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arXiv 1302.0850astro-ph.HEastro-ph.GA
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用Swift BAT研究GOALS LIRGs中AGN的微弱超硬X射线发射

Studying Faint Ultra Hard X-ray Emission from AGN in GOALS LIRGs with Swift BAT

Michael Koss, Richard Mushotzky, Wayne Baumgartner, Sylvain Veilleux, Jack Tueller, Craig Markwardt, Caitlin M. Casey

摘要:

我们提出了第一个分析的全天空雨燕BAT超硬X射线(14-195千电子伏)数据的目标列表的对象。我们发现BAT数据可以在比以前的盲检测目录更弱的3倍限制下进行研究,这些盲检测目录基于源位置的先验知识,并使用较小的能量范围进行源检测。我们从GOALS样品中测定了134个附近(z<0.05)亮红外星系(LIRGS)的活动星系核分数。我们发现LIRGs在14-195 keV和24-35 keV的能量范围内比在恒星质量和红移上匹配的星系有更高的探测频率。与其他波段的工作一致,活动星系核的探测率在高红外光度下显著增加,高光度LIRGs的一半(50%,6/12,log L_IR/L_sun>11.8)被探测到。BAT AGN分类显示97%(37/38)的协议与钱德拉和XMM AGN分类使用硬度比或铁K-α线的检测。这证实了我们的统计分析,并支持使用雨燕BAT全天巡天研究超硬X射线波段任何类别源的较暗群体。LIRG中的BAT活动星系核倾向于显示出更高的柱密度,40 \pm 9%显示出14-195 keV/2-10 keV的硬度通量比,这表明柱密度很高或康普顿厚度(log N_H>24 cm^-2),而非LIRG BAT活动星系核只有12 \pm 5%。我们还发现,使用特定的能量范围的BAT探测器可以产生额外的源超过总频带检测与24%(5/21)的检测LIRG在24-35 keV未检测到在14-195 keV。

英文摘要:

We present the first analysis of the all-sky Swift BAT ultra hard X-ray (14-195 keV) data for a targeted list of objects. We find the BAT data can be studied at 3x fainter limits than in previous blind detection catalogs based on prior knowledge of source positions and using smaller energy ranges for source detection. We determine the AGN fraction in 134 nearby (z<0.05) luminous infrared galaxies (LIRGS) from the GOALS sample. We find that LIRGs have a higher detection frequency than galaxies matched in stellar mass and redshift at 14-195 keV and 24-35 keV. In agreement with work at other wavelengths, the AGN detection fraction increases strongly at high IR luminosity with half of high luminosity LIRGs (50%, 6/12, log L_IR/L_sun>11.8) detected. The BAT AGN classification shows 97% (37/38) agreement with Chandra and XMM AGN classification using hardness ratios or detection of a iron K-alpha line. This confirms our statistical analysis and supports the use of the Swift BAT all-sky survey to study fainter populations of any category of sources in the ultra hard X-ray band. BAT AGN in LIRGs tend to show higher column densities with 40\pm9% showing 14-195 keV/2-10 keV hardness flux ratios suggestive of high or Compton-thick column densities (log N_H>24 cm^-2), compared to only 12\pm5% of non-LIRG BAT AGN. We also find that using specific energy ranges of the BAT detector can yield additional sources over total band detections with 24% (5/21) of detections in LIRGs at 24-35 keV not detected at 14-195 keV.

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