Viewing Classical Radio Galaxies with the Upgraded GMRT and MeerKAT—A Progress Report

Dharam V Lal,Sphesihle Makhathini,Marco Bondi,Dane Kleiner,Tiziana Venturi,Gyula I G Józsa,Portia Legodi,Landman H Bester,Sarah V White,Francesca Loi,Kshitij Thorat,Bernie Fanaroff,Oleg M Smirnov

doi:10.3390/galaxies9040087

Abstract

We present a progress report of a study of FR I and FR II radio galaxies. Several new morphological features in the radio emission are now revealed using the high (μJy) sensitivity reached in the range 550–1712 MHz, more than a factor of three, at the high (∼4″−7″) angular resolution with the upgraded Giant Metrewave Radio Telescope (uGMRT) and MeerKAT. Therefore, the aim of this study is to understand if we need to revise our current classification scheme for classical radio galaxies. In order to address our goals, we have carefully constructed a sample of 14 (6 FR I, 6 FR II and 2 FR 0) radio galaxies. The uGMRT and MeerKAT images of our four target sources revealed a wealth of morphological details, e.g., filamentary structure in the emission from the lobes, misalignments, radio emission beyond the hot-spots in three sources, etc.; see Fanaroff et al. (2021). Here, we present preliminary results for two more radio galaxies from our sample using uGMRT, in the light of the local environment. Finally, we are awaiting uGMRT and MeerKAT observations of remaining sample sources. Our results show that for the radio galaxies in this study, the morphological classification scheme for the classical FR I/FR II radio galaxies still holds, even with the improved imaging capabilities of the uGMRT and MeerKAT. Furthermore, we need to be cautious when using automated procedures for classification schemes, e.g., in surveys (with poorer sensitivities and angular resolutions) because of the rich morphological details that are shown in our uGMRT and MeerKAT images.

Highlights

It will soon be 50 years since the publication of the paper: The morphology of extragalactic radio sources of high and low luminosity, Fanaroff & Riley [1]
We have summarized the results presented in Fanaroff et al [28] for the upgraded Giant Metrewave Radio Telescope (uGMRT) and MeerKAT images of four radio galaxies belonging to a larger sample of 14
FR I, 6 FR II and 2 FR 0) radio galaxies that are carefully selected with well defined selection criteria that cover a frequency range from 550 MHz to 1712 MHz, more than a factor of three, providing radio images at nearly identical angular resolutions and sensitivities

Summary

Introduction

It will soon be 50 years since the publication of the paper: The morphology of extragalactic radio sources of high and low luminosity, Fanaroff & Riley [1]. Several radio galaxies (e.g., Centaurus A, M 87, NGC 1275, etc.) have been well studied in radio, infrared, optical, X-ray, and γ-rays (e.g., Centaurus A: [3,4,5]) They have been detected from radio to TeV γ-rays, and have been studied as high-nutrino and ultra-high energy cosmic-ray potential emitters [6]. These studies propose a leptonic and hadronic model to explain the broadband spectral energy distribution spectrum in them (see [7] and references therein)

Objectives

Results

Conclusion