Testing the Hierarchical Scenario with Field Disk Galaxy Evolution

We have constructed a data set of >250 field disk galaxies at redshifts 0.1 < z < 1.0 with Very Large Telescope (VLT) spectroscopy and Hubble Space Telescope imaging. This is one of the largest kinematical samples of distant disks to date. We use spatially resolved rotation curves to derive maximum rotation velocities and total masses; we also investigate disk sizes, bulge-to-disk ratios, stellar population properties etc. The stellar-to-total-mass ratios are constant over the probed cosmic epoch, which favors a hierarchical buildup of the dark matter halos the disks reside in. On the other hand, the mean stellar mass-to-light ratios evolve more strongly in the low-mass galaxies than in high-mass galaxies and the mean stellar ages are lower for low-mass galaxies than for high-mass galaxies. This points to an anti-hierarchical evolution of the stellar populations (aka "downsizing").