A Massive Molecular Torus inside a Gas-poor Circumnuclear Disk in the Radio Galaxy NGC 1052 Discovered with ALMA
A Massive Molecular Torus inside a Gas-poor Circumnuclear Disk in the Radio Galaxy NGC 1052 Discovered with ALMA
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DOI：
10.3847/1538-4357/ab8bd6
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发表时间：
2020-04
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影响因子：
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通讯作者：
S. Kameno;S. Sawada-Satoh;C. Impellizzeri;D. Espada;N. Nakai;H. Sugai;Y. Terashima;K. Kohno;Minju M. Lee;Sergio Mart'in
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作者：
S. Kameno;S. Sawada-Satoh;C. Impellizzeri;D. Espada;N. Nakai;H. Sugai;Y. Terashima;K. Kohno;Minju M. Lee;Sergio Mart'in
我们报告 ALMA 对 NGC 1052 的观测，以寻找贫气活跃星系核中的质量吸积。我们检测到的 CO 排放代表了一个旋转的环状核周盘 (CND)，其气体质量为 5.3 × 105 M⊙。 CND 的气体质量比典型的具有核周恒星形成的塞弗特星系的气体质量要小，并且气体含量太少，无法将质量吸积到中央引擎上。连续发射铸造了 CO、HCN、HCO+、SO、SO2、CS、CN 和 H2O 的分子吸收特征，其中包括 H13CN 和 HC15N 以及振动激发 (v2 = 1) HCN 和 HCO+。比 CND 发射线宽度更宽的吸收线宽度意味着存在半径为 2.4 ± 1.3 pc 且厚度比为 0.7 ± 0.3 的几何厚分子环面。我们利用H12CN、H13CN和HCO+吸收特征，并采用12C与13C以及HCO+与H2的丰度比，获得了(3.3±0.7)×1025cm−2的H2柱密度，并推导出了(1.3±0.3)×107M⊙的环面气体质量，约为中心黑洞质量的9%。环面中的分子气体是块状的，估计覆盖因子为 。推断环内团块的气体密度为(6.4±1.3)×107cm−3，满足H2O脉塞的激发条件。环面中的比角动量超过了从 CND 推断出的平坦旋转曲线，表明在 14.4 pc 影响范围内存在开普勒旋转。
We report ALMA observations of NGC 1052 to search for mass accretion in a gas-poor active galactic nucleus. We detected CO emission representing a rotating ring-like circumnuclear disk (CND) seen edge-on with a gas mass of 5.3 × 105 M⊙. The CND has smaller gas mass than that in typical Seyfert galaxies with circumnuclear star formation and is too gas-poor to drive mass accretion onto the central engine. The continuum emission casts molecular absorption features of CO, HCN, HCO+, SO, SO2, CS, CN, and H2O, with H13CN and HC15N and vibrationally excited (v2 = 1) HCN and HCO+. Broader absorption line widths than CND emission-line widths imply the presence of a geometrically thick molecular torus with a radius of 2.4 ± 1.3 pc and a thickness ratio of 0.7 ± 0.3. We obtain an H2 column density of (3.3 ± 0.7) × 1025 cm−2 using H12CN, H13CN, and HCO+ absorption features and adopting abundance ratios of 12C to 13C and HCO+ to H2, and we derived a torus gas mass of (1.3 ± 0.3) × 107 M⊙, which is ∼9% of the central black hole mass. The molecular gas in the torus is clumpy, with an estimated covering factor of . The gas density of the clumps inside the torus is inferred to be (6.4 ± 1.3) × 107 cm−3, which meets the excitation conditions for an H2O maser. The specific angular momentum in the torus exceeds the flat rotation curve extrapolated from that of the CND, indicating a Keplerian rotation inside a 14.4 pc sphere of influence.