2015MNRAS.450.3381L

We present deep, intermediate-resolution, optical spectroscopy of 136 genuine UV-bright regions located in both the inner and outer regions of NGC 1512. This galaxy is in close interaction with the blue compact dwarf galaxy NGC 1510 and possesses two prominent HI arms where extended ultraviolet complexes are found. Our data were taken using 2dF/AAOmega at the 3.9 m Anglo-Australian Telescope and are combined with the HI data from Local Volume HI Survey and Galaxy Evolution Explorer UV data. We detect ionized gas in 82 percent of the complexes, many of them located between 1 and 6.6 R25. We found significant differences between regions along the Arm 1 - 8.25 ≲ 12+log(O/H) ≲ 8.45 -, and knots located in the external debris of Arm 2, -8.40 ≲ 12+log(O/H) ≲ 8.60-. Considering a radial and an azimuthal gradient following the HI arms, we confirm that Arm 2 has experienced an enhancement in star formation because of the interaction with NGC 1510 and flattened the radial metallicity at large radii. Arm 1 appears to retain the original and poorly disturbed radial distribution. We trace the kinematics of the system up to 78 kpc using the Hα emission, which matches well that provided by the HI. We estimate that the gas existing at large galactocentric radii had a metallicity of 12+log(O/H) ∼ 8.1 before the interaction started around 400 Myr ago. The metals within the HI gas are very likely not coming from the inner regions of NGC 1512 but probably from material accreted during minor mergers or outflow-enriched intergalactic medium gas during the life of the galaxy.