Large-scale environment of FR 0 radio galaxies

¹ INAF-Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese, Italy
e-mail: capetti@oato.inaf.it
² Dipartimento di Fisica, Università degli Studi di Torino, Via Pietro Giuria 1, 10125 Torino, Italy
³ Istituto Nazionale di Fisica Nucleare, Sezione di Torino, 10125 Torino, Italy
⁴ Consorzio Interuniversitario per la Fisica Spaziale, Via Pietro Giuria 1, 10125 Torino, Italy
⁵ Department of Physics and Astronomy, University of Southampton, Highfield SO17 1BJ, UK

Received: 27 May 2019
Accepted: 29 November 2019

Abstract

We explore the properties of the large-scale environment of the sources in the Faranoff-Riley class 0 catalog (FR0CAT). This sample includes 104 compact radio sources that are associated with nearby (z <  0.05) early-type galaxies. Using various estimators, we find that FR 0s are located in regions with higher than the average number of galaxies. The average galaxies density around FR 0s is a factor two lower with respect to FR I radio galaxies. This latter difference is driven by the large fraction (63%) of FR 0s that are located in groups formed by fewer than 15 galaxies. FR Is rarely (17%) inhabit an environment like this. In addition to the lack of substantial extended radio emission that defines the FR 0 class, this is the first significant difference between the properties of these two populations of low-power radio galaxies. We interpret the differences in environment between FR 0s and FR Is as due to an evolutionary link between local galaxies density, black hole spin, jet power, and extended radio emission.