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

Abstract

We present RadioAstron space-based very long baseline interferometry (VLBI) observations of the nearby radio galaxy 3C84 (NGC1275) at the centre of the Perseus cluster. The observations were carried out on September 21-22, 2013 and involved a global array of 24 ground radio telescopes observing at 5 GHz and 22 GHz, together with the Space Radio Telescope (SRT). Furthermore, the Very Long Baseline Array (VLBA) and the phased Very Large Array (VLA) observed the source quasi-simultaneously at 15 GHz and 43 GHz. Fringes between the ground array and the SRT were detected on baseline lengths up to 8.1 times the Earth's diameter, providing unprecedented resolution for 3C 84 at these wavelengths. We note that the corresponding fringe spacing is 125 microarcsec at 5 GHz and 27 microarcsec at 22 GHz. Our space-VLBI images reveal a previously unseen sub-structure inside the compact 1 pc long jet that was ejected about ten years earlier. In the 5 GHz image, we detected, for the first time, low-intensity emission from a cocoon-like structure around the restarted jet. Our results suggest that the increased power of the young jet is inflating a bubble of hot plasma as it carves its way through the ambient medium of the central region of the galaxy. Here, we estimate the minimum energy stored in the mini-cocoon, along with its pressure, volume, expansion speed, and the ratio of heavy particles to relativistic electrons, as well as the density of the ambient medium. About half of the energy delivered by the jet is dumped into the mini-cocoon and the quasi-spherical shape of the bubble suggests that this energy may be transferred to a significantly larger volume of the interstellar medium than what would be accomplished by the well-collimated jet on its own. The pressure of the hot mini-cocoon also provides a natural explanation for the almost cylindrical jet profile seen in the 22 GHz RadioAstron image.

To be published in Astronomy & Astrophysics

References in corpus (20)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• Heating Hot Atmospheres with Active Galactic Nuclei
• MOJAVE: Monitoring of Jets in AGN with VLBA Experiments. V. Multi-epoch VLBA Images
• RadioAstron -- a Telescope with a Size of 300 000 km: Main Parameters and First Observational Results
• Imaging the Schwarzschild-radius-scale Structure of M87 with the Event Horizon Telescope using Sparse Modeling
• A numerical simulation of the evolution and fate of a FRI jet. The case of 3C 31
• Event Horizon Telescope observations of the jet launching and collimation in Centaurus A
• On the spine-layer scenario for the very high-energy emission of NGC 1275
• Discovery of a new subparsec counterjet in NGC 1275: the inclination angle and the environment
• Large-scale jets from active galactic nuclei as a source of ICM heating: cavities and shocks
• Spurious source generation in mapping from noisy phase-self-calibrated data
• Enhanced Polarized Emission from the One-Parsec-Scale Hotspot of 3C 84 as a Result of the Interaction with Clumpy Ambient Medium
• TXS 0128+554: A Young Gamma-Ray Emitting AGN With Episodic Jet Activity
• Pinpointing the jet apex of 3C 84
• Radio mode feedback: Does relativity matter?
• A multiband study and exploration of the radio wave - $\gamma$-ray connection in 3C 84
• Sub-milliarcsecond imaging of a bright flare and ejection event in the extragalactic jet 3C 111
• Jet propagation through inhomogeneous media and shock ionization

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• Discovery of Limb Brightening in the Parsec-scale Jet of NGC 315 through Global Very Long Baseline Interferometry Observations and Its Implications for Jet Models
• Observational Evidence to Support a Dense Ambient Medium Shaping the Jet in 3C 84
• Revealing a ribbon-like jet in OJ 287 with RadioAstron
• Evolution, speed, and precession of the parsec-scale jet in the 3C 84 radio galaxy
• Revisiting 3C 279 jet morphology with space VLBI at 26 microarcsecond resolution
• Direct VLBI Detection of Interstellar Turbulence Imprint on a Quasar: TXS 2005+403
• Where within the 3C 84 jet are $\gamma$-rays produced?