  ABRIDGED: A detailed 2D study of the central region of NGC5253 has been
performed to characterize the stellar and ionized gas structure as well as the
extinction distribution, physical properties and kinematics of the ionized gas
in the central ~210pc x 130pc. We utilized optical integral field spectroscopy
(IFS) data obtained with FLAMES. A detailed extinction map for the ionized gas
in NGC5253 shows that the largest extinction is associated with the prominent
Giant HII region. There is an offset of ~0.5" between the peak of the optical
continuum and the extinction peak in agreement with findings in the infrared.
We found that stars suffer less extinction than gas by a factor of 0.33. The
[SII]l6717/[SII]l6731 map shows an electron density (N_e) gradient declining
from the peak of emission in Ha (790cm^-3) outwards, while the argon line ratio
traces areas with $N_e~4200 - 6200cm^(-3). The area polluted with extra
nitrogen, as deduced from the excess [NII]/Ha, extends up to distances of 3.3"
(~60pc) from the maximum pollution, which is offset by ~1.5" from the peak of
continuum emission. Wolf-Rayet features are distributed in an irregular pattern
over a larger area (~100pc x 100pc) and associated with young stellar clusters.
We measured He^+ abundances over most of the field of view and values of
He^++/H^+<~0.0005 in localized areas which do not coincide, in general, with
the areas presenting W-R emission or extra nitrogen. The line profiles are
complex. Up to three emission components were needed to reproduce them. One of
them, associated with the giant HII region, presents supersonic widths and
[NII] and [SII] emission lines shifted up to 40km/s with respect to Ha.
Similarly, one of the narrow components presents offsets in the [NII] line of
<~20km/s. This is the first time that maps with such velocity offsets for a
starburst galaxy have been presented.
