Nature of Compton-thick Active Galactic Nuclei in “Nonmerging” Luminous Infrared Galaxies UGC 2608 and NGC 5135 Revealed with Broadband X-Ray Spectroscopy
Nature of Compton-thick Active Galactic Nuclei in “Nonmerging” Luminous Infrared Galaxies UGC 2608 and NGC 5135 Revealed with Broadband X-Ray Spectroscopy
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DOI：
10.3847/1538-4357/ab94b1
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
S. Yamada;Y. Ueda;A. Tanimoto;S. Oda;M. Imanishi;Y. Toba;C. Ricci
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文献类型：
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作者：
S. Yamada;Y. Ueda;A. Tanimoto;S. Oda;M. Imanishi;Y. Toba;C. Ricci
我们利用核光谱望远镜阵列、朱雀、XMM-牛顿和钱德拉的数据，分析了两个“非合并”发光红外星系（LIRG）UGC 2608和NGC 5135中活动星系核（AGN）的宽带X射线光谱。应用X射线块环面模型（XCLUMPY），我们发现两个源具有相似的光谱，其特征是康普顿厚（CT）吸收（∼ 5–7 × 1024 cm−2）和小环面角宽度（σ < 20°）。固有的 2-10 keV 光度为 × 1043 erg s−1 (UGC 2608) 和 × 1043 erg s−1 (NGC 5135)。 [O iv] 与核 12 μm 的光度比大于典型 Seyferts 的光度比，这与通过 X 射线光谱从环面角宽度和柱密度估计的环面覆盖因子 (0.7) 一致。环面覆盖因子和 Eddington 比率 (∼ 0.1) 遵循 Ricci 等人发现的关系。对于局部活动星系核，这意味着它们的环面在几何上变得很薄，因为活动星系核的巨大辐射压力吹出了环面的某些部分。这些结果表明，这些“非合并”LIRG 中的 CT AGN 只是通过大视线柱密度边缘看到的正常 AGN 群体。它们与后期合并中的埋藏 CT AGN 形成鲜明对比，后者即使在较大的爱丁顿比率下也具有较大的环面覆盖因子。
We have analyzed the broadband X-ray spectra of active galactic nuclei (AGNs) in two “nonmerging” luminous infrared galaxies (LIRGs), UGC 2608 and NGC 5135, utilizing the data of Nuclear Spectroscopic Telescope Array, Suzaku, XMM-Newton, and Chandra. Applying the X-ray clumpy-torus model (XCLUMPY), we find that both sources have similar spectra characterized by Compton-thick (CT) absorption ( ∼ 5–7 × 1024 cm−2) and small torus angular width (σ < 20°). The intrinsic 2–10 keV luminosities are × 1043 erg s−1 (UGC 2608) and × 1043 erg s−1 (NGC 5135). The [O iv]-to-nuclear-12 μm luminosity ratios are larger than those of typical Seyferts, which are consistent with the torus covering factors ( 0.7) estimated from the torus angular widths and column densities by X-ray spectroscopy. The torus covering factors and Eddington ratios ( ∼ 0.1) follow the relation found by Ricci et al. for local AGNs, implying that their tori become geometrically thin, due to significant radiation pressure of the AGN that blows out some part of the tori. These results indicate that the CT AGNs in these “nonmerger” LIRGs are just a normal AGN population seen edge-on through a large line-of-sight column density. They are in contrast to the buried CT AGNs in late-stage mergers that have large torus covering factors even at large Eddington ratios.