Broadband X-Ray Spectral Analysis of the Dual AGN System Mrk 739

We present the result of a broadband (0.5–70 keV) X-ray spectral analysis of the late-merger galaxy Mrk 739, which contains a dual active galactic nucleus (AGN), Mrk 739E and Mrk 739W, with a separation of ≈3.4 kpc. The spectra obtained with NuSTAR, Chandra, XMM-Newton, and Swift/BAT are simultaneously analyzed by separating the contributions from the two AGNs and extended emission with the Chandra data. To evaluate the reflection components from the AGN tori, we consider two models, a phenomenological one (pexrav and zgauss) and a more physically motivated one (XCLUMPY). On the basis of the results with XCLUMPY, we find that the AGNs in Mrk 739E and Mrk 739W have intrinsic 2–10 keV luminosities of 1.0 × 1043 and 7.5 × 1041 erg s−1 absorbed by hydrogen column densities of N H 1022cm−2 in Mrk 739E, CT(22)<0.50 at a 90% confidence limit, is found to be smaller than those found for late-merger ultra/luminous infrared galaxies, CT(22)=0.71±0.16 (mean and standard deviation). Considering the small star formation rate of Mrk 739E, we suggest that the gas-to-mass ratio of the host galaxy is an important parameter to determine the circumnuclear environment of an AGN in a late merger.

我们展示了对晚期合并星系Mrk 739进行的宽波段（0.5 - 70 keV）X射线光谱分析的结果，该星系包含一个双活动星系核（AGN），即Mrk 739E和Mrk 739W，它们之间的距离约为3.4 kpc。利用“核光谱望远镜阵列”（NuSTAR）、“钱德拉”（Chandra）、“XMM - 牛顿”（XMM - Newton）以及“雨燕”/“爆发警报望远镜”（Swift/BAT）所获取的光谱，通过利用钱德拉数据区分两个活动星系核以及扩展辐射的贡献进行了同时分析。为了评估来自活动星系核环面的反射成分，我们考虑了两种模型，一种是唯象模型（pexrav和zgauss），另一种是更具物理动机的模型（XCLUMPY）。基于XCLUMPY的结果，我们发现Mrk 739E和Mrk 739W中的活动星系核在2 - 10 keV的固有光度分别为1.0×10⁴³和7.5×10⁴¹ erg s⁻¹，Mrk 739E被氢柱密度为Nₕ = 10²² cm⁻²所吸收，在90%置信水平下，覆盖因子CT(22) < 0.50，发现其小于在晚期合并的极亮/亮红外星系中所发现的值，CT(22) = 0.71 ± 0.16（均值和标准差）。考虑到Mrk 739E较小的恒星形成率，我们认为宿主星系的气 - 质比是决定晚期合并中活动星系核核周环境的一个重要参数。