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 ( < \sigma > \sim 70 kms ^ { -1 } ) is larger than in lower luminosity local star-forming galaxies ( < \sigma > \sim 25 kms ^ { -1 } ) .
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 \sigma 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 \sim 30 to 100 km s { { } ^ { -1 } } ) and star formation rate density ( \Sigma _ { SFR } \sim 0.1 to 20 M _ { \odot } yr ^ { -1 } kpc ^ { -2 } ) similar to those of SFGs .
Moreover , the observed weak dependency of \sigma on \Sigma _ { SFR } for local U/LIRGs ( \sigma \propto \Sigma _ { SFR } ^ { +0.06 } ) 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 ) \propto SFR ( L _ { IR } ) ^ { +0.24 } .
We find that AGNs in U/LIRGs are able to generate faster ( \sim \times 2 ) and more massive ( \sim \times 1.4 ) 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 _ { \odot } ) < 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 _ { \odot } 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 .