Chemically consistent evolution of galaxies

The composite stellar populations of galaxies comprise stars of a wide range of metallicities. Subsolar metallicities become increasingly important, both in the local universe when going from early towards later galaxy types as well as for dwarf galaxies and for all types of galaxies towards higher redshifts. We present a new generation of chemically consistent evolutionary synthesis models for galaxies of various spectral types from E through Sd. The models follow the chemical enrichment of the ISM and take into account the increasing initial metallicity of successive stellar generations using recently published metallicity dependent stellar evolutionary isochrones, spectra and yields. Our first set of closed-box 1-zone models does not include any spatial resolution or dynamics. For a Salpeter initial mass function (IMF) the star formation rate (SFR) and its time evolution are shown to successfully parameterise spectral galaxy types E, ..., Sd. We show how the stellar metallicity distribution in various galaxy types build up with time to yield after ~12 Gyr agreement with stellar metallicity distributions observed in our and other local galaxies. The models give integrated galaxy spectra over a wide wavelength range (90.9 Å–160 μm), which for ages of ~12 Gyr are in good agreement not only with observed broad band colours but also with template spectra for the respective galaxy types. Using filter functions for Johnson-Cousins $U,~B,~V,~{R_{\rm C}}$, IC, as well as for HST broad band filters in the optical and Bessel & Brett's NIR J, H, K filter system, we calculate the luminosity and colour evolution of model galaxies over a Hubble time. Including a standard cosmological model (${H_0 = 65, ~\Omega_0 = 0.1}$) and the attenuation by intergalactic hydrogen we present evolutionary and cosmological corrections as well as apparent luminosities in various filters over the redshift range from $z \sim 5$ to the present for our galaxy types and compare to earlier models using single (=solar) metallicity input physics only. We also resent a first comparison of our cc models to HDF data. A more detailed comparison with Hubble Deep Field (HDF) and other deep field data and an analysis and interpretation of high redshift galaxies in terms of ages, metallicities, star formation histories and, galaxy types will be the subject of a forthcoming paper