A Complete Spectroscopic Census of Abell 2029: A Tale of Three Histories

TL;DR

This study provides a comprehensive spectroscopic analysis of Abell 2029 and its infalling groups, revealing galaxy evolution patterns, metallicity differences, and the impact of cluster dynamics on galaxy properties.

Contribution

It offers the first complete spectroscopic census of Abell 2029, identifying galaxy types, infall groups, and their evolutionary states with detailed metallicity and age analyses.

Findings

Infall groups are confirmed via spectroscopic, X-ray, and weak lensing data.

Members within certain mass ranges are more metal-rich than similar SDSS galaxies.

Galaxy ages and properties vary with clustercentric distance, indicating stochastic evolution effects.

Abstract

A rich spectroscopic census of members of the local massive cluster Abell 2029 includes 1215 members of A2029 and its two infalling groups, A2033 and a Southern Infalling Group (SIG). The two infalling groups are identified in spectroscopic, X-ray and weak lensing maps. We identify active galactic nuclei (AGN), star-forming galaxies, E+A galaxies, and quiescent galaxies based on the spectroscopy. The fractions of AGN and post-starburst E+A galaxies in A2029 are similar to those of other clusters. We derive the stellar mass ($M_{*}$)-metallicity of A2029 based on 227 star-forming members; A2029 members within $10^{9} M_{\odot} < M _{*} < 10^{9.5} M_{\odot}$ are more metal rich than SDSS galaxies within the same mass range. We utilize the spectroscopic index $D_{n}4000$, a strong age indicator, to trace past and future evolution of the A2029 system. The median $D_{n}4000$ of the members decreases as the projected clustercentric distance increases for all three subsystems. The $D_{n}4000 - M_{*}$ relations of the members in A2029 and its two infalling groups differ significantly indicating the importance of stochastic effects for understanding the evolution of cluster galaxy populations. In the main cluster, an excess around $D_{n}4000 \sim 1.8$ indicates that some A2029 members became quiescent galaxies 2-3 Gyr ago consistent with the merger epoch of the X-ray sloshing pattern.