Correlations of the IR Luminosity and Eddington Ratio with a Hard X-ray Selected Sample of AGN

TL;DR

This study investigates the correlations between hard X-ray luminosity, near-infrared nuclear luminosity, and Eddington ratio in a large, unbiased sample of active galactic nuclei, revealing significant relationships that inform models of AGN emission.

Contribution

It provides the first large, unbiased analysis of correlations between X-ray, near-IR luminosities, and Eddington ratio in AGN, offering new constraints for emission models.

Findings

Near-IR nuclear luminosity correlates with hard X-ray luminosity over three orders of magnitude.

Eddington ratio is proportional to X-ray luminosity in AGN.

The IR-X-ray correlation is unlikely due to dust emission.

Abstract

We use the SWIFT Burst Alert Telescope (BAT) sample of hard x-ray selected active galactic nuclei (AGN) with a median redshift of 0.03 and the 2MASS J and K band photometry to examine the correlation of hard x-ray emission to Eddington ratio as well as the relationship of the J and K band nuclear luminosity to the hard x-ray luminosity. The BAT sample is almost unbiased by the effects of obscuration and thus offers the first large unbiased sample for the examination of correlations between different wavelength bands. We find that the near-IR nuclear J and K band luminosity is related to the BAT (14 - 195 keV) luminosity over a factor of $10^3$ in luminosity ($L_{IR} \approx L_{BAT}^{1.25}$)and thus is unlikely to be due to dust. We also find that the Eddington ratio is proportional to the x-ray luminosity. This new result should be a strong constraint on models of the formation of the broad band continuum.