A Comparison of Three Elliptical Galaxy Photo-chemical Evolution Codes

Working within the classic supernovae-driven wind framework for elliptical galaxy evolution, we perform a systematic investigation into the discrepancies between the predictions of three contemporary codes – Arimoto & Yoshii (1987, A&A, 173, 23), Bressan et al. (1994, ApJS, 94, 63), and Gibson (1996a, MNRAS, 278, 829; 1996b, MNRAS, submitted). By being primarily concerned with reproducing the present-day colour-metallicity-luminosity (CML) relations amongst ellipticals, the approaches taken in the theoretical modelling have managed to obscure many of the hidden differences between the codes. Targeting the timescale for the onset of the initial galactic wind tGW as a primary “difference” indicator, we demonstrate exactly how and why each code is able to claim successful reproduction of the CML relations, despite possessing apparently incompatible input ingredients. Subject headings: galaxies: abundances — galaxies: elliptical and lenticular, cD — galaxies: evolution — methods: miscellaneous