Galaxy clustering, photometric redshifts and diagnosis of systematics in the DES Science Verification data
Galaxy clustering, photometric redshifts and diagnosis of systematics in the DES Science Verification data
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DOI：
10.1093/mnras/stv2590
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发表时间：
2015-07
影响因子：
4.8
通讯作者：
M. Crocce;J. Carretero;A. Bauer;A. Ross;I. Sevilla-Noarbe;T. Giannantonio;F. Sobreira;J. Sánchez-J.-S
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文献类型：
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作者：
M. Crocce;J. Carretero;A. Bauer;A. Ross;I. Sevilla-Noarbe;T. Giannantonio;F. Sobreira;J. Sánchez-J.-S
我们在暗能量调查(DES)的科学验证观测中研究了在I<；22.5探测到的星系团。两点相关函数是用2.3×106个星系在相邻的116°区域内测量的，在0.2<；z<；1.2的范围内，光度学红移宽度Deltaz=0.2。通过比较基于模板的PHOTO-Z算法(BPZ)和机器学习算法(TPZ)的结果来评估光度学红移误差的影响。与之配套的一篇论文提供了几个观测变量(例如，观测值、天空亮度)的地图，这些变量可以调节星系的密度。在这里，我们描述和减轻了由这些观测变量引起的测量星团的系统误差，以及其他如银河系尘埃和恒星污染。在对系统效应进行校正后，我们测量了相对于Planck Lambda冷暗物质模型预测的质量星团的广泛线性尺度上的星系偏差，发现与加拿大-法国-夏威夷望远镜遗产调查(CFHTLS)的测量结果一致，Chi2为4.0(8.7)，TPZ(BPZ)红移为5个自由度。我们测试了一个“线性偏差”模型，在这个模型中，星系群是预测的非线性暗物质群的固定倍数。数据的精确度使我们能够确定线性偏差模型描述观测到的星系团的精确度为2.5%，精确度至少比线性理论所期望的尺度小4-10倍。
We study the clustering of galaxies detected at i < 22.5 in the Science Verification observations of the Dark Energy Survey (DES). Two-point correlation functions are measured using 2.3 × 106 galaxies over a contiguous 116 deg2 region in five bins of photometric redshift width Deltaz = 0.2 in the range 0.2 < z < 1.2. The impact of photometric redshift errors is assessed by comparing results using a template-based photo-z algorithm (BPZ) to a machine-learning algorithm (TPZ). A companion paper presents maps of several observational variables (e.g. seeing, sky brightness) which could modulate the galaxy density. Here we characterize and mitigate systematic errors on the measured clustering which arise from these observational variables, in addition to others such as Galactic dust and stellar contamination. After correcting for systematic effects, we measure galaxy bias over a broad range of linear scales relative to mass clustering predicted from the Planck Lambda cold dark matter model, finding agreement with the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) measurements with chi2 of 4.0 (8.7) with 5 degrees of freedom for the TPZ (BPZ) redshifts. We test a `linear bias' model, in which the galaxy clustering is a fixed multiple of the predicted non-linear dark matter clustering. The precision of the data allows us to determine that the linear bias model describes the observed galaxy clustering to 2.5 per cent accuracy down to scales at least 4-10 times smaller than those on which linear theory is expected to be sufficient.