Magellan/M2FS Spectroscopy of Galaxy Clusters: Stellar Population Model and Application to Abell 267

Abstract

We report the results of a pilot program to use the Magellan/M2FS spectrograph to survey the galactic populations and internal kinematics of galaxy clusters. For this initial study, we present spectroscopic measurements for $223$ quiescent galaxies observed along the line of sight to the galaxy cluster Abell 267 ($z\sim0.23$). We develop a Bayesian method for modeling the integrated light from each galaxy as a simple stellar population, with free parameters that specify redshift ($v_\mathrm{los}/c$) and characteristic age, metallicity ($\mathrm{[Fe/H]}$), alpha-abundance ($[α/\mathrm{Fe}]$), and internal velocity dispersion ($σ_\mathrm{int}$) for individual galaxies. Parameter estimates derived from our 1.5-hour observation of A267 have median random errors of $σ_{v_\mathrm{los}}=20\ \mathrm{km\ s^{-1}}$, $σ_{\mathrm{Age}}=1.2\ \mathrm{Gyr}$, $σ_{\mathrm{[Fe/H]}}=0.11\ \mathrm{dex}$, $σ_{[α/\mathrm{Fe}]}=0.07\ \mathrm{dex}$, and $σ_{σ_\mathrm{int}}=20\ \mathrm{km\ s^{-1}}$. In a companion paper, we use these results to model the structure and internal kinematics of A267.

16 pages, 11 figures, accepted for publication in The Astronomical Journal