Optical spectroscopy of 3CR sample of radio sources at z<0.3

TL;DR

This study conducts optical spectroscopy on a complete sample of 3CR radio sources at z<0.3, classifying AGNs based on spectral features and revealing diverse accretion states and recently inactive nuclei.

Contribution

It provides a comprehensive optical spectral classification of 3CR radio sources, linking spectral types to radio properties and revealing new insights into AGN activity states.

Findings

Sources classified as HEG, LEG, and 'Relic' AGNs based on spectra.

Different spectral types follow distinct optical-radio correlations.

'Reclig' AGNs show signs of recently turned-off activity.

Abstract

We are carrying out a program of optical spectroscopy of the complete subsample of the 3CR catalog of radio sources at redshift z < 0.3. The sample consists of 113 3CR sources, comprising FR I, FR II radio galaxies and Quasars. Complete datasets in other bands are already or will be soon available for the whole sample but the optical spectra are sparse and inhomogeneous in quality. The observations are carried out at the 3.58m Telescopio Nazionale Galileo (TNG, La Palma). More than 100 sources have been already observed. We present here the preliminary results on the analysis of the high and low resolution spectra. We found that sources can be spectroscopically characterized as: High Excitation Galaxies (HEG), Low Excitation Galaxies (LEG) and "Relic" AGNs. This classification is supported by the optical - radio correlations in which objects spectroscopically different follow different correlations. We conclude that AGNs with the same radio power can be fueled with different accretion properties. "Relic" radio-galaxies are characterized by extreme low excitation spectra that we interpret as nuclei whose activity has recently turned-off. The full spectral catalog will be made available to the scientific community.