A Multi-Transition Study of Molecules toward NGC 1068 based on High-Resolution Imaging Observations with ALMA
A Multi-Transition Study of Molecules toward NGC 1068 based on High-Resolution Imaging Observations with ALMA
复制标题
DOI：
10.1093/pasj/psu136
复制
发表时间：
2014-10
期刊：
影响因子：
--
通讯作者：
T. Nakajima;S. Takano;K. Kohno;N. Harada;E. Herbst;Y. Tamura;T. Izumi;A. Taniguchi;T. Tosaki
中科院分区：
文献类型：
--
作者：
T. Nakajima;S. Takano;K. Kohno;N. Harada;E. Herbst;Y. Tamura;T. Izumi;A. Taniguchi;T. Tosaki
我们展示了用阿塔卡马大型毫米/亚毫米阵列（ALMA）获得的0.8毫米波段分子图像和光谱，这些图像和光谱指向最近的一个具有活动星系核（AGN）的星系NGC 1068。观测到CO同位素在环核盘（CND）和星爆环部分的分布（$^{13}$CO和C$^{18}$O） $\it{J}$ = 3—2,CN $\it{N}$ = 3—2和CS $\it{J}$ = 7—6，角分辨率为$\sim$1)。$ ^{\ ' \ '} $ 3 $ \ * 1美元。$ ^{\ ' \ '}2美元。在局部热力学平衡的假设下，利用旋转图估计了这些分子以及在3-mm波段检测到的HNCO、CH$_{3}$CN、SO和CH$_{3}$OH等与冲击有关的分子的物理性质。CND中CO同位素和激波相关分子的旋转温度分别为14 ~ 22 K和20 ~ 40 K。虽然压缩带中CO同位素的柱密度仅为星爆环中的五分之一到三分之一，但在压缩带中与激波相关的分子的柱密度增加了3—10倍。我们还讨论了每个物种的化学性质，并将CND和星爆环中的分数丰度与银河系源（如冷核、热核和激波分子云）的分数丰度进行了比较，以研究其总体特征。我们发现激波相关分子的丰度与热核和/或激波云的丰度比与冷核的丰度更相似。CND拥有相对复杂的分子，这些分子通常与激波分子云或热核有关。由于高x射线通量可以解离这些分子，因此它们也必须驻留在屏蔽x射线的区域。
We present 0.8-mm band molecular images and spectra obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) toward one of the nearest galaxies with an active galactic nucleus (AGN), NGC 1068. Distributions of CO isotopic species ($^{13}$CO and C$^{18}$O) $\it{J}$ = 3--2, CN $\it{N}$ = 3--2 and CS $\it{J}$ = 7--6 are observed toward the circumnuclear disk (CND) and a part of the starburst ring with an angular resolution of $\sim$1.$^{\prime\prime}$3 $\times$ 1.$^{\prime\prime}$2. The physical properties of these molecules and shock-related molecules such as HNCO, CH$_{3}$CN, SO, and CH$_{3}$OH detected in the 3-mm band were estimated using rotation diagrams under the assumption of local thermodynamic equilibrium. The rotational temperatures of the CO isotopic species and the shock-related molecules in the CND are, respectively, 14--22 K and upper limits of 20--40 K. Although the column densities of the CO isotopic species in the CND are only from one-fifth to one-third of that in the starburst ring, those of the shock-related molecules are enhanced by a factor of 3--10 in the CND. We also discuss the chemistry of each species, and compare the fractional abundances in the CND and starburst ring with those of Galactic sources such as cold cores, hot cores, and shocked molecular clouds in order to study the overall characteristics. We find that the abundances of shock-related molecules are more similar to abundances in hot cores and/or shocked clouds than to cold cores. The CND hosts relatively complex molecules, which are often associated with shocked molecular clouds or hot cores. Because a high X-ray flux can dissociate these molecules, they must also reside in regions shielded from X-rays.