Age-dating the Tully-Fisher relation at moderate redshift
  We analyse the Tully-Fisher relation at moderate redshift from the point of
view of the underlying stellar populations, by comparing optical and NIR
photometry with a phenomenological model that combines population synthesis
with a simple prescription for chemical enrichment. The sample comprises 108
late-type galaxies extracted from the FORS Deep Field (FDF) and William
Herschel Deep Field (WHDF) surveys at z<1 (median redshift z=0.45). A
correlation is found between stellar mass and the parameters that describe the
star formation history, with massive galaxies forming their populations early
(zFOR~3), with star formation timescales, tau1~4Gyr; although with very
efficient chemical enrichment timescales (tau2~1Gyr). In contrast, the
stellar-to-dynamical mass ratio - which, in principle, would track the
efficiency of feedback in the baryonic processes driving galaxy formation -
does not appear to correlate with the model parameters. On the Tully-Fisher
plane, no significant age segregation is found at fixed circular speed, whereas
at fixed stellar-to-dynamical mass fraction, age splits the sample, with older
galaxies having faster circular speeds at fixed Ms/Mdyn. Although our model
does not introduce any prior constraint on dust reddening, we obtain a strong
correlation between colour excess and stellar mass.
