The mm-wave compact component of AGN

TL;DR

This study uses 100 GHz observations to explore the compact mm-wave emission in AGN, revealing a correlation with X-ray luminosity and suggesting a common coronal origin for radio and X-ray emissions.

Contribution

First to report 100 GHz observations of a sample of AGN, showing mm emission originates from smaller scales and correlates with X-ray luminosity, indicating a potential common origin.

Findings

Most AGN detected at 100 GHz with flux excess over low-frequency extrapolation.

MM emission likely from smaller scales than GHz emission.

MM luminosity correlates with X-ray luminosity, hinting at a shared coronal origin.

Abstract

mm-wave emission from Active Galactic Nuclei (AGN) may hold the key to understanding the physical origin of their radio cores. The correlation between radio/mm and X-ray luminosity may suggest a similar physical origin of the two sources. Since synchrotron self absorption decreases with frequency, mm-waves probe smaller length scales than cm-waves. We report on 100 GHz (3 mm) observations with CARMA of 26 AGNs selected from the hard X-ray Swift/BAT survey. 20/26 targets were detected at 100 GHz down to the 1 mJy (3 $\sigma$) sensitivity, which corresponds to optically thick synchrotron source sizes of 10$^{-4}$ - 10$^{-3}$ pc). Most sources show a 100 GHz flux excess with respect to the spectral slope extrapolated from low frequencies. This mm spectral component likely originates from smaller scales than the few-GHz emission. The measured mm sources lie roughly around the L$_{mm}$ (100 GHz) $\sim$ 10$^{-1}$ L$_{X}$ (2-10 keV) relation, similar to a few previously published X-ray selected sources, and hinting perhaps at a common coronal origin.