A weak lensing estimate from GEMS of the virial to stellar mass ratio in massive galaxies to z~0.8
Abstract
We present constraints on the evolution of the virial to stellar mass ratio of galaxies with high stellar masses in the redshift range 0.2<z<0.8, by comparing weak lensing measurements of virial mass Mvir to estimates of stellar mass Mstar from COMBO-17. For a complete sample of galaxies with log(Mstar/ M) > 10.5, where the majority show an early-type morphology, we find that the virial mass to stellar mass ratio is given by Mvir/Mstar = 53+13-16. Assuming a baryon fraction from the concordance cosmology, this corresponds to a stellar fraction of baryons in massive galaxies of Omegab*/b = 0.10 +/- 0.03. Analysing the galaxy sample in different redshift slices, we find little or no evolution in the virial to stellar mass ratio, and place an upper limit of ~2.5 on the growth of massive galaxies through the conversion of gas into stars from z=0.8 to the present day.
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