Subaru Hyper Suprime-Cam excavates colossal over- and under-dense structures over 360 deg2 out to z=1

TL;DR

This study utilizes Subaru's Hyper Suprime-Cam data to identify and analyze massive over- and under-dense cosmic structures up to redshift 1 over 360 square degrees, confirming known superclusters and discovering new colossal regions.

Contribution

It presents the first large-scale detection and characterization of extensive over- and under-dense structures at z=0.3-1 using wide-field photometric data, including weak lensing analysis.

Findings

Confirmed known superclusters

Identified new colossal over- and under-dense regions

Weak lensing signals correlate with density peaks and troughs

Abstract

Subaru Strategic Program with the Hyper-Suprime Cam (HSC-SSP) has proven to be successful with its extremely-wide area coverage in past years. Taking advantages of this feature, we report initial results from exploration and research of expansive over- and under-dense structures at $z=$ 0.3-1 based on the second Public Data Release where optical 5-band photometric data for $\sim$ eight million sources with $i<23$ mag are available over $\sim360$ square degrees. We not only confirm known superclusters but also find candidates of titanic over- and under-dense regions out to $z=1$. The mock data analysis suggests that the density peaks would involve one or more massive dark matter haloes ($>10^{14}$ M$_\odot$) of the redshift, and the density troughs tend to be empty of massive haloes over $>10$ comoving Mpc. Besides, the density peaks and troughs at $z<0.6$ are in part identified as positive and negative weak lensing signals respectively, in mean tangential shear profiles, showing a good agreement with those inferred from the full-sky weak lensing simulation. The coming extensive spectroscopic surveys will be able to resolve these colossal structures in three-dimensional space. The number density information over the entire survey field will be available as grid-point data on the website of the HSC-SSP data release (https://hsc.mtk.nao.ac.jp/ssp/data-release/).