Radio and X-ray Observations of the Restarted Radio Galaxy in the Galaxy Cluster CL 0838+1948

Abstract

We present VLA Low-band Ionosphere and Transient Experiment (VLITE) 338 MHz observations of the galaxy cluster CL 0838+1948. We combine the VLITE data with Giant Metrewave Radio Telescope 610 MHz observations and survey data. The central galaxy hosts a 250 kpc source whose emission is dominated by two large lobes at low frequencies. At higher frequencies, a pair of smaller lobes (∼30 kpc) is detected within the galaxy optical envelope. The observed morphology is consistent with a restarted radio galaxy. The outer lobes have a spectral index αout=1.6, indicating that they are old, whereas the inner lobes have αinn=0.6, typical for an active source. Spectral modeling confirms that the outer emission is a dying source whose nuclear activity switched off not more than 110 Myr ago. Using archival Chandra X-ray data, we compare the radio and hot gas emission. We find that the active radio source is contained within the innermost and X-ray brightest region, possibly a galactic corona. Alternatively, it could be the remnant of a larger cool core whose outer layers have been heated by the former epoch of activity that has generated the outer lobes.

The Dynamics and Energetics of Remnant and Restarting RLAGN

“…The source B2 0924 + 30 is another well studied source considered to be a prototypical and genuine remnant; it has steep spectral indices with α 1.0 at frequencies below 1 GHz [34,40], an upper-limit core luminosity five orders of magnitude below that of the strongest core-dominated RLAGN and which is two orders of magnitude below the core luminosity expected from the core-total luminosity relation for elliptical galaxies (e.g., [23]). With broad-band spectral aging analysis using maps at an angular resolution of 147 arcsec [41], the source has a pronounced integrated spectral steepening beyond 2 GHz, an average spectral age of 50 +12 −11 Myr (since last particle acceleration, consistent with the more robust modelling by [42]), and a maximum spectral age of the particle population of 90 +30 −30 Myr, similar to the derived spectral ages of other remnant lobes (e.g., B0917 + 75, 100 Myr; [43], J1324-3138, 97 Myr; [44], CL 0838 + 1948, 110 Myr; [45]).…”

New Window on the Radio Emission from Galaxies, Clusters and Cosmic Web—Conference Summary

“…The outer emission is made by old plasma ejected no more than 110 Myr ago. Using archival Chandra X-ray data, they found that the active radio source is contained within the innermost and brightest X-ray region [7].…”

Barbell-shaped giant radio galaxy with ∼100 kpc kink in the jet

“…We assume a γ min of 100 to estimate B eq (e.g. Isobe & Koyama 2015;Giacintucci et al 2021). The quantity k represents the ratio of energies in relativistic protons to electrons (1 or 100), I 0 is the surface brightness at the measuring frequency, and d is the mean of the major and minor axes (source depth).…”