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A new milky way halo star cluster in the southern galactic sky

Research output: Contribution to journalArticle

  • E. Balbinot
  • B. X. Santiago
  • L. da Costa
  • M. A. G. Maia
  • S. R. Majewski
  • D. Nidever
  • H. J. Rocha-Pinto
  • Professor Daniel Thomas
  • R. H. Wechsler
  • B. Yanny

We report on the discovery of a new Milky Way (MW) companion stellar system located at (αJ 2000, δJ 2000) = (22h10m43.s15, 1456_58.8). The discovery was made using the eighth data release of SDSS after applying an automated method to search for overdensities in the Baryon Oscillation Spectroscopic Survey footprint. Follow-up observations were performed using Canada–France–Hawaii Telescope/MegaCam, which reveal that this system is comprised of an old stellar population, located at a distance of 31.9+1.0−1.6 kpc, with a half-light radius of rh = 7.24+1.94−1.29 pc and a concentration parameter of c = log10(rt/rc) = 1.55. Asystematic isochrone fit to its color–magnitude diagram resulted in log (age yr−1) =10.07+0.05−0.03 and [Fe/H] = −1.58+0.08−0.13. These quantities are typical of globular clusters in the MW halo.The newly found object is of low stellar mass, whose observed excess relative to the background is caused by 95 ± 6 stars. The direct integration of its background decontaminated luminosity function leads to an absolute magnitude of MV = −1.21 ± 0.66. The resulting surface brightness is μV = 25.90 mag arcsec−2. Its position in the MV versus rh diagram lies close to AM4 and Koposov 1, which are identified as star clusters. The object is most likely a very faint star cluster—one of the faintest and lowest mass systems yet identified.

Original languageEnglish
Pages (from-to)101
JournalThe Astrophysical Journal
Issue number2
Early online date1 Apr 2013
Publication statusPublished - 20 Apr 2013

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