Shedding Light on the Compton-thick Active Galactic Nucleus in the Ultraluminous Infrared Galaxy UGC 5101 with Broadband X-Ray Spectroscopy
Shedding Light on the Compton-thick Active Galactic Nucleus in the Ultraluminous Infrared Galaxy UGC 5101 with Broadband X-Ray Spectroscopy
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DOI：
10.3847/1538-4357/835/2/179
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发表时间：
2016-12
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影响因子：
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通讯作者：
S. Oda;A. Tanimoto;Y. Ueda;M. Imanishi;Y. Terashima;C. Ricci
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文献类型：
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作者：
S. Oda;A. Tanimoto;Y. Ueda;M. Imanishi;Y. Terashima;C. Ricci
利用雨燕/爆发警报望远镜（BAT）、核光谱望远镜阵列（努斯塔）、朱雀望远镜、XMM-牛顿望远镜和钱德拉望远镜观测了超亮红外星系（ULIRG）UGC 5101在0.25-100 keV波段的宽带X射线谱。一个康普顿厚度的活动星系核（AGN）被密度为cm−2的氢柱遮蔽，在10 keV以上被探测到。用数字环面模型进行的光谱拟合有利于环面的大半开角°，表明严重遮蔽X射线源的材料的覆盖率是中等的。2-10 keV的本征光度被确定为erg s−1，这比之前仅使用10 keV以下的数据和简单的光谱模型估计的大了一倍。我们发现UGC 5101的[O iv] 26 μm谱线和2-10 keV光度之间的比值与正常的塞弗特星系相似，沿着的还有其他用努斯塔观测到的ULIRG，这表明相对于来自窄谱线区域的禁戒谱线通量，本地ULIRG的相当一部分并不是真正的“X射线微弱”。我们提出了一种可能的情况：（1）UGC 5101中的活动星系核不仅被赤道面附近的康普顿厚物质包围，而且还被环形洞区域的康普顿薄（cm-2）物质包围;（2）它以高爱丁顿速率吸积，具有陡峭的UV到X射线光谱能量分布。尽管如此，我们认为，在许多ULIRG活动星系核看起来并不特别（即，极X射线微弱），如最近的作品所建议的，与正常的塞弗茨相比。
We report the broadband X-ray spectra of the ultraluminous infrared galaxy (ULIRG) UGC 5101 in the 0.25–100 keV band observed with the Swift/Burst Alert Telescope (BAT), Nuclear Spectroscopic Telescope Array (NuSTAR), Suzaku, XMM-Newton, and Chandra. A Compton-thick active galactic nucleus (AGN) obscured with a hydrogen column density of cm−2 is detected above 10 keV. A spectral fit with a numerical torus model favors a large half-opening angle of the torus, °, suggesting that the covering fraction of material heavily obscuring the X-ray source is moderate. The intrinsic 2–10 keV luminosity is determined to be erg s−1, which is times larger than the previous estimate using only data below 10 keV with a simple spectral model. We find that UGC 5101 shows the ratio between the [O iv] 26 μm line and 2–10 keV luminosities similar to those of normal Seyfert galaxies, along with other ULIRGs observed with NuSTAR, indicating that a significant portion of local ULIRGs are not really “X-ray faint” with respect to the flux of forbidden lines originating from the narrow-line region. We propose a possible scenario that (1) the AGN in UGC 5101 is surrounded not only by Compton-thick matter located close to the equatorial plane but also by Compton-thin ( cm−2) matter in the torus-hole region and (2) it is accreting at a high Eddington rate with a steep UV to X-ray spectral energy distribution. Nevertheless, we argue that AGNs in many ULIRGs do not look extraordinary (i.e., extremely X-ray faint), as suggested by recent works, compared with normal Seyferts.