The Ubiquitous Radio Continuum Emission from the Most Massive Early-Type Galaxies

TL;DR

This study measures radio emissions from 396 bright early-type galaxies, revealing that the most massive ones consistently host active galactic nuclei or recent star formation, with radio power strongly correlated to their luminosity.

Contribution

It provides a comprehensive analysis of radio continuum emission in a large sample of early-type galaxies, establishing a strong luminosity-power relation and confirming persistent activity in the most massive galaxies.

Findings

Radio power spans 4 orders of magnitude at fixed luminosity.

Median radio power scales as luminosity to the 2.78 power.

All most massive galaxies show detectable radio emission.

Abstract

We have measured the radio continuum emission of 396 early-type galaxies brighter than K = 9, using 1.4 GHz imagery from the NRAO VLA Sky Survey, Green Bank 300-ft Telescope and 64-m Parkes Radio Telescope. For M_K < -24 early-type galaxies, the distribution of radio powers at fixed absolute magnitude spans 4 orders of magnitude and the median radio power is proportional to K-band luminosity to the power 2.78\pm0.16. The measured flux densities of M_K < -25.5 early-type galaxies are greater than zero in all cases. It is thus highly likely that the most massive galaxies always host an active galactic nucleus or have recently undergone star formation.