PCA of the spectral energy distribution and emission line properties of red 2MASS AGN

TL;DR

This study uses principal component analysis on the spectral energy distributions and emission line properties of red 2MASS AGN to identify key factors like accretion rate and obscuration affecting their observed characteristics.

Contribution

It introduces a PCA-based approach to disentangle the effects of obscuration, host galaxy emission, and accretion rate in the spectral properties of red AGN.

Findings

Eigenvector 1 correlates with L/Ledd ratio and intrinsic absorption.

Eigenvector 2 relates to host galaxy emission.

Eigenvectors 3 and 4 distinguish between types of obscuration.

Abstract

We analyze the spectral energy distributions (SEDs) and emission line properties of the red (J-K$_S$ > 2) 2MASS AGN observed by Chandra using principle component analysis. The sample includes 44 low redshift AGN with low or moderate obscuration (N_H < 10^{23} cm^{-2}) as indicated by X-rays and SED modeling. The obscuration of the AGN allows us to see weaker emission components (host galaxy emission, AGN scattered light) which are usually outshone by the AGN. The first four eigenvectors explain 70% of the variance in the sample. The dominant cause of variance in the sample (eigenvector 1) is the L/Ledd ratio strengthened by intrinsic absorption. Eigenvector 2 is related to host galaxy (relative to the observed AGN) emission and eigenvectors 3 and 4 distinguish between two sources of obscuration: host galaxy absorption and circumnuclear absorption. Although our analysis is consistent with unification schemes where inclination dependent obscuration is important in determining the AGN SEDs, the L/Ledd ratio is the most important factor, followed by host galaxy emission.