The vertical profiles of chain and spiral galaxies in the Hubble Space Telescope Ultra Deep Field (UDF) are fit to sech2 functions convolved with stellar profiles in order to measure the disk scale heights z0 in four passbands. The bulge regions of the spiral galaxies are avoided. Photometric redshifts give absolute scales. The rms heights of the giant clumps in these galaxies are also measured. The results indicate that UDF disks are thick, with an average z0 = 1.0 ± 0.4 kpc. The ratio of radial exponential scale length to z0 is ~3 ± 1.5. The scale heights are only 20% larger than the radii of the giant star-forming clumps and a factor of ~10 larger than the rms clump deviations around the midplanes. This suggests that the clumps formed from midplane gas and dissolved to make the thick disks. Redshifted stellar population models suggest ages of ~1 Gyr and mass column densities from 4 to 40 M☉ pc-2. The UDF disks look like young versions of modern thick disks. This resemblance is difficult to understand if galaxies grow over time or if subsequent accretion of thin disks gravitationally shrinks the observed thick disks. More likely, high-redshift disks are thick because their mass column densities are low; a velocity dispersion of only 14 km s-2 reproduces the observed thickness. Modern thick disks require more heating at high redshift. This is possible if the gas that eventually makes the thin disk is in place before the youngest age of a modern thick disk, and if the existing stars are heated during the delivery of this gas.
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机译：哈勃太空望远镜超深场（UDF）中的链星系和旋涡星系的垂直剖面适合于与恒星剖面卷积的sech2函数，以便在四个通带中测量盘刻度高度z0。避免了旋涡星系的凸起区域。光度红移给出绝对比例。还测量了这些星系中巨团的均方根高度。结果表明，UDF磁盘较厚，平均z0 = 1.0±0.4 kpc。径向指数标度长度与z0的比率为〜3±1.5。尺度高度仅比形成巨星的团块的半径大20％，比中平面周围的均方根团块偏差大约10倍。这表明团块由中平面气体形成并溶解形成厚盘。红移的恒星种群模型表明年龄约为1 Gyr，质谱柱密度为4至40M☉pc-2。 UDF磁盘看起来像现代厚磁盘的年轻版本。如果星系随时间增长，或者随后的细盘积聚在重力作用下使观察到的厚盘收缩，则很难理解这种相似性。高红移盘很可能很厚，因为它们的质量列密度很低。仅14 km s-2的速度色散再现了观察到的厚度。现代厚磁盘在高红移条件下需要更多热量。如果最终形成薄盘的气体在现代厚盘的最年轻年龄之前就位，并且在输送这种气体的过程中现有的恒星被加热，则这是可能的。
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