Identification of a high redshift cluster in the field of Q2345+007 through deep BRIJK' photometry

TL;DR

This study identifies a high-redshift galaxy cluster at z~0.75 near Q2345+007 using deep optical and near-infrared photometry, revealing an overdensity of galaxies and a potential gravitational lensing structure.

Contribution

It introduces a new combined optical and near-IR photometric method with statistical analysis to detect and characterize high-redshift galaxy clusters.

Findings

Detected a galaxy overdensity at z~0.75

Identified a potential gravitational lens responsible for the quasar lensing

Most cluster candidates are star-forming or burst systems 1-3 Gyr old

Abstract

This paper describes new results on the identification of the complex gravita- tional lens responsible for the double quasar Q2345+007. A gravitational shear field was detected recently about 45'' away from the QSO, centered on an excess of faint blue galaxies. We present deep photometric data in the near-IR (J & K'), which are used together with optical BRI photometry to build spectral ener- gy distributions for all the objects, and to derive a photometric redshift esti- mate by comparison with synthetic spectrophotometric data. We propose a statis- tical method to analyse the distribution in z. An excess of galaxies at z about 0.75 is detected in this field, with a 2D distribution showing a maximum located at the center of the weak-shear field. The z inferred for this overdensity (a distant cluster of galaxies) corresponds to an absorption system in the spectrum of the quasar B. Most cluster-member candidates at z=0.75 are undergoing a star- formation process or are burst systems 1 to 3 Gyr old. We also discuss the exis- tence of other possible excesses of galaxies at different z planes.