  We performed H-alpha imaging observations of 22 luminous infrared galaxies to
investigate how the distribution of star-forming regions in these galaxies is
related to galaxy interactions. Based on correlation diagrams between H-alpha
flux and continuum emission for individual galaxies, a sequence for the
distribution of star-forming regions was found: very compact (~100 pc) nuclear
starbursts with almost no star-forming activity in the outer regions (type 1),
dominant nuclear starbursts < 1 kpc in size and a negligible contribution from
the outer regions (type 2), nuclear starbursts > 1 kpc in size and a
significant contribution from the outer regions (type 3), and extended
starbursts with relatively faint nuclei (type 4). These classes of star-forming
region were found to be strongly related to global star-forming properties such
as star-formation efficiency, far-infrared color, and dust extinction. There
was a clear tendency for the objects with more compact distributions of
star-forming regions to show a higher star-formation efficiency and hotter
far-infrared color. An appreciable fraction of the sample objects were
dominated by extended starbursts (type 4), which is unexpected in the standard
scenario of interaction-induced starburst galaxies. We also found that the
distribution of star-forming regions was weakly but clearly related to galaxy
morphology: severely disturbed objects had a more concentrated distribution of
star-forming regions. This suggests that the properties of galaxy interactions,
such as dynamical phase and orbital parameters, play a more important role than
the internal properties of progenitor galaxies, such as dynamical structure or
gas mass fraction. We also discuss the evolution of the distribution of
star-forming regions in interacting galaxies.
