RadioAstron Space VLBI Imaging of the Jet in M87. I. Detection of High Brightness Temperature at 22 GHz

Kim, Jae-Young; Savolainen, Tuomas; Voitsik, Petr; Kravchenko, Evgeniya V.; Lisakov, M. M.; Kovalev, Y. Y.; Müller, Hendrik; Lobanov, A. P.; Sokolovsky, K. V.; Bruni, G.; Edwards, Philip; Reynolds, C.; Bach, U.; Gurvits, L. I.; Krichbaum, T. P.; Hada, Kazuhiro; Giroletti, M.; Orienti, M.; Anderson, J. M.; Lee, Sang-Sung; Sohn, Bong Won; Zensus, J. A.

doi:10.3847/1538-4357/accf17

Cited by 5 publications

(2 citation statements)

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“…Additionally, Radio Astron's 22 GHz observations (Kim et al 2023) show a 0.36 mas core extending north-south, with a bright south side. This size is similar to that of the core region including both wings at 230 GHz; the south wing is brighter and larger at 230 GHz, consistent with the 22 GHz core's brightness distribution.…”

Section: The Structure Of the Core Region In M87mentioning

confidence: 99%

The Jet and Resolved Features of the Central Supermassive Black Hole of M87 Observed with EHT in 2017—Comparison with the GMVA 86 GHz Results

Miyoshi,

Kato,

Makino

et al. 2024

ApJL

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M87 is the best target for studying black hole accretion and jet formation. Reanalysis of the Event Horizon Telescope (EHT) public data at 230 GHz shows a core–knots structure at the center and jet features. We here compare this with the new results of GMVA at 86 GHz showing a spatially resolved central core. There are similarities and differences between the two. At 86 GHz, “two bright regions” are seen on the ring in the core. The “core–knot–west knot” triple structure in the 230 GHz image shows apparent appearance of two peaks similar to the “two bright regions” when convolved with the GMVA beam. This similarity suggests that both frequencies reveal the same objects in the core area. Protrusions are observed on both the south and north sides of the core at both frequencies, becoming prominent and winglike at 230 GHz. The 86 GHz image shows a triple ridge jet structure, while the 230 GHz image shows only a bright central ridge with two roots. Both frequencies show a shade between the core and the central ridge. To detect the faint features from the EHT2017 data, we found that the use of all baseline data is essential. Using all baseline data, including the ultrashort data, revealed the jet and faint structures. Without the ultrashort baselines, these structures were not detectable. The lack of detection of any faint structures other than the ring in the M87 data by the EHTC is presumably due to the exclusion of ultrashort baselines from their analysis.

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Section: The Structure Of the Core Region In M87mentioning

confidence: 99%

The Jet and Resolved Features of the Central Supermassive Black Hole of M87 Observed with EHT in 2017—Comparison with the GMVA 86 GHz Results

Miyoshi,

Kato,

Makino

et al. 2024

ApJL

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“…However, recent years have seen the ongoing development of novel imaging algorithms for the global VLBI data regime, primarily inspired by the needs of the Event Horizon Telescope (EHT), in three main families: super-resolving CLEAN-based algorithms (Müller & Lobanov 2023b), Bayesian methods (Arras et al 2021;Broderick et al 2020b;Tiede 2022), and regularized maximum likelihood (RML) methods (Honma et al 2014;Chael et al 2016Chael et al , 2018Akiyama et al 2017b,a;Müller & Lobanov 2022). These methods have been proven to be successful when applied to synthetic data (Event Horizon Telescope Collaboration 2019, 2022a and in a wide range of frontline observations with the EHT (Event Horizon Telescope Collaboration 2019, 2022a; Kim et al 2020;Janssen et al 2021;Issaoun et al 2022;Jorstad et al 2023), the Global Millimetre VLBI Array (GMVA) observations (Zhao et al 2022), and space-VLBI (Fuentes et al 2023;Müller & Lobanov 2023a;Kim et al 2023). One issue is that the image structure is only weakly constrained by the data and multiple solutions may fit the observed data; this is handled within these frameworks either via manual interaction in CLEAN (CLEAN windows, hybrid imaging, and self-calibration), a global posterior evaluation for Bayesian methods, or the combination of various data terms and regularization terms for RML methods.…”

Section: Introductionmentioning

confidence: 99%

Using multiobjective optimization to reconstruct interferometric data

Mus,

Müller,

Martí-Vidal

et al. 2024

A&A

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In very long baseline interferometry (VLBI), signals recorded at multiple antennas are combined to form a sparsely sampled virtual aperture with an effective diameter set by the largest separation between the antennas. Due to the sparsity of the sampled aperture, VLBI imaging constitutes an ill-posed inverse problem. Various algorithms have been employed to deal with the VLBI imaging, including the recently proposed multiobjective evolutionary algorithm by decomposition (MOEA/D) described in the first paper of this series. Among the approaches to the reconstruction of the image features in total intensity from sparsely sampled visibilities, extensions to the polarimetric and the temporal domain are of great interest for the VLBI community in general and the Event Horizon Telescope Collabroration (EHTC) in particular. Based on the success of MOEA/D in presenting an alternative claim of the image structure in a unique, fast, and largely unsupervised way, we study the extension of MOEA/D to polarimetric and time dynamic reconstructions in this paper. To this end, we utilized the multiobjective, evolutionary framework introduced for MOEA/D, but added the various penalty terms specific to total intensity imaging time-variable and polarimetric variants, respectively. We computed the Pareto front (the sample of all non-dominated solutions) and identified clusters of close proximities. We tested MOEA/D with synthetic data sets that are representative for the main science targets and instrumental configuration of the EHTC and its possible successors. We successfully recovered the polarimetric and time-dynamic signature of the ground truth movie (even with relative sparsity) and a set of realistic data corruptions. MOEA/D has been successfully extended to polarimetric and time-dynamic reconstructions and, specifically, in a setting that would be expected for the EHTC. It offers a unique alternative and independent claim to the already existing methods, along with a number of additional benefits, namely: it is the first method that effectively explores the problem globally and compared to regularized maximum likelihood (RML) methods. Thus, it waives the need for parameter surveys. Hence, MOEA/D is a novel, useful tool to characterize the polarimetric and dynamic signatures in a VLBI data set robustly with a minimal set of user-based choices. In a consecutive work, we will address the last remaining limitation for MOEA/D (the number of pixels and numerical performance), so that MOEA/D can firmly solidify its place within the VLBI data reduction pipeline.

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Observational evidence to support a dense ambient medium shaping the jet in 3C 84

Park,

Kino,

Nagai

et al. 2024

A&A

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Highly collimated relativistic jets are a defining feature of certain active galactic nuclei (AGN), yet their formation mechanism remains elusive. Previous observations and theoretical models have proposed that the ambient medium surrounding the jets could exert pressure, playing a crucial role in shaping the jets. However, a direct observational confirmation of such a medium has been lacking. In this study, we present very long baseline interferometric (VLBI) observations of 3C 84 (NGC 1275), located at the center of the Perseus Cluster. Through monitoring observations with the Very Long Baseline Array (VLBA) at 43 GHz, a jet knot was detected to have been ejected from the sub-parsec scale core in the late 2010s. Intriguingly, this knot propagated in a direction significantly offset from the parsec-scale jet direction. To delve deeper into the matter, we employed follow-up VLBA 43 GHz observations, tracing the knot's trajectory until the end of 2022. We discovered that the knot abruptly changed its trajectory in the early 2020s, realigning itself with the parsec-scale jet direction. Additionally, we present results from an observation of 3C 84 with the Global VLBI Alliance (GVA) at 22 GHz, conducted near the monitoring period. By jointly analyzing the GVA 22 GHz image with a VLBA 43 GHz image observed about one week apart, we generated a spectral index map, revealing an inverted spectrum region near the edge of the jet where the knot experienced deflection. These findings suggest the presence of a dense, cold ambient medium characterized by an electron density exceeding $ $, which guides the jet's propagation on parsec scales and significantly contributes to the overall shaping of the jet.

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RadioAstron Space VLBI Imaging of the Jet in M87. I. Detection of High Brightness Temperature at 22 GHz

Cited by 5 publications

References 81 publications

The Jet and Resolved Features of the Central Supermassive Black Hole of M87 Observed with EHT in 2017—Comparison with the GMVA 86 GHz Results

The Jet and Resolved Features of the Central Supermassive Black Hole of M87 Observed with EHT in 2017—Comparison with the GMVA 86 GHz Results

Using multiobjective optimization to reconstruct interferometric data

Observational evidence to support a dense ambient medium shaping the jet in 3C 84

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