HUDF/XDF、HUDF09、ERS、CANDELS-South和CANDELS-North场>4000 z~4-8伽辽金的紫外连续斜率
UV-Continuum Slopes of >4000 z~4-8 Galaxies from the HUDF/XDF, HUDF09, ERS, CANDELS-South, and CANDELS-North Fields
摘要：
我们利用HST HUDF/XDF、HUDF 09 -1、HUDF 09 -2、ERS、CANDELS-N和CANDELS-S数据集，在很宽的红移z~4-8和光度范围内，测量了4000多个高红移星系的紫外连续谱斜率β。我们的新β结果在z~4（-15.5等：0.006 L*（z=3））、z~5（-16.5等：0.014 L *（z=3））以及z~6和z~7（-17等：0.025 L*（z=3））处达到非常微弱的水平。先前研究之间的相互影响使我们对系统误差进行了全面审查，并开发了一种新的技术来测量β，该技术对噪声影响产生的偏差具有鲁棒性。我们通过逐对象比较证明，所有以前的研究，包括我们自己的研究和在最新的HUDF 12数据集上进行的研究，都存在β的小系统误差。我们发现，在校正了系统误差（通常d（beta）~0.1-0.2）之后，来自不同组的在z~7处的所有beta结果都非常一致。我们测量的微弱信号的平均β（-18 mag：0.1L*（z=3））z~4，z~5，z~6和z~7星系的平均值为-2.03+/-0.03+/-0.06（随机误差和系统误差）分别为-2.14+/-0.06+/-0.06、-2.24+/-0.11+/-0.08和-2.30+/-0.18+/-0.13。我们的新β值比我们过去报告的更红，但比其他最近的结果更蓝。我们先前报道的在低光度下更蓝的β的趋势得到了证实，在高红移下向更蓝的β的演变也是如此。β似乎只表现出M（UV，AB）~ -19等的微弱光度依赖性，表明对于z>~4的微弱星系，β的平均渐近线为~ -2.2 ~-2.4。在z~7处，观测到的β表明非零，但低尘埃消光，它们与宇宙流体动力学模拟中预测的值吻合得很好。
英文摘要：
We measure the UV-continuum slope beta for over 4000 high-redshift galaxies over a wide range of redshifts z~4-8 and luminosities from the HST HUDF/XDF, HUDF09-1, HUDF09-2, ERS, CANDELS-N, and CANDELS-S data sets. Our new beta results reach very faint levels at z~4 (-15.5 mag: 0.006 L*(z=3)), z~5 (-16.5 mag: 0.014L*(z=3)), and z~6 and z~7 (-17 mag: 0.025 L*(z=3)). Inconsistencies between previous studies led us to conduct a comprehensive review of systematic errors and develop a new technique for measuring beta that is robust against biases that arise from the impact of noise. We demonstrate, by object-by-object comparisons, that all previous studies, including our own and those done on the latest HUDF12 dataset, suffer from small systematic errors in beta. We find that after correcting for the systematic errors (typically d(beta) ~0.1-0.2) all beta results at z~7 from different groups are in excellent agreement. The mean beta we measure for faint (-18 mag: 0.1L*(z=3)) z~4, z~5, z~6, and z~7 galaxies is -2.03+/-0.03+/-0.06 (random and systematic errors), -2.14+/-0.06+/-0.06, -2.24+/-0.11+/-0.08, and -2.30+/-0.18+/-0.13, respectively. Our new beta values are redder than we have reported in the past, but bluer than other recent results. Our previously reported trend of bluer beta's at lower luminosities is confirmed, as is the evolution to bluer beta's at high redshifts. beta appears to show only a mild luminosity dependence faintward of M(UV,AB) ~ -19 mag, suggesting that the mean beta asymptotes to ~ -2.2 to -2.4 for faint z>~4 galaxies. At z~7, the observed beta's suggest non-zero, but low dust extinction, and they agree well with values predicted in cosmological hydrodynamical simulations.
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