RadioAstron discovers a mini-cocoon around the restarted parsec-scale jet in 3C 84

Savolainen, Tuomas; Giovannini, G.; Kovalev, Y. Y.; Perucho, Manuel; Anderson, J. M.; Bruni, G.; Edwards, Philip; Fuentes, Antonio; Giroletti, M.; Gómez, José L.; Hada, Kazuhiro; Lee, S. S.; Lisakov, M. M.; Lobanov, A. P.; López-Miralles, José; Orienti, M.; Petrov, Leonid; Plavin, A. V.; Sohn, Bong-Won; Sokolovsky, K. V.; Voitsik, P. A.; Zensus, J. A.

doi:10.48550/arxiv.2111.04481

Cited by 6 publications

(12 citation statements)

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“…A halo or cocoon enveloping the extended emission in the pc-scale region (detected at lower frequencies, e.g. Taylor & Vermeulen 1996;Silver et al 1998;Savolainen et al 2021) has been put forth in the past as a possible explanation of the jet collimation in 3C 84 (e.g. Nagai et al 2017;Giovannini et al 2018).…”

Section: Jet Collimationmentioning

confidence: 99%

Jet kinematics in the transversely stratified jet of 3C 84

Paraschos

Krichbaum

Kim

et al. 2022

A&A

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3C 84 (NGC 1275) is one of the brightest radio sources in the millimetre radio bands, which led to a plethora of very-long-baseline interferometry (VLBI) observations at numerous frequencies over the years. They reveal a two-sided jet structure, with an expanding but not well-collimated parsec-scale jet, pointing southward. High-resolution millimetre-VLBI observations allow the study and imaging of the jet base on a sub-parsec scale. This could facilitate the investigation of the nature of the jet origin, also in view of the previously detected two-railed jet structure and east-west oriented core region seen with RadioAstron at 22 GHz. We produced VLBI images of this core and inner jet region, observed over the past twenty years at 15, 43, and 86 GHz. We determined the kinematics of the inner jet and ejected features at 43 and 86 GHz and compared their ejection times with radio and γ-ray variability. For the moving jet features, we find an average velocity of β avg app = 0.055 − 0.22c (µ avg = 0.04 − 0.18 mas/yr). From the time-averaged VLBI images at the three frequencies, we measured the transverse jet width along the bulk flow. On the ≤ 1.5 parsec scale, we find a clear trend of the jet width being frequency dependent, with the jet being narrower at higher frequencies. This stratification is discussed in the context of a spine-sheath scenario, and we compare it to other possible interpretations. From quasi-simultaneous observations at 43 and 86 GHz, we obtain spectral index maps, revealing a time-variable orientation of the spectral index gradient due to structural variability of the inner jet.

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Section: Jet Collimationmentioning

confidence: 99%

Jet kinematics in the transversely stratified jet of 3C 84

Paraschos

Krichbaum

Kim

et al. 2022

A&A

Self Cite

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“…An extremely wide jet opening angle at a short distance from the core with clear limb-brightening allows us to study the transverse jet velocity structure and the origin of the jets. It has also been suggested by recent VLBI observations that the jet is actively interacting with the interstellar medium due to a strong collision with a compact dense cloud [125], as well as a cocoon-like structure surrounding the jet [126].…”

Section: C 84mentioning

confidence: 90%

Polarization Observations of AGN Jets: Past and Future

Park

Algaba

2022

Galaxies

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The magnetic field is believed to play a critical role in the bulk acceleration and propagation of jets produced in active galactic nuclei (AGN). Polarization observations of AGN jets provide valuable information about their magnetic fields. As a result of radiative transfer, jet structure, and stratification, among other factors, it is not always straightforward to determine the magnetic field structures from observed polarization. We review these effects and their impact on polarization emission at a variety of wavelengths, including radio, optical, and ultraviolet wavelengths in this paper. It is also possible to study the magnetic field in the launching and acceleration regions of AGN jets by using very long baseline interferometry (VLBI), which occurs on a small physical scale. Due to the weak polarization of the jets in these regions, probing the magnetic field is generally difficult. However, recent VLBI observations have detected significant polarization and Faraday rotation in some nearby sources. We present the results of these observations as well as prospects for future observations. Additionally, we briefly discuss recently developed polarization calibration and imaging techniques for VLBI data, which enable more in-depth analysis of the magnetic field structure around supermassive black holes and in AGN jets.

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“…The RML image reconstruction algorithms in eht-imaging have been used in the analysis of EHT observations of M87 * (The Event Horizon Telescope Collaboration et al 2019dCollaboration et al , 2021b, Sgr A * (The Event Horizon Telescope Collaboration et al 2022c), 3C279 (Kim et al 2020), and Centaurus A (Janssen et al 2021). They have also been used in imaging VLBI data sets from other arrays at lower frequencies (e.g., Issaoun et al 2019Issaoun et al , 2021Savolainen et al 2021;Xu et al 2021;Zhao et al 2022).…”

Section: Implementation In Eht-imagingmentioning

confidence: 99%

Multifrequency Black Hole Imaging for the Next-generation Event Horizon Telescope

Chael

Issaoun

Pesce

et al. 2023

ApJ

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The Event Horizon Telescope (EHT) has produced images of the plasma flow around the supermassive black holes in Sgr A* and M87* with a resolution comparable to the projected size of their event horizons. Observations with the next-generation Event Horizon Telescope (ngEHT) will have significantly improved Fourier plane coverage and will be conducted at multiple frequency bands (86, 230, and 345 GHz), each with a wide bandwidth. At these frequencies, both Sgr A* and M87* transition from optically thin to optically thick. Resolved spectral index maps in the near-horizon and jet-launching regions of these supermassive black hole sources can constrain properties of the emitting plasma that are degenerate in single-frequency images. In addition, combining information from data obtained at multiple frequencies is a powerful tool for interferometric image reconstruction, since gaps in spatial scales in single-frequency observations can be filled in with information from other frequencies. Here we present a new method of simultaneously reconstructing interferometric images at multiple frequencies along with their spectral index maps. The method is based on existing regularized maximum likelihood (RML) methods commonly used for EHT imaging and is implemented in the eht-imaging Python software library. We show results of this method on simulated ngEHT data sets as well as on real data from the Very Long Baseline Array and Atacama Large Millimeter/submillimeter Array. These examples demonstrate that simultaneous RML multifrequency image reconstruction produces higher-quality and more scientifically useful results than is possible from combining independent image reconstructions at each frequency.

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RadioAstron discovers a mini-cocoon around the restarted parsec-scale jet in 3C 84

Cited by 6 publications

References 1 publication

Jet kinematics in the transversely stratified jet of 3C 84

Jet kinematics in the transversely stratified jet of 3C 84

Polarization Observations of AGN Jets: Past and Future

Multifrequency Black Hole Imaging for the Next-generation Event Horizon Telescope

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