用哈勃空间望远镜NICMOS和ACS研究z~2亚毫米星系的形态
A Hubble Space Telescope NICMOS and ACS Morphological Study of z~2 Submillimetre Galaxies
摘要：
我们提出了一个定量的形态分析，使用HST NICMOS H160-和ACS I775波段成像的25光谱证实的亚毫米星系（SMG）的红移之间的z=0.7-3.4。我们的分析还采用了一个比较样本的更典型的恒星形成星系在类似的红移（如LBG），具有较低的远红外光度。这是第一次在近红外范围内以~0.1”分辨率（<1 kpc）对SMG形态进行大规模研究。我们发现SMG的半光半径（在I-和H-波段分别为2.3+/-0.3和2.8+/-0.4kpc）和不对称性与恒星形成星系的比较样本在统计上没有区别。然而，我们表明，SMG形态之间的休息帧UV和光学波段比典型的恒星形成的星系和解释这作为结构化尘埃遮蔽的证据。结果表明，复合观测到的SMG的H波段光分布与Sersic指数（n~2）拟合较好，说明SMG的恒星结构最好用球状/椭圆星系光分布来描述。我们还比较了SMG的大小和恒星质量的本地和高红移人口，并发现SMG的恒星密度是本地早型星系，以及发光，红色和致密的星系在z~1.5已被提出作为直接SMG的后代，虽然SMG恒星的质量和大小系统较大。总的来说，我们的研究结果表明，星系内发生的物理过程太复杂了，不能简单地以静止帧UV/光学形态为特征，这些形态似乎基本上与所有其他观测值（如热光度、恒星或动力学质量）解耦。
英文摘要：
We present a quantitative morphological analysis using HST NICMOS H160- and ACS I775- band imaging of 25 spectroscopically confirmed submillimetre galaxies (SMGs) which have redshifts between z=0.7-3.4. Our analysis also employs a comparison sample of more typical star-forming galaxies at similar redshifts (such as LBGs) which have lower far-infrared luminosities. This is the first large-scale study of the morphologies of SMGs in the near-infrared at ~0.1" resolution (<1kpc). We find that the half light radii of the SMGs (r_h=2.3+/-0.3 and 2.8+/-0.4kpc in the observed I- and H-bands respectively) and asymmetries are not statistically distinct from the comparison sample of star-forming galaxies. However, we demonstrate that the SMG morphologies differ more between the rest-frame UV and optical-bands than typical star-forming galaxies and interpret this as evidence for structured dust obscuration. We show that the composite observed H-band light profile of SMGs is better fit with a Sersic index with n~2, suggesting the stellar structure of SMGs is best described by a spheroid/elliptical galaxy light distribution. We also compare the sizes and stellar masses of SMGs to local and high-redshift populations, and find that the SMGs have stellar densities which are comparable to local early-type galaxies, as well as luminous, red and dense galaxies at z~1.5 which have been proposed as direct SMG descendants, although the SMG stellar masses and sizes are systematically larger. Overall, our results suggest that the physical processes occuring within the galaxies are too complex to be simply characterised by the rest-frame UV/optical morphologies which appear to be essentially decoupled from all other observables, such as bolometric luminosity, stellar or dynamical mass.
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