Evidence for secular evolution of disc structural parameters in massive barred galaxies.

We address the effects of bar-driven secular evolution in discs by comparing their properties in a sample of nearly 700 unbarred and barred (42 ± 3 per cent of the population) massive disc galaxies (M_⋆ ≥ 10¹⁰ M_⊙). We make use of accurate structural parameters derived from i-band bulge/disc/bar decompositions to show that, as a population, barred discs tend to have fainter central surface brightness (Δμ₀ ≈ 0.25 mag), and disc scalelengths that are ≈15 per cent larger than those of unbarred galaxies of the same stellar mass. The corresponding distributions of μ₀ and h are statistically inconsistent at the 5.2σ and 3.8σ levels, respectively. Bars rarely occur in high-surface brightness discs, with less than 5 per cent of the barred population having μ₀ < 19.5 mag arcsec^-2 - compared to 20 per cent for unbarred galaxies. They tend to reside in moderately blue discs, with a bar fraction that peaks at (g - i)_disc ≈ 0.95 mag and mildly declines for both bluer and redder colours. These results demonstrate noticeable structural differences between the discs of barred and unbarred galaxies, which we argue are the result of bar-driven evolution - in qualitative agreement with longstanding theoretical expectations.