King Ghidorah Supercluster: Mapping the light and dark matter in a new supercluster at z=0.55 using the Subaru Hyper Suprime-Cam

TL;DR

This paper reports the discovery of the King Ghidorah Supercluster at z=0.55, mapping its galaxy and dark matter distribution using Subaru Hyper Suprime-Cam data, revealing its massive scale and complex structure.

Contribution

It presents the first detection and detailed mapping of the most massive supercluster at z>0.5 using wide-field weak lensing and galaxy data from HSC-SSP.

Findings

Supercluster mass estimated at 10^16 solar masses

Detected triple weak-lensing peaks over 70 Mpc

Overdensity of red-sequence clusters with δ=14.7±4.5

Abstract

This paper reports our discovery of the most massive supercluster, termed the King Ghidorah Supercluster (KGSc), at $z=0.50-0.64$ in the Third Public Data Release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP PDR3) over 690 deg$^2$, as well as an initial result for a galaxy and dark matter mapping. The primary structure of the KGSc comprises triple broad weak-lensing (WL) peaks over 70 comoving Mpc. Such extensive WL detection at $z>0.5$ can only currently be achieved using the wide-field high-quality images produced by the HSC-SSP. The structure is also contiguous with multiple large-scale structures across a $\sim400$ comoving Mpc scale. The entire field has a notable overdensity ($\delta=14.7\pm4.5$) of red-sequence clusters. Additionally, large-scale underdensities can be found in the foreground along the line of sight. We confirmed the overdensities in stellar mass and dark matter distributions to be tightly coupled and estimated the total mass of the main structure to be $1\times10^{16}$ solar masses, according to the mock data analyses based on large-volume cosmological simulations. Further, upcoming wide-field multi-object spectrographs such as the Subaru Prime Focus Spectrograph may aid in providing additional insights into distant superclusters beyond the 100 Mpc scale.