NGC 1097中心分子气体的物理条件
Physical Condition of Molecular Gas at the Centre of NGC 1097
摘要：
我们利用Xco转换因子、局域热平衡和大速度梯度近似，从NGC 1097中心21”（kpc）CO的五个不同的低跃迁，参数化了星际介质的冷相和暖相。我们应用单组分模型，导出了典型的动力学温度~ 33 K，以及它的分子氢密度和CO柱密度。一个双组分模型的结果在85%的冷总气体分数与90 K温暖的对应。此外，我们“解决”的空间未解决的单碟观测通过选择在干涉速度图对应于特定区域的速度通道。我们已经选择了五个这样的区域，并发现在这些地区的物理性质是可比的，从全线配置文件。这意味着NGC 1097的中心kpc在本质上是相当均匀的，尽管这些区域在环内并不是唯一的，但沿着环的恒星形成是均匀分布的（与最近的赫歇尔观测一致）。我们进一步修正了这个LINER/Sy 1星系原型中超大质量黑洞的质量流入率，并发现，考虑到总的星际介质，并仔细应用盘厚度和相应的稳定性标准的贡献，以前的估计增加了10倍。最后，我们利用对表面密度与CO排放的独立估算，计算了NGC 1097中心的Xco，得到半径为10.5“时Xco=（2.8+-0.5 x10 ^20 cm^-2（K km s^-1）^-1，半径为7.5”时Xco=（5.0+-0.5 x10 ^20 cm^-2（K km s^-1）^-1。与所描述的方法和分析，我们已经证明，重要的物理特性可以推导出一个决议超越单碟分辨率元素，但是，谨慎是必要的解释结果。（删节）
英文摘要：
We have used the Xco conversion factor, Local Thermal Equilibrium and Large Velocity Gradient approximation to parametrize the cold and warm phase of the interstellar medium from five different low transitions of CO in the central 21"(kpc) of NGC 1097. We have applied a one-component model and derived a typical kinetic temperature of ~33K, and its molecular Hydrogen density and a CO column density. A two-component model results in 85% cold-to-total gas fraction with a 90K warm counterpart. Furthermore, we "resolve" the spatially unresolved single dish observations by selecting velocity channels that in an interferometric velocity map correspond to specific regions. We have selected five such regions and found that the physical properties in these regions are comparable to those derived from the full line profile. This implies that the central kpc of NGC 1097 is rather homogeneous in nature, and, although the regions are not uniquely located within the ring, the star formation along the ring is homogeneously distributed (in agreement with recent Herschel observations). We have further revised the mass inflow rate onto the Supermassive Black Hole in this prototype LINER/Sy1 galaxy and found that, accounting for the total interstellar medium and applying a careful contribution of the disc thickness and corresponding stability criterion, increases the previous estimations by a factor 10. Finally we have calculated the Xco for the centre of NGC 1097 using an independent estimation of the surface density to the CO emission, and obtained Xco=(2.8+-0.5)x10^20 cm^-2(K km s^-1)^-1 at radius 10.5" and Xco=(5.0+-0.5)x10^20 cm^-2(K km s^-1)^-1 at 7.5". With the approach and analysis described, we have demonstrated that important physical properties can be derived to a resolution beyond the single dish resolution element, however, caution is necessary for interpreting the results.(Abriged)
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