Galaxy And Mass Assembly (GAMA): the effect of close interactions on
  star formation in galaxies
  The modification of star formation (SF) in galaxy interactions is a complex
process, with SF observed to be both enhanced in major mergers and suppressed
in minor pair interactions. Such changes likely to arise on short timescales
and be directly related to the galaxy-galaxy interaction time. Here we
investigate the link between dynamical phase and direct measures of SF on
different timescales for pair galaxies, targeting numerous star-formation rate
(SFR) indicators and comparing to pair separation, individual galaxy mass and
pair mass ratio. We split our sample into the higher (primary) and lower
(secondary) mass galaxies in each pair and find that SF is indeed enhanced in
all primary galaxies but suppressed in secondaries of minor mergers. We find
that changes in SF of primaries is consistent in both major and minor mergers,
suggesting that SF in the more massive galaxy is agnostic to pair mass ratio.
We also find that SF is enhanced/suppressed more strongly for short-time
duration SFR indicators (e.g. H-alpha), highlighting recent changes to SF in
these galaxies, which are likely to be induced by the interaction. We propose a
scenario where the lower mass galaxy has its SF suppressed by gas heating or
stripping, while the higher mass galaxy has its SF enhanced, potentially by
tidal gas turbulence and shocks. This is consistent with the seemingly
contradictory observations for both SF suppression and enhancement in close
pairs.
