Ionized gas outflows and global kinematics of low-z luminous star-forming galaxies

We study the kinematic properties of the ionised gas outflows and ambient interstellar medium (ISM) in a large and representative sample of local luminous and ultra-luminous infrared galaxies (U/LIRGs) (58 systems, 75 galaxies) at galactic and sub-galactic (i.e., star-forming clumps) scales, thanks to integral field spectroscopy (IFS)-based high signal-to-noise integrated spectra. The velocity dispersion of the ionized ISM in U/LIRGs ( similar to 70 km s(-1)) is larger than in lower luminosity local star-forming galaxies () similar to 25 km s(-l)). While for isolated disc LIRGs star formation appears to sustain turbulence, gravitational energy release associated with interactions and mergers plays an important role in driving sigma in the U/LIRG range. We find that sigma has a dependency on the star formation rate density (Sigma(SFR)), which is weaker than expected if it were driven by the energy released by the starburst. The relatively small role of star formation (SF) driving the cr in U/LIRGs is reinforced by the lack of an increase in sigma associated with high luminosity SF clumps. We also find that the impact of an active galactic nucleus (AGN) in ULIRGs is strong, increasing on average sigma by a factor 1.5. Low-z U/LIRGs cover a range of velocity dispersion (sigma similar to 30 to 100 km s(-1)) and star formation rate density (Sigma(SFR) similar to 0.1 to 20 M-circle dot yr(-1) kpc(-2)) similar to those of high-z SFGs. Moreover, the observed weak dependency of sigma on Sigma(SFR) for local U/LIRGs (sigma proportional to Sigma(+0.06)(SFR)) is in very good agreement with that measured in some high-z samples. The presence of ionized gas outflows in U/LIRGs seems universal based on the detection of a broad, usually blueshifted, H alpha line. The observed dependency of the maximum velocity of the outflow (V-max) on the star formation rate (SFR) is of the type V-max(non-AGN) proportional to SFR(L-IR)(+0.24). We find that AGNs in U/LIRGs are able to generate faster (similar to x2) and more massive (similar to x1.4) ionized gas outflows than pure starbursts. The derived ionized mass loading factors (eta) are in general below 1, with only a few AGNs above this limit. The escaping gas fraction is low with only less massive (log(M-dyn/M-circle dot) < 10.4) U/LIRGs having outflowing terminal velocities higher than their escape velocities, and more massive galaxies retaining the gas, even if they host an AGN. The observed average outflow properties in U/LIRGs are similar to high-z galaxies of comparable SFR. However, while high-z galaxies seem to require Sigma(SFR) > 1 M-circle dot yr(-1) kpc(-2) for launching strong outflows, this threshold is not observed in low-z U/LIRGs even after correcting for the differential fraction of the gas content. In the bright SF clumps found in LIRGs, ionized gas outflows appear to be very common (detection rate over 80%). Their observed properties are less extreme than those associated with the entire galaxy. The clumps in LIRGs follow the general size-L-sigma scaling relations found for low- and high-z clumps, though they are in general smaller, less luminous, and are characterized by lower sigma than at high-z. For a given observed (no internal extinction correction applied) star formation surface density, outflows in LIRG clumps would be about one to two orders of magnitude less energetic than the outflows launched by clumps in high-z SF galaxies.