Luque, E;
Santiago, B;
Pieres, A;
Marshall, JL;
Pace, AB;
Kron, R;
Drlica-Wagner, A;
... Thomas, D; + view all
(2018)
Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey.
Monthly Notices of the Royal Astronomical Society
, 478
(2)
pp. 2006-2018.
10.1093/mnras/sty1039.
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Abstract
We report the discovery of a new star cluster, DES 3, in the constellation of Indus, and deeper observations of the previously identified satellite DES J0222.7-5217 (Eridanus III). DES 3 was detected as a stellar overdensity in first-year Dark Energy Survey data, and confirmed with deeper photometry from the 4.1-m Southern Astrophysical Research (SOAR) telescope. The new system was detected with a relatively high significance and appears in the DES images as a compact concentration of faint blue point sources. We determine that DES 3 is located at a heliocentric distance of ≃76.2 kpc and it is dominated by an old (≃9.8Gyr) and metal-poor ([Fe/H] ≃ -1.84) population. While the age and metallicity values of DES 3 are comparable to typical globular clusters (objects with a high stellar density, stellar mass of ~105 M⊙and luminosity MV~ -7.3), its half-light radius (rh~ 6.87 pc) and luminosity (MV~ -1.7) are more indicative of faint star cluster. Based on the angular size, DES 3, with a value of rh~ 0'.31, is among the smallest faint star clusters known to date. Furthermore, using deeper imaging of DES J0222.7-5217 taken with the SOAR telescope, we update structural parameters and perform the first isochrone modelling. Our analysis yields the first age (≃12.6Gyr) and metallicity ([Fe/H] ≃ -2.01) estimates for this object. The half-light radius (rh≃ 11.24 pc) and luminosity (MV≃ -2.4) of DES J0222.7-5217 suggest that it is likely a faint star cluster. The discovery of DES 3 indicates that the census of stellar systems in the MilkyWay is still far from complete, and demonstrates the power of modern wide-field imaging surveys to improve our knowledge of the Galaxy's satellite population.
| Type: | Article |
|---|---|
| Title: | Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/sty1039 |
| Publisher version: | http://dx.doi.org/10.1093/mnras/sty1039 |
| Language: | English |
| Additional information: | © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | globular clusters: general, Galaxy: halo |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10034338 |
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