A Quantitative Study of the Evolution of Faint Field Galaxies

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Session 30 -- Clusters of Galaxies
Display presentation, Tuesday, 9:30-6:30, Pauley Room

[30.02] A Quantitative Study of the Evolution of Faint Field Galaxies

C. Gronwall, D.C. Koo (UCSC)

Many workers have concluded that there is a significant excess of galaxy counts above standard non-evolutionary models. Recent redshift surveys, however, have shown that galaxies fainter than 20th mag have redshift distributions close to those predicted by non-evolutionary models. These results have led to the introduction of many exotic theories such as rapid merging, disappearing populations of dwarf galaxies, and the adoption of a cosmological constant. Using a new modeling technique, we found that a no-evolution model fits the observed optical and near-IR counts, $B-R$ colors, and redshifts of faint field galaxies surprising well. Thus we conclude that exotic forms of galaxy evolution are probably not needed to explain the observed data.

Our models differ from those of previous workers by not assuming that the local luminosity function is well defined. Instead, we use a non-negative least squares technique to determine, quantitatively and objectively, whether any set of luminosity functions for different spectral types of galaxies is compatible with the observed data. Using the most recent data sets combined with our new technique, we will present improved matches to the observations by including some color and luminosity evolution in the spectra of distant galaxies. We will also show the effects of the variation of cosmological parameters.

Tuesday program listing