The Complex Structure of the Cl 1604 Supercluster at z~0.9

TL;DR

This study maps the three-dimensional structure of the Cl 1604 supercluster at z~0.9, revealing its complex composition, including multiple clusters, filaments, and background structures, through extensive spectroscopic observations.

Contribution

The paper provides the first detailed 3D mapping of the Cl 1604 supercluster at z~0.9, including velocity dispersions and analysis of overlapping structures, using a large spectroscopic dataset.

Findings

Mapped the complex 3D structure of Cl 1604 supercluster.

Identified additional structures along the line-of-sight, including filaments and background clusters.

Analyzed biases in velocity dispersion measurements due to overlapping structures.

Abstract

The Cl1604 supercluster at z=0.9 is one of a small handful of such structures discovered in the high redshift universe, and is the first target observed as part of the Observations of Redshift Evolution in Large Scale Environments (ORELSE) Survey. To date, Cl1604 is the largest structure mapped at z~1, with the most constituent clusters and the largest number of spectroscopically confirmed member galaxies. In this paper we present the results of a spectroscopic campaign to create a three-dimensional map of Cl1604 and to understand the contamination by fore- and background large scale structures. Combining new Deep Imaging Multi-object Spectrograph observations with previous data yields redshifts for 1,383 extragalactic objects in a ~ 0.08 sq. deg region, 449 of which are supercluster members. We examine the complex three dimensional structure of Cl1604, providing velocity dispersions for eight of the member clusters and groups. Our extensive spectroscopic dataset is used to examine potential biases in cluster velocity dispersion measurements in the presence of overlapping structures and filaments. We also discuss other structures found along the line-of-sight, including a filament at z=0.6 and two serendipitously discovered clusters/groups at z~1.2.