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Spectroscopic quantification of projection effects in the SDSS redMaPPer galaxy cluster catalogue
Monthly Notices of the Royal Astronomical Society ( IF 4.8 ) Pub Date : 2021-04-30 , DOI: 10.1093/mnras/stab1243
J Myles 1, 2, 3 , D Gruen 1, 2, 3 , A B Mantz 1, 3 , S W Allen 1, 2, 3 , R G Morris 1, 2, 3 , E Rykoff 2, 3 , M Costanzi 4, 5, 6 , C To 1, 2, 3 , J DeRose 7, 8 , R H Wechsler 1, 2, 3 , E Rozo 9 , T Jeltema 8, 10 , E R Carrasco 11 , A Kremin 12 , R Kron 13
Affiliation  

Projection effects, whereby galaxies along the line of sight to a galaxy cluster are mistakenly associated with the cluster halo, present a significant challenge for optical cluster cosmology. We use statistically representative spectral coverage of luminous galaxies to investigate how projection effects impact the low-redshift limit of the Sloan Digital Sky Survey (SDSS) redMaPPer galaxy cluster catalogue. Spectroscopic redshifts enable us to differentiate true cluster members from false positives and determine the fraction of candidate cluster members viewed in projection. Our main results can be summarized as follows: first, we show that a simple double-Gaussian model can be used to describe the distribution of line-of-sight velocities in the redMaPPer sample; secondly, the incidence of projection effects is substantial, accounting for ∼16 per cent of the weighted richness for the lowest richness objects; thirdly, projection effects are a strong function of richness, with the contribution in the highest richness bin being several times smaller than for low-richness objects; fourthly, our measurement has a similar amplitude to state-of-the-art models, but finds a steeper dependence of projection effects on richness than these models; and fifthly, the slope of the observed velocity dispersion–richness relation, corrected for projection effects, implies an approximately linear relationship between the true, three-dimensional halo mass and three-dimensional richness. Our results provide a robust, empirical description of the impact of projection effects on the SDSS redMaPPer cluster sample and exemplify the synergies between optical imaging and spectroscopic data for studies of galaxy cluster astrophysics and cosmology.

中文翻译:

SDSS redMaPPer星系团目录中投影效应的光谱量化

投影效应,即沿着星系团视线的星系被错误地与星团晕相关联,这对光学星团宇宙学提出了重大挑战。我们使用具有统计代表性的发光星系光谱覆盖来研究投影效应如何影响斯隆数字巡天 (SDSS) redMaPPer 星系团目录的低红移极限。光谱红移使我们能够区分真正的集群成员和误报,并确定在投影中查看的候选集群成员的比例。我们的主要结果可以总结如下:首先,我们展示了一个简单的双高斯模型可以用来描述 redMaPPer 样本中视线速度的分布;其次,投影效应的发生率很高,占最低丰富度对象的加权丰富度的 16%;第三,投影效果是丰富度的强函数,在最高丰富度箱中的贡献比低丰富度对象小几倍;第四,我们的测量与最先进的模型具有相似的幅度,但发现投影效果对丰富度的依赖性比这些模型更陡峭;第五,观测到的速度色散-丰富度关系的斜率,校正了投影效应,暗示了真实的三维晕质量和三维丰富度之间的近似线性关系。我们的结果提供了一个稳健的、
更新日期:2021-04-30
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