Spitzer Observations of Powerful Radio Sources

TL;DR

This study uses Spitzer Space Telescope data to compare mid-infrared emissions from powerful radio galaxies and quasars, revealing differences due to non-thermal emission and dust absorption.

Contribution

It provides the first unbiased mid-infrared comparison of radio galaxies and quasars, quantifying the roles of non-thermal emission and dust absorption.

Findings

Quasars are four times brighter than radio galaxies at 15 microns.

Half of the brightness difference is due to non-thermal emission in quasars.

The other half is consistent with dust absorption in radio galaxies.

Abstract

We have measured the mid-infrared radiation from an orientation-unbiased sample of powerful 3C RR galaxies and quasars using the IRS and MIPS instruments aboard the Spitzer Space Telescope. We fit the Spitzer data as well as other measurements from the literature with synchrotron and dust components. At 15 microns, quasars are typically four times brighter than radio galaxies with the same isotropic radio power. Based on our fits, half of this difference can be attributed to the presence of non-thermal emission in the quasars but not the radio galaxies. The other half is consistent with dust absorption in the radio galaxies but not the quasars.