Star Formation in CALIFA survey perturbed galaxies. II. Star Formation
  Histories and Oxygen Abundances
  Galaxy evolution is generally affected by tidal interactions. Firstly, in
this series, we reported several effects which suggest that tidal interactions
contribute to regulating star formation (SF). To confirm that so, we now
compare stellar mass assembly histories and SF look-back time annular profiles
between CALIFA survey tidally and non-tidally perturbed galaxies. We pair their
respective star-forming regions at the closest stellar mass surface densities
to reduce the influence of stellar mass. The assembly histories and annular
profiles show statistically significant differences so that higher star
formation rates characterize regions in tidally perturbed galaxies. These
regions underwent a more intense (re)activation of SF in the last 1 Gyr.
Varying shapes of the annular profiles also reflect fluctuations between
suppression and (re)activation of SF. Since gas-phase abundances use to be
lower in more actively than in less actively star-forming galaxies, we further
explore the plausible presence of metal-poor gas inflows able to dilute such
abundances. The resolved relations of oxygen (O) abundance, with stellar mass
density and with total gas fraction, show slightly lower O abundances for
regions in tidally perturbed galaxies. The single distributions of O abundances
statistically validate that so. Moreover, from a metallicity model based on
stellar feedback, the mass rate differentials (inflows$-$outflows) show
statistically valid higher values for regions in tidally perturbed galaxies.
These differentials, and the metal fractions from the population synthesis,
suggest dominant gas inflows in these galaxies. This dominance, and the
differences in SF through time, confirm the previously reported effects of
tidal interactions on SF.
