The Evolution of Field Spiral Galaxies over the Past 8 Gyr

We have performed a large observing campaign of intermediate-redshift disk galaxies including spectroscopy with the FORS instruments of the VLT and imaging with the Advanced Camera for Surveys onboard the HST. Our data set comprises 113 late-type galaxies in the redshift range 0.1<z<1.0 and thereby probes galaxy evolution over more than half the age of the universe. Spatially resolved rotation curves have been extracted and fitted with synthetic velocity fields that account for geometric distortions and blurring effects. With these models, the intrinsic maximum rotation velocity Vmax was derived for 73 spirals. By comparing our sample to the Tully-Fisher Relation of local spiral galaxies, we find evidence for a differential luminosity evolution: the massive distant galaxies are of comparable luminosity as their present-day counterparts, while the distant low-mass spirals are brighter than locally by up to >2mag in rest-frame B. This evolution would be at variance with the predictions from numerical simulations. On the other hand, the disks of the distant galaxies are, for a given Vmax, slightly smaller than those of their local counterparts, as expected for a hierarchical structure growth. Hence, the discrepancy between the observations and theoretical predictions would be limited to the properties of the stellar populations. A possible explanation could be the suppression of star formation in low-mass disks which is not yet properly implemented in models of galaxy evolution. (abridged)