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首页> 外文期刊>PASJ: Publications of the Astronomical Society of Japan >A statistical study of giant molecular clouds traced by (CO)-C-13, (CO)-O-18, CS, and CH3OH in the disk of NGC 1068 based on ALMA observations
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A statistical study of giant molecular clouds traced by (CO)-C-13, (CO)-O-18, CS, and CH3OH in the disk of NGC 1068 based on ALMA observations

机译：基于ALMA观测的NGC 1068盘中的（CO）-C-13，（CO）-13，（CO）-118，CS和CH3OH的巨型分子云的统计研究

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We present 1.'' 4 (98 pc) resolution ALMA observations of (CO)-C-13(J = 1-0), (CO)-O-18(J = 1-0), CS(J = 2-1), and CH3OH(J(K) = 2(K)-1(K)) molecular rotational lines in the central 1' (4.2 kpc) diameter region of NGC 1068 to study the physical and chemical properties of giant molecular clouds (GMCs) and to test whether these GMC-scale properties are linked to the larger-scale galactic environment. Using the derived (CO)-C-13 cube, we have identified 187 high-significance (> 8 sigma) GMCs by employing the CLUMPFIND algorithm. The molecular gas masses of GMCs (M-13CO), derived from the (CO)-C-13 data, range from 1.8 x 10(4) M-circle dot to 4.2 x 10(7) M-circle dot. A mass function of GMCs in NGC 1068 has been obtained for the first time at similar to 100 pc resolution. We find the slope of the mass function gamma = -1.25 +/- 0.07 for a mass range of M-13CO >= 10(5) M-circle dot. This is shallower than the GMCs in the disk regions of the Milky Way, M 51, and NGC 300. Further, we find that the highmass cut-off of the GMC mass function occurs at M-13CO similar to 6 x 10(7) M-circle dot, which is an order of magnitude larger than that in the nuclear bar region of M 51, indicating that the more massive clouds dominate the mass budget in NGC 1068. The observed (CO)-O-18(J = 1-0)/(CO)-C-13(J = 1-0) intensity ratios are found to be fairly uniform (0.27 +/- 0.05) among the identified GMCs. In contrast, the CH3OH(J(K) = 2(K)-1(K))/(CO)-C-13(J = 1-0) ratios exhibit striking spatial variation across the disk, with the smallest values around the bar-end (< 0.03), and larger ratios along the spiral arms (similar to 0.1-0.2). We find that GMCs with detectable methanol emission tend to have systematically larger velocity widths than those without methanol emission, suggesting that (relatively weak) shocks are responsible for the enhancement of the CH3OH/(CO)-C-13 ratios of GMCs in the disk of NGC 1068.
机译：我们现在有1个NGC1068中心1’（4.2 kpc）直径区域（CO）-C-13（J=1-0），（CO）-O-18（J=1-0），CS（J=2-1）和CH3OH（J（K）=2（K）-1（K））分子旋转线的4（98 pc）分辨率ALMA观测，以研究巨分子云（GMC）的物理和化学性质，并测试这些GMC尺度的性质是否与更大尺度的银河系环境有关。使用导出的（CO）-C-13立方体，我们通过使用CLUMPFIND算法识别了187个高显著性（>8西格玛）GMC。根据（CO）-C-13数据得出的GMC（M-13CO）的分子气体质量范围为1.8 x 10（4）M圆点到4.2 x 10（7）M圆点。首次获得了NGC1068中GMC的质量函数，其分辨率接近100PC。我们发现质量函数γ的斜率为-1.25+/-0.07，质量范围为M-13CO>=10（5）M圆点。这比银河系、M51和NGC300盘区的GMC浅。此外，我们发现，GMC质量函数的高质量截止发生在M-13CO，类似于6 x 10（7）M圆点，这比M 51核棒区域大一个数量级，表明更大质量的云主导NGC 1068的质量预算。在已识别的GMC中，观察到的（CO）-O-18（J=1-0）/（CO）-C-13（J=1-0）强度比相当均匀（0.27+/-0.05）。相比之下，CH3OH（J（K）=2（K）-1（K））/（CO）-C-13（J=1-0）比值在整个圆盘上表现出显著的空间变化，棒端周围的值最小（<0.03），螺旋臂上的比值更大（类似于0.1-0.2）。我们发现，与没有甲醇排放的GMC相比，具有可检测甲醇排放的GMC往往具有更大的系统速度宽度，这表明（相对较弱的）冲击是NGC 1068盘中GMC的CH3OH/（CO）-C-13比率增强的原因。

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