Oral Presentation

Full-sky Density Reconstruction for Cluster and Protocluster Searches

Author(s): Yi-Kuan Chiang (ASIAA)

Presenter: Yi-Kuan Chiang (ASIAA)

I will introduce an exciting new technique to optimally combine full-sky photometric surveys, such as WISE and SPHEREx, with large spectroscopic surveys including SDSS, BOSS, eBOSS, and DESI, to reconstruct the extragalactic density field. As a first demonstration (Chiang 2023, arXiv:2306.03926), we created a 2D projected map of large-scale structure (LSS) by extracting extragalactic fluctuations embedded in the 100 μm cosmic infrared background (CIB), using tomographic cross-correlations between over 600 million WISE galaxies and 3 million spectroscopic redshifts. The reconstructed field reproduces all high-dimensional tomographic two-point statistics of the CIB and spans the largest sky coverage of any LSS reconstruction to date. It identifies a rich population of massive clusters, including all Abell clusters as well as others not in existing catalogs. This all-purpose density field supports a wide range of cosmological and astrophysical applications, including full-sky searches for clusters and protoclusters. The method is readily extendable to higher redshifts. We aim to develop a full 3D reconstruction with percent-level redshift precision by combining SPHEREx templates with DESI spectroscopy. This will enable cluster and protocluster searches out to z = 2–3, offering both an unprecedented statistical sample and the chance to discover the single most massive structure in the observable universe.