SIMBAD references

During the merger of two spiral galaxies powerful starbursts can be induced. By means of evolutionary spectral synthesis together with a 1-zone closed box model for the enrichment of individual chemical elements we investigate the evolution of the stellar population and the gas in the progenitor galaxies through starburst, merging, and beyond. In a parameter study we discuss the influence of the `Hubble types' (star formation histories) and ages of the progenitor spirals, and of the strength and duration of an interaction-induced starburst, on the optical to NIR colours, mass-to-light ratios, and chemical abundances of the merging system. The aim of this study is (i) to investigate under which circumstances and how rapidly merger remnants may evolve into the colour domain of E/S0 galaxies in different wavelength ranges, and (ii) to provide a grid of models for the interpretation of observed starburst systems and merger remnants. We find that strong as well as weak bursts during a merger in Sa through Sc type spirals, after 8 to 12 Gyr of undisturbed evolution, can leave a remnant with elliptical like colours at ∼15 Gyr, provided the burst duration is ∼10⁷ to 10⁸ yr. The late passive evolutionary reddening tracks are very similar for a wide variety of parameters. Thus, the observed narrow colour range of E/S0s does not prove a uniform single burst scenario for their formation, as emphasized also by Schweizer & Seitzer. Chemical abundances and element ratios in burst stars and possibly in part of the GC population might testify to a merger origin when many other signatures have already disappeared, and may, with accurate observations and modelling, help revealing and timing past merger events. Late mergers of gas rich (Sc, Sd) galaxies produce by far the largest portion of their burst stars when the metallicity of the ISM is slightly subsolar. Any globular clusters formed during such mergers should stand out as having metallicities higher than about 1/3 Z_☉ and abundance ratios typical of the ISM in the progenitor spirals. We discuss star formation efficiencies in massive spiral - spiral mergers and the conditions for a starburst to develop an IR - ultraluminous phase.