z~0.6的星团星系：运动学，稳定性和与其它红移类似星系的比较
Clumpy galaxies at z~0.6: kinematics, stability, and comparison with analogs at other redshifts
摘要：
最近对z~2星系的空间分辨运动学观测表明，远距离星团星系是Jeans不稳定盘，是形成本星系的重要通道。我研究了z~0.6的cluerian星系的运动学，并将它们的性质与高红移和低红移的相应星系进行了比较。我从具有代表性的中等质量发射线星系I中选取了11个z~0.6的星团星系。选择是基于HST/ACS图像的静止帧UV形态学，模仿通常在较高红移下使用的选择标准。它们的空间分辨运动学推导出的框架内的INUS调查，使用VLT/FLAMES-GIRAFFE多积分场摄谱仪。对于那些表现出大尺度旋转的，我推导出了Toomre Q参数，它表征了它们的气相和恒星相的稳定性。我发现，在z~0.6的紫外选择的cluerian星系的分数是20+/-12%。其中大约一半（45+/-30%）具有与Jeans不稳定盘不一致的复杂运动学，而其余一半（55+/-30%）则显示出大规模的旋转。后者揭示了一个稳定的气相，但它们的恒星相的贡献，使它们在全球范围内不稳定的团块形成。星团星系在z~0.6处的不稳定性似乎比z~2处要小，这可以解释为什么在z~0.6星团星系的静止坐标系光学图像中，紫外团簇往往会消失，而z~2星团星系则相反，在z~2星团星系中，恒星相位会大幅碎裂。这表明前者对应于叠加在更平滑的质量分布上的斑片状恒星形成区。一个可能的和广泛的驱动团块形成的场景依赖于冷流穿透星云星系居住的暗物质晕的不稳定性。虽然这样的气体吸积过程被预测在大质量的z~2晕中是重要的，但它也被预测在类似的z~0.6晕中被强烈抑制，这可以解释为什么最低z的星系似乎是由不同的机制驱动的。相反，我发现相互作用可能是导致z 1的clueros星系形成的主要驱动力<1. I argue that the nature of z>，clueros星系仍然更加不确定。虽然冷流可能是z~2的重要驱动力，但我也认为，在z=2和z=3之间观察到的和累积的合并分数足够大，因此每个z~2星系可能是在过去1 Gyr内发生合并的结果。我的结论是，这是过早地排除合并作为一个普遍的驱动力星系演化从z~2到z=0。
英文摘要：
Distant clumpy galaxies are thought to be Jeans-unstable disks, and an important channel for the formation of local galaxies, as suggested by recent spatially-resolved kinematic observations of z~2 galaxies. I study the kinematics of clumpy galaxies at z~0.6, and compare their properties with those of counterparts at higher and lower redshifts. I selected a sample of 11 clumpy galaxies at z~0.6 from the representative sample of emission line, intermediate-mass galaxies IMAGES. Selection was based on rest-frame UV morphology from HST/ACS images, mimicking the selection criteria commonly used at higher redshifts. Their spatially-resolved kinematics were derived in the frame of the IMAGES survey, using the VLT/FLAMES-GIRAFFE multi-integral field spectrograph. For those showing large-scale rotation, I derived the Toomre Q parameter, which characterizes the stability of their gaseous and stellar phases. I find that the fraction of UV-selected clumpy galaxies at z~0.6 is 20+/-12%. Roughly half of them (45+/-30%) have complex kinematics inconsistent with Jeans-unstable disks, while those in the remaining half (55+/-30%) show large-scale rotations. The latter reveal a stable gaseous phase, but the contribution of their stellar phase makes them globally unstable to clump formation. Clumpy galaxies appear to be less unstable at z~0.6 than at z~2, which could explain why the UV clumps tend to vanish in rest-frame optical images of z~0.6 clumpy galaxies, conversely to z~2 clumpy galaxies, in which the stellar phase can substantially fragment. This suggests that the former correspond to patchy star-formation regions superimposed on a smoother mass distribution. A possible and widespread scenario for driving clump formation relies on instabilities by cold streams penetrating the dark matter halos where clumpy galaxies inhabit. While such a gas accretion process is predicted to be significant in massive, z~2 haloes, it is also predicted to be strongly suppressed in similar, z~0.6 haloes, which could explain why lowest-z clumpy galaxies appear to be driven by a different mechanism. Instead, I found that interactions are probably the dominant driver leading to the formation of clumpy galaxies at z<1. I argue that the nature of z>1 clumpy galaxies remains more uncertain. While cold flows could be an important driver at z~2, I also argue that the observed and cumulative merger fraction between z=2 and z=3 is large enough so that every z~2 galaxy might be the result of a merger that occurred within their past 1 Gyr. I conclude that it is premature to rule out mergers as a universal driver for galaxy evolution from z~2 down to z=0.
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