XMM‐Newton Observations of Red AGNs

Abstract

XMM-Newton spectra of five red 2MASS active galactic nuclei (AGNs),selected from a sample observed by Chandra to be relatively X-ray brightand to cover a range of hardness ratios, confirm the presence ofsubstantial absorbing material in three sources with opticalclassifications ranging from type 1 to type 2. A flat (hard) power-lawcontinuum is observed in the other two. The combination of X-rayabsorption and broad optical emission lines suggests either a small(nuclear) absorber or a favored viewing angle so as to cover the X-raysource but not the broad emission-line region (BELR). A soft excess isdetected in all three type 1 sources. We speculate that this may arisein an extended region of ionized gas, perhaps linked to the polarized(scattered) optical light present in these sources. The spectralcomplexity revealed by XMM-Newton emphasizes the limitations of thelow-S/N Chandra data. The new results strengthen our earlier conclusionsthat the observed X-ray continua of red AGNs are unusually hard atenergies >~2 keV. Their observed spectra are consistent withcontributing significantly to the missing hard or absorbed population ofthe cosmic X-ray background (CXRB), although their intrinsic power-lawslopes are typical of broad-line (type 1) AGNs (Γ~1.7-1.9). Thissuggests that the missing X-ray-absorbed CXRB population may includetype 1 AGNs or QSOs in addition to the type 2 AGNs generally assumed.