A statistical study of SDSS radio-emitters

TL;DR

This study analyzes the relationship between radio and optical properties of galaxies using SDSS and FIRST data, revealing that powerful radio galaxies are primarily driven by nuclear activity, with classifications supporting AGN dominance.

Contribution

It provides a large-scale statistical analysis linking radio emission ratios to optical emission line diagnostics, clarifying the nuclear origin of radio emission in galaxies.

Findings

Radio-optical correlation indicates nuclear activity as the emission source.

Spectroscopic classifications align with radio emission strength, confirming AGN dominance.

Most LINERs are confirmed as AGN-powered, with some powered by post-AGB stars.

Abstract

The cross-correlation of the Sloan Digital Sky Survey Data Release 7 with the Faint Images of the Radio Sky at Twenty-Centimeters survey allows for a multiwavelength statistical study of radio-optical galaxy properties on a very large number of sources. The correlation we find between $L_{[20 cm]}/L_{[H\alpha]}$ and optical emission line ratios suggests that the origin of the emission in powerful radio-galaxies is of nuclear rather than of stellar origin. In particular, the spectroscopic classification in Seyferts, Low Ionization Narrow Emission Regions (LINERs) and star-forming galaxies provided by emission-line diagnostic diagrams peaks on the AGN region for higher $L_{[20 cm]}/L_{[H\alpha]}$ values. The trend differs from Seyferts to LINERs. The [NII]/H$\alpha$ vs. equivalent width of the H$\alpha$ line diagram confirms the LINER classification for most of those that have been identified with the traditional diagnostic diagrams. A small fraction of sources seem to be powered by post-AGB stars instead.