The Spectral Energy Distributions of Red Two Micron All Sky Survey Active Galactic Nuclei

Abstract

We present infrared (IR) to X-ray spectral energy distributions (SEDs) for 44 red active galactic nuclei (AGNs) selected from the Two Micron All Sky Survey (2MASS) survey on the basis of their red J – K_S color (>2 mag) and later observed by Chandra. In comparison with optically-, radio-, and X-ray-selected AGNs, their median SEDs are red in the optical and near-IR (NIR) with little/no blue bump. Comparison of the various broadband luminosity ratios shows that the main differences lie at the blue end of the optical and in the NIR to far-IR ratios (when available), with the red 2MASS AGNs being redder than the other samples. It thus seems that NIR color selection isolates the reddest subset of AGNs that can be classified optically. The shape of the SEDs is generally consistent with modest absorption by gas (in the X-ray) and dust (in the optical-IR), as demonstrated by comparing the optical and NIR colors with a reddened median SED and observed optical+NIR to intrinsic X-ray ratios. The levels of obscuration, estimated from X-rays, far-IR, and our detailed optical+NIR color modeling, are all consistent implying N_H ≤ few × 10^(22) cm^(–2). We present SED models that show how the AGN optical/NIR colors change due to differing amounts of reddening, AGN to host galaxy ratio, redshift, and scattered light emission, and apply them to the sources in the sample. We find that the 2MASS AGN optical color, B – R, and to a lesser extent the NIR color, J – K_S , are strongly affected by reddening, host galaxy emission, redshift, and in few, highly polarized objects also by scattered AGN light (<2% of intrinsic AGN light in the R band is scattered; this contribution becomes significant as the direct AGN light is absorbed). The lack of low equivalent widths in the distribution of the [O III] λ5007 emission line implies a predominance of inclined objects in the red 2MASS sample. The obscuration/inclination of the AGN allows us to see weaker emission components which are generally swamped by the AGN.