  LIRGs and ULIRGs are much more numerous at higher redshifts than locally,
dominating the star-formation rate density at redshifts ~1 - 2. Therefore, they
are important objects in order to understand how galaxies form and evolve
through cosmic time. We aim to characterize the morphologies of the stellar
continuum and the ionized gas (H_alpha) emissions from local sources, and
investigate how they relate with the dynamical status and IR-luminosity of the
sources. We use optical (5250 -- 7450 \AA) integral field spectroscopic (IFS)
data for a sample of 38 sources, taken with the VIMOS instrument, on the VLT.
We present an atlas of IFS images of continuum emission, H_alpha emission, and
H_alpha equivalent widths for the sample. The H_alpha images frequently reveal
extended structures that are not visible in the continuum, such as HII regions
in spiral arms, tidal tails, rings, of up to few kpc from the nuclear regions.
The morphologies of the continuum and H_alpha images are studied on the basis
of the C_{2kpc} parameter, which measures the concentration of the emission
within the central 2 kpc. The C_{2kpc} values found for the H_alpha images are
higher than those of the continuum for the majority (85%) of the objects in our
sample. On the other hand, most of the objects in our sample (~62%) have more
than half of their H_alpha emission outside the central 2 kpc. No clear trends
are found between the values of C_{2kpc} and the IR-luminosity of the sources.
On the other hand, our results suggest that the star formation in advance
mergers and early-stage interactions is more concentrated than in isolated
objects. We compared the H_alpha and infrared emissions as tracers of the
star-formation activity. We find that the star-formation rates derived using
the H_alpha luminosities generally underpredict those derived using the IR
luminosities, even after accounting for reddening effects.
