The MURALES survey

VI. Properties and origin of the extended line emission structures in radio galaxies

¹ INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese, Italy
e-mail: barbara.balmaverde@inaf.it
² INAF – Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy
³ Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
⁴ Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21210, USA
⁵ Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
⁶ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
⁷ Dipartimento di Fisica, Università degli Studi di Torino, Via Pietro Giuria 1, 10125 Torino, Italy
⁸ European Southern Observatory, Alonso de Còrdova 3107, Vitacura, Regiòn Metropolitana, Chile
⁹ Istituto Nazionale di Fisica Nucleare, Sezione di Torino, 10125 Torino, Italy
¹⁰ Dipartimento di Fisica e Astronomia, Università di Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, Firenze, Italy
¹¹ INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
¹² University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
¹³ Instituto de Astrofìsica de Canarias, Calle Vìa Làctea, s/n, 38205 La Laguna, Tenerife, Spain
¹⁴ Departamento de Astrofìsica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
¹⁵ Instituto de Astrofìsica, Facultad de Fìsica, Pontificia Universidad Catòlica de Chile, Casilla 306, Santiago 22, Chile

Received: 3 December 2021
Accepted: 14 March 2022

Abstract

This is the sixth paper presenting the results of the MUse RAdio Loud Emission line Snapshot survey. We observed 37 radio sources from the 3C sample with z < 0.3 and a declination < 20° with the Multi Unit Spectroscopic Explorer optical integral field spectrograph at the Very Large Telescope. Here, we focus on the properties of the extended emission line regions (EELRs) that can be studied with unprecedented detail thanks to the depth of these observations. Line emission in the ten FR Is is, in most cases, confined to within ≲4kpc, while large-scale (≳4 kpc) ionized gas is seen in all but two of the 26 FR IIs. It usually takes the form of elongated or filamentary structures, typically extending between 10 and 30 kpc, but also reaching distances of ∼80 kpc. We find that the large-scale ionized gas structures show a tendency to be oriented at large angles from the radio axis, and that the gas on a scale of a few kiloparsecs from the nucleus often shows ordered rotation with a kinematical axis forming a median angle of 65° with the radio axis. We also discuss the velocity field and ionization properties of the EELRs. The observed emission line structures appear to be associated with gaseous “superdisks” that formed after a gas-rich merger. The different properties of the EELR can be explained with a combination of the source evolutionary state and the orientation of the superdisk with respect to the radio axis. The general alignment between the superdisks and radio axis might be produced by stable and coherent accretion maintained over long timescales.