  The luminous infrared galaxy Arp299 (IC694+NGC3690) is studied using optical
integral field spectroscopy obtained with the INTEGRAL system, together with
archival Hubble Space Telescope WFPC2 and NICMOS images. The stellar and
ionized gas morphology shows lambda-dependent variations due to the combined
effects of the dust internal extinction, and the nature and spatial
distribution of the different ionizing sources. The two-dimensional ionization
maps have revealed an off-nuclear conical structure of about 4 kpc in length,
characterized by high excitation conditions and a radial gradient in the gas
electron density. The apex of this structure coincides with B1 region of
NGC3690 which, in turn, presents Seyfert-like ionization, high extinction and a
high velocity dispersion. These results strongly support the hypothesis that B1
is the true nucleus of NGC3690, where an AGN is located. In the circumnuclear
regions HII-like ionization dominates, while LINER-like ionization is found
elsewhere. The Halpha emitting sources with ages from 3.3 to 7.2x10^6 years,
have masses of between 6 and 680x10^6 Msun and contribute (extinction
corrected) about 45% to the bolometric luminosity. The ionized (Halpha) and
neutral (NaD) gas velocity fields show similar structure on scales of several
hundred to about 1 kpc, indicating that these gas components are kinematically
coupled. The kinematic structure is complex and on scales of about 0.2 kpc does
not appear to be dominated by the presence of ordered, rotational motions. The
large velocity dispersion measured in NGC3690 indicates that this galaxy is the
most massive of the system. The low velocity amplitude and dispersion of the
interface suggest that the ionized gas is slowly rotating or in a close to
quiescent phase.
