Non-thermal emission in lobes of radio galaxies – III. 3C 98, Pictor A, DA 240, Cygnus A, 3C 326, and 3C 236

Peršić, M.; Rephaeli, Yoel

doi:10.1093/mnras/stz3415

Monthly Notices of the Royal Astronomical Society

2019

DOI: 10.1093/mnras/stz3415

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Non-thermal emission in lobes of radio galaxies – III. 3C 98, Pictor A, DA 240, Cygnus A, 3C 326, and 3C 236

M. Peršić

Yoel Rephaeli

Abstract: Recent analyses of the broad spectral energy distributions (SED) of extensive lobes of local radio-galaxies have confirmed the leptonic origin of their Fermi/LAT γ-ray emission, significantly constraining the level of hadronic contribution. SED of distant (D L > 125 Mpc) radio-galaxy lobes are currently limited to the radio and X-ray bands, hence give no information on the presence of non-thermal (NT) protons but are adequate to describe the properties of NT electrons. Modeling lobe radio and X-ray emission in… Show more

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The dying accretion and jet in a powerful radio galaxy of Hercules A

Feng

et al. 2020

Res. Astron. Astrophys.

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Hercules A (Her A) is one of a rare class of dying and transition-type objects, which has a pair of giant, powerful radio lobes and a weak radio core. We reduce and analyze the radio data of Her A that were observed by the Expanded Very Large Array (EVLA) during 2010-2011 at C band. The intensity distribution is very smooth along the edge of the lobe front and the intensity also sharply decreases at the edge, which supports that magnetic fields may play an important role in radio lobes. The spectrum of the weak core is very steep and the core flux becomes weaker by about ten percent when compared to what was observed twenty years ago, which suggest that the central engine is still dying quickly. Her A deviates a lot from the relation between [O III] luminosity and low-frequency 178 MHz luminosity (L O III – L 178MHz) as defined by other FR I/II sources. However, when only radio core emission is considered, it roughly follows an L O III – L 178 MHz correlation. This result supports that the black-hole accretion and large-scale jet in Her A did not evolve simultaneously, and indicates that although the large-scale jet is still powerful, the accretion and inner jet have changed into an inactive state. Based on the estimated Bondi accretion rate, we model the spectrum of Her A with a radiatively inefficient accretion flow and jet model.

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The dying accretion and jet in a powerful radio galaxy of Hercules A

Feng

et al. 2020

Res. Astron. Astrophys.

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On the significance of relativistically hot pairs in the jets of FR II radio galaxies

Sikora

Nalewajko

Madejski

2020

Monthly Notices of the Royal Astronomical Society

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The energetic composition of radio lobes in the FR II galaxies — estimated by comparing their radio luminosities with the powers required to inflate cavities in the external medium — seems to exclude the possibility of their energetic domination by protons. Furthermore, if the jets were dominated by the kinetic energy of cold protons, it would be difficult to efficiently accelerate leptons in the jets’ terminal shocks. Assuming that the relative energy contents of leptons, protons and magnetic fields are preserved across the shocks, the above implies that the large-scale jets should also be energetically dominated by leptons: Pe, j ≳ Pp, j. On the other hand, previous studies of small-scale jets in blazars and radio cores suggest a pair content (number of electrons and positrons per proton) of the order of ne/np ∼ 20. Assuming further that the particle composition of jets does not evolve beyond the blazar scales, we show that this implies an average random Lorentz factor of leptons in large-scale jets of $\bar{\gamma }_{\rm e,j} \gtrsim 70(1+\chi _{\rm p})(20n_{\rm p}/n_{\rm e})$, and that the protons should be mildly relativistic with χp ≡ (εp + pp)/ρpc2 ≲ 2, pp the pressure of protons, εp the internal energy density of protons, and ρpc2 the rest-mass energy density of protons. We derive the necessary conditions for loading the inner jets by electron-positron pairs and proton-electron plasma, and provide arguments that heating of leptons in jets is dominated by magnetic reconnection.

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Echoes of the past: ultra-high-energy cosmic rays accelerated by radio galaxies, scattered by starburst galaxies

Bell

Matthews

2022

Monthly Notices of the Royal Astronomical Society

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We explore the possibility that the hotspot of ultrahigh energy cosmic rays (UHECR) detected by the Telescope Array (TA) from the approximate direction of M82 and the M81 group of galaxies might be the echo of UHECR emitted by Centaurus A in an earlier more powerful phase. Echoes from other starburst galaxies or groups of galaxies may contribute to the UHECR flux at the Earth. We use an illustrative Monte Carlo model of mono-energetic UHECR transport by small angle scattering to generate synthetic sky maps. The model informs a discussion of overall energetics and time and distance scales. We find a viable echo model for the observed UHECR hotspots if the UHECR luminosity of Centaurus A 20 Myr ago was 200 times its present luminosity and if the ordered magnetic field exceeds 10-20nG out to a distance of 400-800kpc in the circumgalactic medium of M82 and other starburst galaxies.

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Non-thermal emission in lobes of radio galaxies – III. 3C 98, Pictor A, DA 240, Cygnus A, 3C 326, and 3C 236

Cited by 5 publications

References 50 publications

The dying accretion and jet in a powerful radio galaxy of Hercules A

The dying accretion and jet in a powerful radio galaxy of Hercules A

On the significance of relativistically hot pairs in the jets of FR II radio galaxies

Echoes of the past: ultra-high-energy cosmic rays accelerated by radio galaxies, scattered by starburst galaxies

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