Imaging and Modeling Data from the Hydrogen Epoch of Reionization Array
C. L. Carilli{1, 2}, N. Thyagarajan{1}, J. Kent{2}, B. Nikolic{2}, K. Gale-Sides{2}, N. S. Kern{3}, G. Bernardi{4, 5, 6}, A. Mesinger{7}, S. Matika{5}, the HERA… 展开作者
C. L. Carilli{1, 2}, N. Thyagarajan{1}, J. Kent{2}, B. Nikolic{2}, K. Gale-Sides{2}, N. S. Kern{3}, G. Bernardi{4, 5, 6}, A. Mesinger{7}, S. Matika{5}, the HERA TEAM {1}{National Radio Astronomy Observatory, P. O. Box 0, Socorro, NM 87801, USA, ccarilli@nrao. edu, ORCID, :, 0000-0001-6647-3861} {2}{Astrophysics Group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK} {3}{Department of Astronomy, University of California, Berkeley, CA} {4}{INAF-Istituto di Radioastronomia, via Gobetti 101, 40129, Bologna, Italy} {5}{Department of Physics, Electronics, Rhodes University, PO Box 94, Grahamstown, 6140, South Africa} {6}{The South African Radio Astronomy Observatory, 2 Fir Street, Black River Park, Observatory, 7925, South Africa} {7}{Scuola Normale Superiore, 56126 Pisa, PI, Italy}
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17 pages, 10 figures, accepted for the ApJ Supplement
We analyze data from the Hydrogen Epoch of Reionization Array. This is the third in a series of papers on the closure phase delay-spectrum technique designed to detect the HI 21cm emission from cosmic reionization. We present the details of the data and models employed in the power spectral analysis, and discuss limitations to the process. We compare images and visibility spectra made with HERA data, to parallel quantities generated from sky models based on the GLEAM survey, incorporating the HERA telescope model. We find reasonable agreement between images made from HERA data, with those generated from the models, down to the confusion level. For the visibility spectra, there is broad agreement between model and data across the full band of $\sim 80$MHz. However, models with only GLEAM sources do not reproduce a roughly sinusoidal spectral structure at the tens of percent level seen in the observed visibility spectra on scales $\sim 10$ MHz on 29 m baselines. We find that this structure is likely due to diffuse Galactic emission, predominantly the Galactic plane, filling the far sidelobes of the antenna primary beam. We show that our current knowledge of the frequency dependence of the diffuse sky radio emission, and the primary beam at large zenith angles, is inadequate to provide an accurate reproduction of the diffuse structure in the models. We discuss implications due to this missing structure in the models, including calibration, and in the search for the HI 21cm signal, as well as possible mitigation techniques.
New Limits on Polarized Power Spectra at 126 and 164 MHz: Relevance to Epoch of Reionization Measurements
偏振前景发射是测量高红移21 cm HI再电离期涨落功率谱的一个潜在的污染源。使用Donald C。Backer精密阵列探测再电离时期（PAPER），我们提出了在两个频段，以126 MHz为中心的所有四个斯托克斯参数的观测功率谱的限制（$z=10.3$）和164 MHz（$z=7.66$）进行为期三个月的观测活动，部署32个天线，在$z=7.7$（Parsons et al 2014）和$7.5 < z < 10.5$（Jacobs et al 2014）中报告了非偏振功率谱结果。本文中的功率谱的处理方式与那些作品中的相同，并且没有显示出偏振功率的确定性检测。这种未检测到的现象似乎主要是由于电离层旋转测量波动对极化功率的抑制，这强烈影响了斯托克斯Q和U。我们能够证明，在Parsons等人2014年和Jacobs等人2014年报告的限值水平下，极化泄漏的净效应可以忽略不计。
