Journal Article

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

S. Torres‐Flores, C. Mendes de Oliveira, D. F. de Mello, S. Scarano and F. Urrutia‐Viscarra

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 421, issue 4, pages 3612-3621
Published in print April 2012 | ISSN: 0035-8711
Published online April 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.20589.x
NGC 2782: a merger remnant with young stars in its gaseous tidal tail*

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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 103.9 to 104.6 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.

Keywords: galaxies: interactions; intergalactic medium; galaxies: star clusters: general

Journal Article.  8033 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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