Revealing the complexity of the dwarf merging system NGC 1487

Context. Interacting galaxies provide a natural place to study the star formation process under extreme conditions. In particular, the merger between dwarf galaxies can promote the formation of low-mass star-forming objects in tidal tails. These low-mass systems can be used to trace star formation and the metal content in the outskirts of merging systems. Aims. We analyzed the system NGC 1487, the result of the merging of dwarf galaxies, to determine the physical properties of 22 star-forming regions located in its tidal tails and 7 regions located in its central area. This analysis allowed us to quantify the oxygen abundances in the outskirts of a merger between dwarf galaxies, which is relevant in the context of gas metal mixing. Methods. We used Gemini/GMOS spectroscopic data and strong-line methods to determine the chemical abundances of sources located in the tidal tails of NGC 1487. We also determined ages by comparing the observed H α equivalent width to model values. For each region, we determined its ionization mechanism and extinctions using emission line fluxes. Results. We determined the ages for 22 regions located in the tidal tails of NGC 1487, which range from 2.3 Myr to 6.2 Myr. These regions show subsolar oxygen abundances and low-level star formation. Star-forming regions in the tidal tails of NGC 1487 have oxygen abundances similar to those measured for the central region, suggesting that gas mixing is taking place in NGC 1487. The main mechanism responsible for this gas-mixing process is the interaction between the merging galaxies, where less-enriched material is transported to the central region of the system. In the central region, the ages of the star-forming sources range from 2.8 ± 1.7 Myr to 4.6 ± 0.7 Myr. One of these sources displays Wolf-Rayet features, suggesting a very recent star formation process. The most intense star formation bursts occur in the nuclear region; however, the star formation proceeds at a modest level there. These results are consistent with previous findings that suggest that NGC 1487 is the merger of dwarf galaxies.