英仙座星系团X射线冷却流沉积的NGC 1275中径向流入的分子气体
Radially-Inflowing Molecular Gas in NGC 1275 Deposited by a X-ray Cooling Flow in the Perseus Cluster
摘要：
我们对英仙座星系团中心的cD星系NGC 1275（英仙座A）的分子气体进行了CO（2-1）成像，空间分辨率为$\sim$ 1 kpc，中心区域半径为$\sim$ 10 kpc。每A已知含有$\sim$ 1.3x10 $^{10}$ M $_\odot$的分子气体，已被提出从合并或气体丰富的星系的冲压压力剥离捕获，或从X射线冷却流吸积。在我们的图像中检测到的分子气体的总质量为$\sim$ 4x 10 $^9$ M $_\odot$，并且第一次可以看到集中在三个径向细丝中，长度从至少1.1-2.4 kpc，所有这些细丝都位于横跨星系中心的东西方向，半径为$\sim$ 8 kpc。东部和外部的西灯丝表现出更大的蓝移速度与半径减小，而内部的西灯丝跨越星系的系统速度。分子气体没有显示出轨道运动的特征，因此不太可能是从富含气体的星系中捕获的。相反，我们能够再现观察到的两个外部细丝的运动学作为自由落体的引力势的每A，如果他们起源于X射线冷却流将是预期的。事实上，所有三个灯丝都位于Per A射电喷流雕刻出的两个突出的X射线腔之间，并且非常类似于星系团核心中最冷的X射线气体的空间分布。仅在最外层的两个细丝中，推断的质量沉积速率大约为75 M $_odot$/年$^{-1}$。这种冷却流可以提供几乎连续的分子气体供应，为Per A中的活性核提供燃料。
英文摘要：
We have imaged in CO(2-1) the molecular gas in NGC 1275 (Perseus A), the cD galaxy at the center of the Perseus Cluster, at a spatial resolution of $\sim$1 kpc over a central region of radius $\sim$ 10 kpc. Per A is known to contain $\sim$1.3x10$^{10}$ M$_\odot$ of molecular gas, which has been proposed to be captured from mergers with or ram-pressure stripping of gas-rich galaxies, or accreted from a X-ray cooling flow. The molecular gas detected in our image has a total mass of $\sim$4x10$^9$ M$_\odot$, and for the first time can be seen to be concentrated in three radial filaments with lengths ranging from at least 1.1-2.4 kpc all lying in the east-west directions spanning the center of the galaxy to radii of $\sim$8 kpc. The eastern and outer western filaments exhibit larger blueshifted velocities with decreasing radii, whereas the inner western filament spans the systemic velocity of the galaxy. The molecular gas shows no signature of orbital motion, and is therefore unlikely to have been captured from gas-rich galaxies. Instead, we are able to reproduce the observed kinematics of the two outer filaments as free-fall in the gravitational potential of Per A, as would be expected if they originate from a X-ray cooling flow. Indeed, all three filaments lie between two prominent X-ray cavities carved out by radio jets from Per A, and closely resembles the spatial distribution of the coolest X-ray gas in the cluster core. The inferred mass-deposition rate into the two outermost filaments alone is roughly 75 M$_odot$ yr$^{-1}$. This cooling flow can provide a nearly continuous supply of molecular gas to fuel the active nucleus in Per A.
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