SDSS-IV Cosmic Web Catalog

This repository contains the cosmic web catalog data released in the paper "Cosmic Web Catalog on SDSS-IV Data with SCONCE" (preparing). The catalog is constructed on the SDSS-IV galaxies and quasars (QSO) using our proposed Directional Subspace Constrained Mean Shift (DirSCMS) algorithm. We release both the cosmic filaments and local modes (i.e., local maxima of the estimated galaxy/QSO density field, which serves as candidates of galaxy clusters) within 325 thin redshift slices, each of which spans 20Mpc under the Planck15 cosmology. The entire catalog covers the redshift range from \(z=0\) to \(z=3\). 1. "<strong>Cosmic_filaments_2D_DirSCMS_new1</strong>": The file contains some discrete realizations of the estimated cosmic filaments in some particular redshift slices. The meaning of each column in the file is described as follows: <strong>RA</strong> -- right ascension. <strong>DEC</strong> -- declination. <strong>z_low</strong> -- lower limit of the redshift slice. <strong>z_high</strong> -- upper limit of the redshift slice. <strong>comov_dist_low</strong> -- lower limit of the comoving distance in the redshift slice under the Planck15 cosmology. <strong>comov_dist_high</strong> -- upper limit of the comoving distance in the redshift slice under the Planck15 cosmology. <strong>bw</strong> -- smoothing bandwidth parameter for the DirSCMS algorithm in the redshift slice. <strong>unc_meas</strong> -- uncertainty measure of the filamentary point by the nonparametric bootstrap techinque. <strong>density</strong> -- (proportional) estimated galaxy/QSO density value at the filamentary point. <strong>grad_Dir1</strong> -- (Riemannian) gradient of the estimated density field (first direction). <strong>grad_Dir2</strong> -- (Riemannian) gradient of the estimated density field (second direction). <strong>grad_Dir3</strong> -- (Riemannian) gradient of the estimated density field (third direction). <strong>knot_label</strong> -- indicator of whether the filamentary point is a knot (i.e., the intersection of several filaments) or not. 2. "<strong>Cosmic_local_modes_2D_DirMS_unique1</strong>": The file contains some discrete realizations of the estimated local modes in some particular redshift slices. The columns are subsumed by the ones in the cosmic filament file and has been described above. <em>Additional notes: We provide both the "csv" and "fits" format for each of the above file.</em> Please cite the paper when using the data in this repository. ► Pure catalog data: [1] <strong>Cosmic Web Catalog on SDSS-IV Data with SCONCE</strong>. (In preparation) ►Methodology: [1] Yikun Zhang, Rafael S. de Souza, and Yen-Chi Chen (2022). <strong>SCONCE: A Cosmic Web Finder for Spherical and Conic Geometries</strong>. <em>arXiv preprint arXiv:2207.07001</em> [2] Yikun Zhang and Yen-Chi Chen (2022) <strong>Linear Convergence of the Subspace Constrained Mean Shift Algorithm: From Euclidean to Directional Data</strong>. <em>Information and Inference: A Journal of the IMA</em>, iaac005, https://doi.org/10.1093/imaiai/iaac005 [3] Yikun Zhang and Yen-Chi Chen (2021) <strong>Kernel Smoothing, Mean Shift, and Their Learning Theory with Directional Data</strong>. <em>Journal of Machine Learning Research</em> <strong>22</strong>(154): 1-92.

本仓库包含发表于论文《基于SDSS-IV数据与SCONCE的宇宙网目录》（待刊）的宇宙网目录数据。该目录基于SDSS-IV的星系与类星体（quasars, QSO）构建，采用我们提出的定向子空间约束均值漂移（Directional Subspace Constrained Mean Shift，简称DirSCMS）算法。本数据集包含325个薄红移切片内的宇宙丝状物与局域模式（即估计的星系/类星体密度场的局域极大值，可作为星系团候选体），每个红移切片在Planck15宇宙学下跨度为20百万秒差距（Mpc）。整个目录的红移覆盖范围为z=0至z=3。
1. "Cosmic_filaments_2D_DirSCMS_new1"：该文件包含部分特定红移切片中估计的宇宙丝状物的离散采样点。文件各列含义如下：<strong>RA</strong> -- 赤经（right ascension）；<strong>DEC</strong> -- 赤纬（declination）；<strong>z_low</strong> -- 红移切片下限；<strong>z_high</strong> -- 红移切片上限；<strong>comov_dist_low</strong> -- Planck15宇宙学下该红移切片的共动距离下限；<strong>comov_dist_high</strong> -- Planck15宇宙学下该红移切片的共动距离上限；<strong>bw</strong> -- 该红移切片下DirSCMS算法的平滑带宽参数；<strong>unc_meas</strong> -- 非参数自助法（bootstrap）技术得到的丝状物点的不确定性度量；<strong>density</strong> -- 该丝状物点处的（比例化）估计星系/类星体密度值；<strong>grad_Dir1</strong> -- 估计密度场的（黎曼）梯度（第一方向）；<strong>grad_Dir2</strong> -- 估计密度场的（黎曼）梯度（第二方向）；<strong>grad_Dir3</strong> -- 估计密度场的（黎曼）梯度（第三方向）；<strong>knot_label</strong> -- 该丝状物点是否为结点（即多条丝状物的交点）的标识。
2. "Cosmic_local_modes_2D_DirMS_unique1"：该文件包含部分特定红移切片中估计的局域模式的离散采样点。其列字段与上述宇宙丝状物文件一致，前文已详述。
*附加说明：我们为上述所有文件均提供了csv与fits两种格式。使用本仓库的数据时，请引用相关论文。
► 纯目录数据：[1] 《基于SDSS-IV数据与SCONCE的宇宙网目录》（待刊）
► 方法学：[1] Yikun Zhang, Rafael S. de Souza, 与 Yen-Chi Chen (2022). 《SCONCE：面向球面与锥面几何的宇宙网探测工具》. arXiv预印本arXiv:2207.07001
[2] Yikun Zhang与Yen-Chi Chen (2022) 《子空间约束均值漂移算法的线性收敛性：从欧氏数据到定向数据》. 《信息与推断：IMA期刊》, iaac005, https://doi.org/10.1093/imaiai/iaac005
[3] Yikun Zhang与Yen-Chi Chen (2021) 《定向数据下的核平滑、均值漂移及其学习理论》. 《机器学习研究期刊》, 22(154): 1-92.