IDCS J1433.2+3306: An IR-Selected Galaxy Cluster at z = 1.89

TL;DR

This paper reports the discovery and spectroscopic confirmation of a galaxy cluster at redshift 1.89, highlighting its star formation activity and stellar population characteristics, which provide insights into cluster evolution at high redshift.

Contribution

The paper presents the first spectroscopic confirmation of an IR-selected galaxy cluster at z=1.89 with detailed star formation and stellar age analysis.

Findings

Confirmed cluster at z=1.89 with spectroscopic data

Detected high star formation rates in member galaxies

Identified a red sequence indicating mature stellar populations

Abstract

We report the discovery of an IR-selected galaxy cluster in the IRAC Distant Cluster Survey (IDCS). New data from the Hubble Space Telescope spectroscopically confirm IDCS J1433.2+3306 at z = 1.89 with robust spectroscopic redshifts for seven members, two of which are based on the 4000 Angstrom break. Detected emission lines such as [OII] and Hbeta indicate star formation rates of >20 solar masses per year for three galaxies within a 500 kpc projected radius of the cluster center. The cluster exhibits a red sequence with a scatter and color indicative of a formation redshift z > 3.5. The stellar age of the early-type galaxy population is approximately consistent with those of clusters at lower redshift (1 < z < 1.5) suggesting that clusters at these redshifts are experiencing ongoing or increasing star formation.