标题： 用宽波段X射线光谱研究超亮红外星系UGC 5101中的康普顿厚活动星系核 显示英文标题

标题： Shedding Light on the Compton-thick Active Galactic Nucleus in the Ultra-luminous Infrared Galaxy UGC 5101 with Broadband X-ray Spectroscopy

摘要： 我们报告了通过Swift/Burst Alert Telescope (BAT)、NuSTAR、Suzaku、XMM-Newton和Chandra在0.25-100 keV波段观测到的超亮红外星系(ULIRG) UGC 5101的宽频X射线谱。在10 keV以上检测到一个被氢柱密度为$\approx 1.3\times10^{24}$cm$^{-2}$的厚康普顿AGN。用数值环面模型进行光谱拟合，支持环面较大的半开角$>41$度，表明严重遮挡X射线源的物质覆盖分数是中等的。固有2-10 keV光度确定为$\approx 1.4\times 10^{43}$erg s$^{-1}$，这比仅使用低于10 keV的数据并采用简单光谱模型之前的估计值大$\approx$2.5倍。我们发现UGC 5101的[O IV] 26$\mu$m线与2-10 keV光度的比率与其他正常塞弗特星系以及用NuSTAR观测的其他ULIRGs相似，表明本地ULIRGs的相当一部分实际上并不是相对于来自窄线区(NLR)的禁线通量而言的“X射线暗弱”。 我们提出一种可能的场景，(1) UGC 5101 中的活动星系核不仅被位于赤道平面附近的康普顿厚物质包围，而且还被托勒斯孔区域中的康普顿薄（$N_\mathrm{H} \sim 10^{21}$cm$^{-2}$）物质包围，以及 (2) 它以高爱丁顿率吸积，并具有陡峭的紫外至X射线光谱能量分布。 然而，我们认为与正常塞弗特星系相比，许多ULIRGs中的活动星系核并不显得特别（即，极端X射线暗淡），正如最近的研究所建议的那样。 显示英文摘要

摘要： We report the broadband X-ray spectra of the ultra-luminous infrared galaxy (ULIRG) UGC 5101 in the 0.25-100 keV band observed with Swift/Burst Alert Telescope (BAT), NuSTAR, Suzaku, XMM-Newton, and Chandra. A Compton-thick AGN obscured with a hydrogen column density of $\approx 1.3\times10^{24}$ cm$^{-2}$ is detected above 10 keV. A spectral fit with a numerical torus model favors a large half opening angle of the torus, $>41$ degrees, 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 $\approx 1.4\times 10^{43}$ erg s$^{-1}$, which is $\approx$2.5 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 $\mu$m 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 (NLR). 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 ($N_\mathrm{H} \sim 10^{21}$ 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.