2009MNRAS.400.1749K

Here we present Hi line and 20-cm radio continuum data of the nearby galaxy pair NGC1512/1510 as obtained with the Australia Telescope Compact Array (ATCA). These are complemented by GALEX (Galaxy Evolution Explorer) ultraviolet (UV)-, SINGG Hα- 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 NGC1512 we find a very large Hi disc, ∼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 NGC1510. While the inner disc of NGC1512 shows quite regular rotation, deviations are visible along the outer arms and at the position of NGC1510. From the Hi rotation curve of NGC1512 we estimate a dynamical mass of M_dyn≳ 3x10¹¹M_☉, compared to an Hi mass of M_Hi= 5.7x10⁹M_☉(∼2 per cent M_dyn).

The two most distant Hi clumps, at radii of ∼80kpc, show signs of star formation (SF) and are likely tidal dwarf galaxies (TDGs). Both lie along an extrapolation of the eastern-most Hi arm, with the most compact Hi 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 NGC1512 is revealed by deep optical- and two-colour UV images. Using the latter we determine the properties of ≳200 stellar clusters and explore their correlation with dense Hi clumps in the even larger 2X-Hi disc. Outside the inner star-forming ring of NGC1512, which must contain a large reservoir of molecular gas, Hi turns out to be an excellent tracer of SF activity.

The multiwavelength analysis of the NGC1512/1510 system, which is probably in the first stages of a minor merger having started ∼400Myr ago, links stellar and gaseous galaxy properties on scales from 1 to 100kpc.