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

Jubee Sohn, Margaret J. Geller, H. Jabran Zahid, Daniel G. Fabricant
2019 Astrophysical Journal  
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
more » ... . We derive the stellar mass (M_*)-metallicity of A2029 based on 227 star-forming members; A2029 members within 10^9 M_ < M _* < 10^9.5 M_ are more metal rich than SDSS galaxies within the same mass range. We utilize the spectroscopic index D_n4000, a strong age indicator, to trace past and future evolution of the A2029 system. The median D_n4000 of the members decreases as the projected clustercentric distance increases for all three subsystems. The D_n4000 - 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_n4000 ∼ 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.
doi:10.3847/1538-4357/ab0213 fatcat:ai4zay2e7bdwvhyrqpos4n3p5u