arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1607.08253astro-ph.GA
收藏

Milky Way型星系中的CO暗气体和分子细丝-- II:气体的温度分布

CO-dark gas and molecular filaments in Milky Way-type galaxies - II: The temperature distribution of the gas

Simon C. O. Glover, Rowan J. Smith

摘要:

利用AREPO动网格程序模拟了一系列盘星系中CO暗分子氢(H2)的温度分布。在类似于银河系的条件下,我们发现H2在10 - 100 K范围内具有平坦的温度分布。在$T < 30$ K下,气体几乎完全是分子的,并且具有高的CO含量,而在$T > 30$ K下,H2分数跨越更宽的范围,并且CO含量小,允许我们将这两个区域中的气体分别分类为CO-亮和CO-暗。CO暗H2中的平均声速为0.64 km/s,显著低于冷原子气体中的值(1.15 km/s),这意味着CO暗分子相比其原子相更容易受到湍流压缩和引力坍缩的影响。我们进一步表明,CO暗H2的温度是非常敏感的星际辐射场的强度,但在CO亮H2的条件基本保持不变。最后,我们研究的有用性的[CII]和[OI]精细结构线作为示踪剂的CO-暗气体。我们表明,在银河系一样的条件下,从这种气体扩散[CII]发射应该是可检测的。然而,它是这种气体的有问题的示踪剂,因为在发射的亮度和H2表面密度之间仅存在弱相关性。[OI]线的情况甚至更糟,它与H2表面密度没有相关性。

英文摘要:

We investigate the temperature distribution of CO-dark molecular hydrogen (H2) in a series of disk galaxies simulated using the AREPO moving-mesh code. In conditions similar to those in the Milky Way, we find that H2 has a flat temperature distribution ranging from 10 - 100 K. At $T < 30$ K the gas is almost fully molecular and has a high CO content, whereas at $T > 30$ K, the H2 fraction spans a broader range and the CO content is small, allowing us to classify gas in these two regimes as CO-bright and CO-dark, respectively. The mean sound speed in the CO-dark H2 is 0.64 km/s, significantly lower than the value in the cold atomic gas (1.15 km/s), implying that the CO-dark molecular phase is more susceptible to turbulent compression and gravitational collapse than its atomic counterpart. We further show that the temperature of the CO-dark H2 is highly sensitive to the strength of the interstellar radiation field, but that conditions in the CO-bright H2 remain largely unchanged. Finally, we examine the usefulness of the [CII] and [OI] fine structure lines as tracers of the CO-dark gas. We show that in Milky Way-like conditions, diffuse [CII] emission from this gas should be detectable. However, it is a problematic tracer of this gas, as there is only a weak correlation between the brightness of the emission and the H2 surface density. The situation is even worse for the [OI] line, which shows no correlation with the H2 surface density.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑