs (NCN2023_002), Fondecyt Regular (1221421), and Basal (FB210003).
This research has made use of data obtained from the Chandra Source Catalog, provided by the Chandra X-ray Center (CXC) as part of the Chandra Data Archive. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology.
