LSB星系Malin~2盘中扩展分子气体的探测
Detection of Extended Molecular Gas in the Disk of the LSB Galaxy Malin~2
摘要：
我们的目标是看看是否有分子气体延伸到整个星系Malin 2的光学低表面亮度盘。我们用安装在IRAM 30米望远镜上的外差接收器阵列（HERA），在马林~2的9个不同位置上进行了CO（2- 1）线频率的深度观测。在11 km/s的速度分辨率下，总观测时间为11小时，我们实现了~1 mK的灵敏度水平。我们在Malin~2中探测到CO（2-1）谱线发射。在9个HERA光束中的4个中检测到该线;第5个光束显示边缘检测。这些结果不仅证实了马林2星系盘中存在分子气体，而且还表明分子气体分布在星系盘观测采样的34 kpc半径范围内。圆盘中的平均分子气体表面密度为$1.1\pm0.2~M_{\odot}~pc^{-2}$，分子气体质量介于极限$4.9\times10^{8}$和$8.3\times10^{8}~M_{\odot}$之间。观测到的分子气体的速度色散（$\sim 13$ \，km\，s $^{-1}$）比恒星形成星系盘中的高。这可以解释磁盘的稳定性和低恒星形成活动。
英文摘要：
Our goal is to see if there is molecular gas extending throughout the optical low surface brightness disk of the galaxy Malin 2. We used the heterodyne receiver array (HERA) mounted on the IRAM 30m telecope to make deep observations at the frequency of the CO(2--1) line at nine different positions of Malin~2. With a total observing time of 11 hours at a velocity resolution of 11 km/s we achieve a sensitivity level of ~1 mK. We detect CO(2-1) line emission from Malin~2. The line is detected in four of the nine HERA beams; a fifth beam shows a marginal detection. These results not only confirm that there is molecular gas in the disk of Malin 2, but they also show that it is spread throughout the inner 34~kpc radius as sampled by the observations of the galaxy disk. The mean molecular gas surface density in the disk is $1.1\pm0.2~M_{\odot}~pc^{-2}$ and the molecular gas mass lies between the limits $4.9\times10^{8}$ to $8.3\times10^{8}~M_{\odot}$. The observed velocity dispersion of the molecular gas is higher ($\sim 13$\,km\,s$^{-1}$) than in star forming galactic disks. This could explain the disk stability and its low star formation activity.
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