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arXiv 1104.2089astro-ph.CO
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具有约化散射的鲁棒光学丰度估计

Robust Optical Richness Estimation with Reduced Scatter

E. S. Rykoff, B. P. Koester, E. Rozo, J. Annis, A. E. Evrard, S. M. Hansen, J. Hao, D. E. Johnston, T. A. McKay, R. H. Wechsler

摘要:

减少星系团质量和光学丰度之间的散射是光度星表中星系团宇宙学的一个关键目标。我们考虑对Rozo等人(2009)的红色序列匹配滤波器丰富度估计器的各种修改,并评估其对固定丰富度下X射线光度散射的影响。最重要的是,我们发现更深的光度削减可以减少恢复的散射,发现sigma_lnLX|对于M_500c >~ 1.6e14 h_70^-1 M_sun的星系团,λ =0.63+/-0.02。在固定丰度下,相应的质量分散度为sigma_lnM| λ ~ 0.2-0.3,取决于丰度,与总X射线光度相当。我们发现,包括蓝色星系的丰富度估计增加了散射,因为没有加权星系的光学光度。我们进一步证明,我们的丰富度估计是非常强大的。具体地,在估计丰富度时采用的滤波器可以直接从数据校准,而不需要红色序列的先验校准。我们还表明,恢复的丰富性是强大的高达50%的不确定性,在星系背景,以及选择光度过滤器,只要过滤器跨越4000 A的红色序列星系的休息。因此,我们的丰富度估计器可以用来比较不同集群的丰富度估计,即使它们不共享相同的光度数据。附录1包括用于实现我们的最佳丰富度估计器的“easy-bake”指令,我们正在发布一个与SDSS数据一起工作的代码实现,以及一个增强的maxBCG目录,其中包含为每个集群测量的lambda丰富度。

英文摘要:

Reducing the scatter between cluster mass and optical richness is a key goal for cluster cosmology from photometric catalogs. We consider various modifications to the red-sequence matched filter richness estimator of Rozo et al. (2009), and evaluate their impact on the scatter in X-ray luminosity at fixed richness. Most significantly, we find that deeper luminosity cuts can reduce the recovered scatter, finding that sigma_lnLX|lambda=0.63+/-0.02 for clusters with M_500c >~ 1.6e14 h_70^-1 M_sun. The corresponding scatter in mass at fixed richness is sigma_lnM|lambda ~ 0.2-0.3 depending on the richness, comparable to that for total X-ray luminosity. We find that including blue galaxies in the richness estimate increases the scatter, as does weighting galaxies by their optical luminosity. We further demonstrate that our richness estimator is very robust. Specifically, the filter employed when estimating richness can be calibrated directly from the data, without requiring a-priori calibrations of the red-sequence. We also demonstrate that the recovered richness is robust to up to 50% uncertainties in the galaxy background, as well as to the choice of photometric filter employed, so long as the filters span the 4000 A break of red-sequence galaxies. Consequently, our richness estimator can be used to compare richness estimates of different clusters, even if they do not share the same photometric data. Appendix 1 includes "easy-bake" instructions for implementing our optimal richness estimator, and we are releasing an implementation of the code that works with SDSS data, as well as an augmented maxBCG catalog with the lambda richness measured for each cluster.

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