NGC 2782: a merger remnant with young stars in its gaseous tidal tail

We have searched for young star-forming regions around the merger remnant NGC 2782. By using Galaxy Evolution Explorer far-ultraviolet and near-ultraviolet imaging and H I data we found seven ultraviolet sources, located at distances greater than 26 kpc from the centre of NGC 2782, and coinciding with its western H I tidal tail. These regions were resolved in several smaller systems when Gemini/Gemini multi-object spectrograph (GMOS) r-band images were used. We compared the observed colours to stellar population synthesis models and found that these objects have ages of ∼1 to 11 Myr and masses ranging from 10^3.9 to 10^4.6 M_⊙. By using Gemini/GMOS spectroscopic data we confirm memberships and derive high metallicities for three of the young regions in the tail (12+log(O/H) = 8.74 ± 0.20, 8.81 ± 0.20 and 8.78 ± 0.20). These metallicities are similar to the value presented by the nuclear region of NGC 2782 and also similar to the value presented for an object located close to the main body of NGC 2782. The high metallicities measured for the star-forming regions in the gaseous tidal tail of NGC 2782 could be explained if they were formed out of highly enriched gas which was once expelled from the centre of the merging galaxies when the system collided. An additional possibility is that the tail has been a nursery of a few generations of young stellar systems which ultimately polluted this medium with metals, further enriching the already pre-enriched gas ejected to the tail when the galaxies collided. ^a r-band magnitude inside a fixed aperture of 4 arcsec radius and corrected by MW extinction. Region 2 appears to have diffuse emission in the r-band image. ^b Fixed FUV-band magnitudes corrected by apertures (as described in Section 3.2) and MW extinction. ^c FUV-r colours. ^d Magnitudes were measured in a fixed aperture of 4 arcsec radius and corrected by MW extinction. FUV and NUV magnitudes were corrected by aperture, as described in Section 3.2. ^e Left values: E(B-V) estimated as in Section 3.3. Right values: E(B-V) estimated by using the H I data of NGC 2782. Total extinction is the sum of the internal and Galactic extinctions (0.13 mag in this band). ^f Ages estimated from FUV-NUV and FUV-r. In parenthesis we show the ages estimated from the Hβ equivaland SB99 models. ^g Distance from the centre of the galaxy, assuming a position angle and inclination of 0°.