Galaxy evolution on resolved scales: ageing and quenching in CALIFA
  This work investigates the fundamental mechanism(s) that drive galaxy
evolution in the Local Universe. By comparing two proxies of star-formation
sensitive to different timescales, such as EW(H$\alpha$) and colours like
$g-r$, one may distinguish between smooth secular evolution (ageing) and sudden
changes (quenching) on the recent star formation history of galaxies. Building
upon the results obtained from a former study based on 80.000 SDSS single-fibre
measurements, we now focus on spatially-resolved (on kpc scales) galaxies,
comparing with a sample of 637 nearby objects observed by the CALIFA survey. In
general, galaxies cannot be characterised in terms of a single `evolutionary
stage'. Individual regions within galaxies arrange along a relatively narrow
ageing sequence, with some intrinsic scatter possibly due to their different
evolutionary paths. These sequences, though, differ from one galaxy to another,
although they are broadly consistent with the overall distribution found for
the (central) SDSS spectra. We find evidence of recent quenching episodes
(relatively blue colours and strong H$\alpha$ absorption) in a small fraction
of galaxies (most notably, low-mass ellipticals), on global scales and
individual regions (particularly at high metallicity). However, we argue that
most of the systems, over their entire extent, are compatible with a secular
inside-out scenario, where the evolutionary stage correlates with both global
(mass, morphology, and environment) as well as local (surface brightness and
metallicity) properties.
