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Based on magnitudes and Petrosian radii from the Sloan Digital Sky Survey(SDSS, data release 7) at low redhift (z <0.2), we developed a test ofgalaxy-size evolution. For this first quantitative size analysis using SDSSdata, several possible sources of systematic errors had to be considered. TheMalmquist bias is excluded by volume-limited samples. A correction for seeinghas been developed and applied. We compare different methods to perform theK-correction, and avoid selection effects due to different filters. It is foundthat apparent average galaxy size slightly decreases with redshift z,corresponding to a growth in time. The effect is smaller for a lower H0, and atthe same time less pronounced at higher redshifts, but persists in both cases.Although there is no systematic variation with galaxy luminosity, we took intoaccount the recently discovered luminosity evolution with redshift. Assumingthis effect of unknown origin to be real, we find a slight increase of galaxysize with z. The relative change of average size with z usually amounts to lessthan one half of the respective increase of wavelengths due to the cosmologicalredshift, making a cosmological interpretation difficult. While the effectshows clear statistical significance, unknown systematics cannot be excluded.In any case, the enigmatic observations of size and luminosity evolution needto be analysed together. To facilitate further investigations, a completeMathematica code and instructions for data download are provided.

Do Galaxies Change in Size ? An Angular Size Test at Low Redshift with SDSS Data