Galaxies at [FORMULA][F]z~7-8[/F][/FORMULA]: [FORMULA][F]z[INF]850[/INF][/F][/FORMULA]-Dropouts in the Hubble Ultra Deep Field
Galaxies at [FORMULA][F]z~7-8[/F][/FORMULA]: [FORMULA][F]z[INF]850[/INF][/F][/FORMULA]-Dropouts in the Hubble Ultra Deep Field
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[FORMULA][F]z~7-8[/F][/FORMULA] 处的星系：[FORMULA][F]z[INF]850[/INF][/F][/FORMULA]-哈勃望远镜中的漏失
DOI：
10.1086/426503
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
M. Rieke
中科院分区：
文献类型：
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作者：
R. Bouwens;R. Thompson;G. Illingworth;M. Franx;P. V. Dokkum;Xiaohui Fan;M. Dickinson;D. Eisenstein;M. Rieke
我们在哈勃超深场的144“x144”NICMOS观测中发现了大约z~7-8个星系。该样品的选择标准为(z-J)>0.8, (z-J)> 0.66 (J- h)+0.8, (J- h)<1.2, <8500埃无检测。选取的5个震源的总星等为H~27。与典型的低红移消失星系相比，五个源中的四个是相当蓝的，并且聚集在1角分**2区域内。由于所有5个来源都接近NICMOS数据的极限，我们仔细评估了它们的真实性。在数据的不同分割和中位数堆栈中可以看到每个候选项。我们分析了一些噪声图像，估计杂散源的数量为1+/-1。使用同一数据集的独立约简进行搜索，清楚地显示了5个候选者中的3个，并且微弱地发现了第4个候选者，这表明污染可能更高。为了与低红移样本的预测结果进行比较，我们采用保守方法，选取了4个z~7-8星系作为样本。在模拟数据集上使用相同的检测标准，假设从z~3.8没有进化，我们预测z~7-8处有10个源，如果我们使用更现实的（1+z）^{-1}大小缩放，我们预测14个源。我们估计在z~7.5处（积分到0.3L*）的静帧连续UV（~1800埃）光度密度仅为z~3.8处的0.20_{-0.08}^{+0.12}x。这有效地将亮度密度的上限设置为0.3 L*。这一结果与亮度函数从z~7.5到z~3.8的显著演化一致。即使在z~7.5的较低紫外光度密度下，星系似乎仍然可以在这些红移的再电离中发挥重要作用，尽管还需要进行明确的测量。(简略)
We have detected likely z~7-8 galaxies in the 144"x144" NICMOS observations of the Hubble Ultra Deep Field. Objects are required to be >3 sigma detections in both NICMOS bands, J and H. The selection criteria for this sample are (z-J)>0.8, (z-J) > 0.66 (J-H)+0.8, (J-H)<1.2, and no detection at <8500 Angstroms. The 5 selected sources have total magnitudes H~27. Four of the five sources are quite blue compared to typical lower-redshift dropout galaxies and are clustered within a 1 arcmin**2 region. Because all 5 sources are near the limit of the NICMOS data, we have carefully evaluated their reality. Each of the candidates is visible in different splits of the data and a median stack. We analyzed several noise images and estimate the number of spurious sources to be 1+/-1. A search using an independent reduction of this same data set clearly revealed 3 of the 5 candidates and weakly detected a 4th candidate, suggesting the contamination could be higher. For comparison with predictions from lower redshift samples we take a conservative approach and adopt four z~7-8 galaxies as our sample. With the same detection criteria on simulated datasets, assuming no-evolution from z~3.8, we predict 10 sources at z~7-8, or 14 if we use a more realistic (1+z)^{-1} size scaling. We estimate that the rest-frame continuum UV (~1800 Angstroms) luminosity density at z~7.5 (integrated down to 0.3L*) is just 0.20_{-0.08}^{+0.12}x that found at z~3.8. Effectively this sets an upper limit on the luminosity density down to 0.3 L*. This result is consistent with significant evolution at the bright end of the luminosity function from z~7.5 to z~3.8. Even with the lower UV luminosity density at z~7.5, it appears that galaxies could still play an important role in reionization at these redshifts, though definitive measurements remain to be made. [abridged]