A Complete Spectroscopic Census of A2029: A Tale of Three Histories

Abstract

A rich spectroscopic census of members of the local massive cluster A2029 includes 1215 members of A2029 and its two infalling groups, A2033 and the Southern Infalling Group. The two infalling groups are identified in spectroscopic, X-ray, and weak-lensing maps. We identify active galactic nuclei (AGNs), 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 relation of A2029 based on 227 star-forming members; A2029 members within 10(9) M-circle dot < M-* < 10(9.5) M-circle dot are more metal-rich than Sloan Digital Sky Survey 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.