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The role of E+A and post-starburst galaxies – I. Models and model results
Authors:M. A. Falkenberg  R. Kotulla   U. Fritze
Affiliation:Institut für Astrophysik Göttingen (IAG), Georg-August Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany;Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB
Abstract:Different compositions of galaxy types in the field in comparison to galaxy clusters as described by the morphology–density relation in the local universe are interpreted as a result of transformation processes from late- to early-type galaxies. This interpretation is supported by the Butcher–Oemler effect. We investigate E+A galaxies as an intermediate state between late-type galaxies in low-density environments and early-type galaxies in high-density environment to constrain the possible transformation processes. For this purpose, we model a grid of post-starburst galaxies by inducing a burst and/or a halting of star formation on the normal evolution of spiral galaxies with our galaxy evolution code galev . From our models, we find that the common E+A criteria exclude a significant number of post-starburst galaxies, and propose that comparing their spectral energy distributions leads to a more sufficient method to investigate post-starburst galaxies. We predict that a higher number of E+A galaxies in the early universe cannot be ascribed solely to a higher number of starburst, but is a result of a lower metallicity and a higher burst strength due to more gas content of the galaxies in the early universe. We find that even galaxies with a normal evolution without a starburst have an Hδ-strong phase at early galaxy ages.
Keywords:galaxies: clusters: general    galaxies: evolution    galaxies: formation    galaxies: interactions    galaxies: starburst
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