Gas dynamics and star formation in the galaxy pair NGC 1512/1510☆

Here we present H i line and 20-cm radio continuum data of the nearby galaxy pair NGC 1512/1510 as obtained with the Australia Telescope Compact Array (ATCA). These are complemented by GALEX (Galaxy Evolution Explorer) ultraviolet (UV)-, SINGG H alpha- and Spitzer mid-infrared images, allowing us to compare the distribution and kinematics of the neutral atomic gas with the locations and ages of the stellar clusters within the system. For the barred, double-ring galaxy NGC 1512 we find a very large H i disc, similar to four times its optical diameter, with two pronounced spiral/tidal arms. Both its gas distribution and the distribution of the star-forming regions are affected by gravitational interaction with the neighbouring blue compact dwarf galaxy NGC 1510. While the inner disc of NGC 1512 shows quite regular rotation, deviations are visible along the outer arms and at the position of NGC 1510. From the H i rotation curve of NGC 1512 we estimate a dynamical mass of M(dyn) greater than or similar to 3 x 1011 M(circle dot), compared to an H i mass of M(H i) = 5.7 x 109 M(circle dot) (similar to 2 per cent M(dyn)). The two most distant H i clumps, at radii of similar to 80 kpc, show signs of star formation (SF) and are likely tidal dwarf galaxies (TDGs). Both lie along an extrapolation of the eastern-most H i arm, with the most compact H i cloud located at the tip of the arm. The 20-cm radio continuum map indicates extended SF activity not only in the central regions of both galaxies but also in between them. SF in the outer disc of NGC 1512 is revealed by deep optical- and two-colour UV images. Using the latter we determine the properties of greater than or similar to 200 stellar clusters and explore their correlation with dense H i clumps in the even larger 2X-H i disc. Outside the inner star-forming ring of NGC 1512, which must contain a large reservoir of molecular gas, H i turns out to be an excellent tracer of SF activity. The multiwavelength analysis of the NGC 1512/1510 system, which is probably in the first stages of a minor merger having started similar to 400 Myr ago, links stellar and gaseous galaxy properties on scales from 1 to 100 kpc.