Truncated Star Formation in Compact Groups of Galaxies: A Stellar Population Study

We present the results of a study comparing the stellar populations in theelliptical galaxies of Hickson Compact Groups (HCGs) with those in low densityenvironments. Three different population synthesis models and stellarpopulation analyses are used to make the results more robust. The low-sigmagalaxies in HCGs show an enhanced [Mg/Fe] ratio and a depleted metallicity[Z/H] with respect to their counterparts in the field. This behavior isinterpreted as evidence for the action of a mechanism which truncated the starformation (SF). Hydrodynamical simulations of galaxy mergers (Di Matteo et al.2005) support this interpretation by predicting the quenching of star formationsoon after the merger event. Combining this scenario and the evidence presentedhere, the HCGs, generally considered to be ideal environments for galaxy-galaxyinteractions, become ideal places for SF truncation.Comment: 18 pages, 9 figures. Accepted for publication in Astronomical Journa