Radio galaxies of the local universe: all-sky catalog, luminosity functions, and clustering

TL;DR

This paper presents the first all-sky catalog of local radio galaxies, analyzes their luminosity functions and clustering, and finds a strong environmental influence on jet formation, aiding understanding of black hole feedback and cosmic rays.

Contribution

It introduces a new, comprehensive all-sky catalog of local radio galaxies with an automated matching algorithm, enabling detailed studies of their properties and environment.

Findings

Over 30% of cataloged galaxies are newly identified radio sources.

Radio galaxies are found in denser environments than similar non-radio galaxies.

Clustering analysis suggests environment influences jet formation, independent of black hole mass.

Abstract

To understand the feedback of black holes on their environment or the acceleration of ultra-high energy cosmic rays in the present cosmic epoch, a systematic, all-sky inventory of radio galaxies in the local universe is needed. Here we present the first catalog of radio-emitting galaxies that meets this requirement. Our catalog allows the selection of volume-limited subsamples containing all low-power radio galaxies, similar to the prototypical low-power radio galaxies Cen A or M87, within some hundred Mpc. It is constructed by matching radio emission from the NVSS and SUMSS surveys to galaxies of the 2MASS Redshift Survey (2MRS) using an image-level algorithm that properly treats the extended structure of radio sources. The sample contains 575 radio-emitting galaxies with a flux greater than 213 mJy at 1.4 GHz. Over 30% of the galaxies in our catalog are not contained in existing large-area extra-galactic radio samples. We compute the optical and radio luminosity functions and the fraction of radio galaxies as a function of galaxy luminosity. We find that the galaxy density around radio galaxies is significantly higher than around non-radio galaxies of the same luminosity and morphology. This enhanced clustering suggests a causal relation between external galaxy properties, such as environment or merger history, and the formation of powerful jets in the present universe. Since the enhancement is observed with respect to galaxies of the same luminosity and Hubble type, it is not primarily driven by black hole mass. Our automated matching procedure is found to select radio-emitting galaxies with high efficiency (99%) and purity (91%), which is key for future processing of deeper, larger samples.