ULIRG IRAS19254-7245的Suzaku观察：揭示AGN组分
A Suzaku observation of the ULIRG IRAS19254-7245: disclosing the AGN component
摘要：
我们在这里讨论的是朱雀星对IRAS 19254-7245（也称为超天线）的长期观测，它是本地宇宙中最亮和研究最充分的超亮红外星系之一。这一长时间的观测首次探测到了10 keV以上的IRAS 19254-7245，并测量到15-30 keV的通量约为5 × 10 ^（-12）erg cm^-2 s^-1。10 keV以上的探测使我们首次揭示了IRAS 19254-7245中活动星系核的内禀光度，它被强烈吸收（Nh ~ 3 × 10 ^（24）cm^-2），并具有类星体区域内的内禀光度（L（2-10 keV）~ 3 × 10^（44）erg s^-1）。IRAS 19254-7245的2-10 keV光谱非常硬（γ ~1.2），并呈现出强的铁谱线（EW ~0.7 keV），这清楚地表明，在10 keV以下，我们只能看到再处理的辐射。由于Fe-K辐射的能量约为6.7 keV，与类He Fe一致，并且其EW太高，不能用星爆主导的情景来解释，我们认为IRAS 19254-7245的2- 10 keV辐射主要是由高度电离物质的反射/散射所决定的。事实上，在后一种情况下，我们发现照明源的光子指数为Gamma=1.87（+0.11，-0.28），与射电宁静无遮蔽活动星系核的平均值非常一致。
英文摘要：
We discuss here a long Suzaku observation of IRAS 19254-7245 (also known as the Superantennae), one of the brightest and well studied Ultra Luminous Infrared Galaxies in the local Universe. This long observation provided the first detection of IRAS 19254-7245 above 10 keV, and measured a 15-30 keV flux of ~5x10^(-12) erg cm^-2 s^-1. The detection above 10 keV has allowed us to unveil, for the first time, the intrinsic luminosity of the AGN hosted in IRAS 19254-7245, which is strongly absorbed (Nh ~ 3x10^(24) cm^-2) and has an intrinsic luminosity in the QSO regime (L(2-10 keV) ~ 3 x 10^(44) erg s^-1). The 2-10 keV spectrum of IRAS 19254-7245 is remarkably hard (Gamma~1.2), and presents a strong iron line (EW ~0.7 keV), clearly suggesting that below 10 keV we are seeing only reprocessed radiation. Since the energy of the Fe K emission is found to be at ~6.7 keV, consistent with He-like Fe, and its EW is too high to be explained in a starburst dominated scenario, we suggest that the 2--10 keV emission of IRAS 19254-7245 is dominated by reflection/scattering from highly ionized matter. Indeed, within this latter scenario we found that the photon index of the illuminating source is Gamma=1.87 (+0.11,-0.28), in excellent agreement with the mean value found for radio quiet unobscured AGN.
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