论文标题
星系中的中央分子区域：12CO与13CO的比率，碳预算和X因子
Central molecular zones in galaxies: 12CO-to-13CO ratios, carbon budget, and X factors
论文作者
论文摘要
本文在各种J转型中介绍了附近的126个星系中心的地面12CO和13CO测量。至少在四行中测量了60多个星系。前四个12CO转换的平均相对强度为1.00：0.92：0.70：0.57。前三个过境的平均12CO与13CO比为13.0、11.6和12.8。中央CO浓度的尺寸在地图中很好地定义，但通过多孔径光度法确定了很差。使用辐射转移模型（RADEX），我们得出了模型气体参数，其中假定的碳元素丰度和碳气体耗尽到灰尘是不确定性的主要原因。 The new CO data and published [CI] and [CII] data imply that CO, Co, and C+ each represent about one-third of the gas-phase carbon in the molecular interstellar medium in galaxy centers Their mean beam-averaged central molecular hydrogen column density is N(H2) = (1.5+/-0.2) x 10^(21) cm^(2) and CO-to-H2 conversion factors are typically ten times lower than `标准的银河系磁盘值，平均值x（co）=（1.9 +/- 0.2）x 10^（19）cm^（2）/k km/s。相应的[CI]至H2因子是X（CO）的五倍，X [CI] =（9 +/- 2）x 10^（19）cm^（2）/k km/s。对于[CII]，无法确定独特的转换因子。与星系磁盘中发现的高度相等的部分相比，相对于其CO强度的低分子气体中心相对于其CO强度的中心相对于其CO强度的中心大致相等的部分解释了。
This paper presents ground-based 12CO and 13CO measurements of 126 nearby galaxy centers in various J transitions. More than 60 galaxies were measured in at least four lines. The average relative intensities of the first four 12CO transitions are 1.00 : 0.92 : 0.70 : 0.57. The average 12CO-to-13CO ratios are 13.0, 11.6, and 12.8 for the first three transitiions. The sizes of central CO concentrations are well defined in maps, but poorly determined by multi-aperture photometry. Using radiative transfer models (RADEX), we derived model gas parameters, where the assumed carbon elemental abundances and carbon gas depletion onto dust are the main causes of uncertainty. The new CO data and published [CI] and [CII] data imply that CO, Co, and C+ each represent about one-third of the gas-phase carbon in the molecular interstellar medium in galaxy centers Their mean beam-averaged central molecular hydrogen column density is N(H2) = (1.5+/-0.2) x 10^(21) cm^(2) and CO-to-H2 conversion factors are typically ten times lower than the `standard' Milky Way disk value, with a mean X(CO) = (1.9+/-0.2) x 10^(19) cm^(2)/K km/s. The corresponding [CI]-to-H2 factor is five times higher than X(CO), with X[CI] = (9+/-2) x 10^(19) cm^(2)/K km/s. No unique conversion factor can be determined for [CII]. The low molecular gas content of galaxy centers relative to their CO intensities is explained in roughly equal parts by higher central gas-phase carbon abundances, elevated gas temperatures, and larger gas velocity dispersions than found in galaxy disks.
