COALAS：I. z=2.16时蛛网原星系团的ATCA CO（1-0）巡天和光度函数
COALAS: I. ATCA CO(1-0) survey and luminosity function in the Spiderweb protocluster at z=2.16
摘要：
我们报告一个详细的CO（1-0）调查的星系原星团领域在$z=2.16$，基于475小时的观测与澳大利亚望远镜紧凑阵列。我们构建了一个由13个独立点组成的大型镶嵌图，覆盖了21弧分的$^2$和$\pm6500$ km/s速度范围。我们获得了一个强大的样本46 CO（1-0）检测跨越$z=2.09-2.22$，构成最大的样品分子气体测量的原星系团。CO发射体在$z=2.12-2.21$处显示出高密度，这表明一个星系超原星系团或一个与~120 cMpc大小的大尺度细丝相连的原星系团。我们发现，90%的CO发射器有距离$>0'.5-4'$的中心星系，表明小面积的调查将错过大多数的天然气水库在类似的结构。一半的CO发射体的速度大于逃逸速度，这似乎是重力束缚的集群核心。这些未结合的源在中心周围的$R_{200}$半径内几乎找不到，这与星系团核心坍缩而外部区域仍在形成的图像一致。与其他原星团相比，该结构包含相对较多的CO发射体，具有相对较窄的线宽和较高的光度，表明星系合并。我们使用这些CO发射器放置在过密环境中的CO光度函数和分子气体密度的第一个约束。CO光度函数的振幅为1.6 $\pm$ 0.5个数量级高于观测到的场星系样本在$z\sim2$，和一个数量级高于半分析SHARK模型的星系原星团的预测。我们推导出一个高分子气体密度的$0.6-1.3\times10^{9}$ $M_\odot$ cMpc $^{-3}$的这种结构，符合预测的冷气密度的大规模结构从流体动力学DIANOGA模拟。
英文摘要：
We report a detailed CO(1-0) survey of a galaxy protocluster field at $z=2.16$, based on 475 hours of observations with the Australia Telescope Compact Array. We constructed a large mosaic of 13 individual pointings, covering an area of 21 arcmin$^2$ and $\pm6500$ km/s range in velocity. We obtain a robust sample of 46 CO(1-0) detections spanning $z=2.09-2.22$, constituting the largest sample of molecular gas measurements in protoclusters to date. The CO emitters show an overdensity at $z=2.12-2.21$, suggesting a galaxy super-protocluster or a protocluster connected to large-scale filaments with ~120 cMpc size. We find that 90% CO emitters have distances $>0'.5-4'$ to the center galaxy, indicating that small area surveys would miss the majority of gas reservoirs in similar structures. Half of the CO emitters have velocities larger than escape velocities, which appears gravitationally unbound to the cluster core. These unbound sources are barely found within the $R_{200}$ radius around the center, which is consistent with a picture in which the cluster core is collapsed while outer regions are still in formation. Compared to other protoclusters, this structure contains relatively more CO emitters with relatively narrow line width and high luminosity, indicating galaxy mergers. We use these CO emitters to place the first constraint on the CO luminosity function and molecular gas density in an overdense environment. The amplitude of the CO luminosity function is 1.6$\pm$0.5 orders of magnitudes higher than observed for field galaxy samples at $z\sim2$, and one order of magnitude higher than predictions for galaxy protoclusters from semi-analytical SHARK models. We derive a high molecular gas density of $0.6-1.3\times10^{9}$ $M_\odot$ cMpc$^{-3}$ for this structure, consistent with predictions for cold gas density of massive structures from hydro-dynamical DIANOGA simulations.
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