Ulrich Lindner

On the Nature and Redshift Evolution of DLA Galaxies

We extend our spiral galaxy models, which successfully describe nearby template spectra as well as the redshift evolution of CFRS and HDF spirals, to include – in a chemically consistent way – the redshift evolution of a series of individual elements. Comparison with observed DLA abundances shows that DLAs might well be the progenitors of present-day spiral types Sa through Sd. Our models bridge the gap between high redshift DLA and nearby spiral HII region abundances. The slow redshift evolution of DLA abundances is a natural consequence of the long SF timescales for discs, the scatter at any redshift reflects the range of SF timescales from early to late spiral types. We claim that, while at high redshift all spiral progenitor types seem to give rise to DLA absorption, towards low redshifts, the early-type spirals seem to drop out of DLA samples due to low gas and/or high metal and dust content. Model implications for the spectrophotometric properties of the DLA galaxy population are discussed in the context of campaigns for the optical identifications of DLA galaxies both at low and high redshift.

Chemical evolution of spiral galaxies from redshift 4 to the present

We use our unified chemical and spectrophotometric evolutionary synthesis code to describe galaxies of various Hubble types. With stellar evolutionary tracks and element yields for 5 different metallicities we follow the spectrophotometric evolution of composite stellar populations and the chemical evolution of ISM abundances in a chemically consistent way, i.e., accounting for the increasing initial metallicities of successive generations of stars. Evolutionary galaxy models are required to give agreement with template nearby galaxies of various Hubble types in terms of SEDs, stellar absorption indices or HII region abundances, respectively. Within the framework of a given cosmological model the redshift evolution of ISM abundances and abundance ratios is compared to damped Lyman

Predicting Spectral Properties of DLA Galaxies

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Interpreting the Redshift Evolution of DLA Galaxies

abundances. This provides information about the early star formation and nucleosynthesis history of the absorber galaxies and, at the same time, our models predict their spectral energy distributions. Optically identified DLA absorbers, with their spectral and chemical properties, provide, of course, the strongest constraints for the model parameters.

Void Hierarchy — a Guiding Principle to the Study of Faint Structures in Voids

Comparison of our chemically consistent models for spiral galaxies with observed DLA abundances shows that at high redshift DLA galaxies may well be the progenitors of normal spiral disks of all types from Sa through Sd. Towards lower redshifts z ≤ 1.5 however, early type spirals drop out of DLA samples due to low gas or/and high dust content. We use the spectrophotometric aspects of our unified spectral, chemical, and cosmological evolution models to predict expected luminosities in different bands for DLA galaxies at various redshifts and compare to the few optical identifications available.

Implications for Optical Identifications of QSO Absorption Systems from Galaxy Evolution Models

We interpret the redshift evolution of damped Lyman alpha galaxies with our new chemically consistent spectrophotometric evolution model.

THE DISTRIBUTION OF GALAXIES IN VOIDS

We introduce Void Hierarchy as an important property of the Large—Scale Structure in the Universe and demonstrate how it can be used to interpret observations. Moreover the void hierarchy constraints any realistic galaxy and structure formation scenario.

CHEMICALLY CONSISTENT EVOLUTION OF GALAXIES: SPIRAL GALAXY MODELS COMPAREDTO DLA SYSTEMS

We have made an attempt to compile all currently available data on optically identified QSO absorber systems (Lindner et al. 1996) to establish the status quo of absorber galaxy data as a basis for the investigation of galaxy evolution. We present a first comparison with results from our galaxy evolutionary synthesis models to demonstrate the potential power of this kind of approach and to guide future observations to identify absorber galaxies.