Giant Metrewave Radio Telescope Observations of Head–Tail Radio Galaxies

Abstract

We present results from a study of seven large known head−tail radio galaxies based on observations using the Giant Metrewave Radio Telescope at 240 and 610 MHz. These observations are used to study the radio morphologies and distribution of the spectral indices across the sources. The overall morphology of the radio tails of these sources is suggestive of random motions of the optical host around the cluster potential. The presence of the multiple bends and wiggles in several head−tail sources is possibly due to the precessing radio jets. We find steepening of the spectral index along the radio tails. The prevailing equipartition magnetic field also decreases along the radio tails of these sources. These steepening trends are attributed to the synchrotron aging of plasma toward the ends of the tails. The dynamical ages of these sample sources have been estimated to be ∼10 8 yr, which is a factor of six more than the age estimates from the radiative losses due to synchrotron cooling.

A LOFAR view into the stormy environment of the galaxy cluster 2A0335+096

“…Under the assumption that each cell defines a cylindrical section of the tail with a radius of 22.5 kpc and height of 45 kpc (i.e., corresponding with the size of the sampling boxes) 7 and by using the flux density at 144 MHz measured in the first cell to normalize the model spectrum j(ξ), we can produce the expected flux density and spectral index profiles We compared the observed spectral index profile with extreme two predictions produced by assuming v gal = 960 and 1600 km s −1 . The first one is computed by assuming that the los velocity is 1/ √ 2 of the total velocity (Sebastian et al 2017), whereas the second one is an upper limit estimated by forcing the model to reproduce the spectral index decline within the first half of the tail. We note that both velocities are higher than the cluster velocity dispersion σ 600 km s −1 (calculated on the basis of the M 500 = 2.27 × 10 14 M and R 500 = 0.92 Mpc reported in Giacintucci et al 2017), which is not unusual for head-tail galaxies (e.g., Venkatesan et al 1994).…”

“…Interestingly, 2A0335+096 also hosts the head-tail radio galaxy GB6 B0335+096 (z = 0.038), an FR I galaxy (Fanaroff & Riley 1974) with an extended radio tail (Patnaik & Singh 1988;Sebastian et al 2017). Tailed FR I radio galaxies are characterized by large-scales, low-brightness emission bent by the environmental pressure (thermal or ram-pressure) in the same direction, forming structures similar to tails.…”

Tailed Radio Galaxies from the TIFR GMRT Sky Survey

“…(3) The differences in the ejection of jets with respect to the direction of motion of the host galaxy in the inter-cluster medium and environments, as well as projection effects, are responsible for the asymmetries found in the radio jets in some tailed radio galaxies (Sebastian et al 2017). ( 4) The probability of detection of tailed radio sources decreases in the clusters with less number of galaxies (Stocke 1977;Adams, Jensen & Stocke 1980).…”

High-resolution VLA low radio frequency observations of the Perseus cluster: radio lobes, mini-halo and bent-jet radio galaxies

“…To perform a spectral index analysis of both NGC 1265 and IC 310, we used Giant Metrewave Radio Telescope (GMRT) observations at 610 MHz of these two sources presented in Sebastian et al (2017). The calibrated measurement set was re-imaged with a θ FWHM = 15 resolution and a cell size of 3 , in order to get similar resolution to our B-configuration VLA 270-430 MHz radio map.…”

“…In order to study these spectral characteristics, we produced spectral index maps combining our B-configuration VLA observations (with effective frequency of 344 MHz) with the GMRT observations at an effective frequency of 610 MHz of NGC 1265 and IC 310 presented in Sebastian et al (2017). These maps are presented in Figure 11.…”