The Physical Properties of Luminous z ≳ 8 Galaxies and Implications for the Cosmic Star Formation Rate Density from ∼0.35 deg2 of (Pure-)Parallel HST Observations
The Physical Properties of Luminous z ≳ 8 Galaxies and Implications for the Cosmic Star Formation Rate Density from ∼0.35 deg2 of (Pure-)Parallel HST Observations
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DOI：
10.3847/1538-4357/ac4803
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发表时间：
2021-06
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通讯作者：
G. Roberts-Borsani;T. Morishita;T. Treu;N. Leethochawalit;M. Trenti
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作者：
G. Roberts-Borsani;T. Morishita;T. Treu;N. Leethochawalit;M. Trenti
我们提出了迄今为止最大的系统，基于哈勃太空望远镜（HST）的搜索，使用来自288条随机视线汇编的（纯）平行观测（1267 arcmin2），使用先进的巡天相机和宽视场相机3观测，这些观测来自（超级）最亮的再电离星系（SuperBoRG）数据集，它们共同代表了比现有的天基数据集大1.12倍的因子。利用近红外（NIR）色切和仔细的照片-z分析，我们在29条独特的视线上发现了31个z≥8的候选星系，并得出了整体星系的特性，如紫外星等和连续斜率、大小和静帧光学特性（如恒星形成率（SFRs）、恒星质量、A v）。利用我们的数据集的（纯）并行性质（使其成为迄今为止最具代表性的数据集之一）和衍生的SFR，我们评估了UV亮度函数（LF）在z ~ 8-10处的明亮端宇宙SFR密度，并使用转换因子测试了光度函数衍生结果的有效性。我们发现我们的方法产生的结果与用LFs导出的结果相当。此外，我们用凯克多目标红外探测光谱仪（MOSFIRE）仪器对五个（超级）BoRG目标进行了后续观测，在y波段观测的bbbb3小时中都没有发现Lyα的证据，与z ~ 8的中性介质一致。我们的结果提供了一个明确的HST遗产，在LF明亮的一端，并提供了一个有价值的基准，以及詹姆斯·韦伯太空望远镜的后续目标。
We present the largest systematic, Hubble Space Telescope (HST)–based search to date for luminous z ≳ 8 galaxy candidates using ∼1267 arcmin2 of (pure-)parallel observations from a compilation of 288 random sightlines with Advanced Camera for Surveys and Wide Field Camera 3 observations, derived from the (Super)Brightest of Reionizing Galaxies (SuperBoRG) data set and together representing a factor ∼1.12× larger than existing space-based data sets. Using near-infrared (NIR) color cuts and careful photo-z analyses, we find 31 z ≳ 8 galaxy candidates over 29 unique sightlines, and derive global galaxy properties such as UV magnitudes and continuum slopes, sizes, and rest-frame optical properties (e.g., star formation rates (SFRs), stellar masses, A v). Taking advantage of the (pure-)parallel nature of our data set—making it one of the most representative thus far—and derived SFRs, we evaluate the cosmic SFR density for the bright end of the UV luminosity function (LF) at z ∼ 8–10 and test the validity of luminosity-function-derived results using a conversion factor. We find that our method yields comparable results to those derived with LFs. Furthermore, we present follow-up observations of five (Super)BoRG targets with the Keck Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) instrument, finding no evidence of Lyα in >3 hr of Y-band observations in either, consistent with a largely neutral medium at z ∼ 8. Our results offer a definitive HST legacy on the bright end of the LF and provide a valuable benchmark as well as targets for follow-up with the James Webb Space Telescope.