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Title: Spectroscopic study of extended star clusters in dwarf galaxy NGC 6822

We present a spectroscopic study of the four extended star clusters (ESCs) in NGC 6822 based on the data obtained with the Gemini Multi-Object Spectrograph on the Gemini-South 8.1 m telescope. The radial velocities derived from the spectra range from –61.2 ± 20.4 km s{sup –1} (for C1) to –115.34 ± 57.9 km s{sup –1} (for C4) and, unlike the intermediate-age carbon stars, they do not display any sign of systematic rotation around NGC 6822. The ages and metallicities derived using the Lick indices show that the ESCs are old (≥8 Gyr) and metal poor ([Fe/H] ≲ –1.5). NGC 6822 is found to have both metal poor ([Fe/H] ≈–2.0) and metal rich ([Fe/H] ≈–0.9) star clusters within 15' (2 kpc) from the center, whereas only metal poor clusters are observed in the outer halo with r ≥ 20'(2.6 kpc). The kinematics, old ages, and low metallicities of ESCs suggest that ESCs may have accreted into the halo of NGC 6822. Based on the velocity distribution of ESCs, we have determined the total mass and the mass-to-light ratio of NGC 6822: M{sub N6822}=7.5{sub −0.1}{sup +4.5}×10{sup 9} M{sub ⊙} and (M/L){sub N6822}=75{sub −1}{sup +45}(M/L){sub ⊙}. It shows that NGC 6822 is onemore » of the most dark matter dominated dwarf galaxies in the Local Group.« less
Authors:
;  [1] ; ; ;  [2] ; ;  [3] ;  [4]
  1. Korea Astronomy and Space Science Institute, 776 Daedeokdae-Ro Yuseong-Gu, Daejeon 305-348 (Korea, Republic of)
  2. Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)
  3. Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States)
  4. Gemini Observatory, Casilla 603, La Serena (Chile)
Publication Date:
OSTI Identifier:
22351350
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 783; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON STARS; DISTRIBUTION; GALAXIES; MASS; METALLICITY; NONLUMINOUS MATTER; RADIAL VELOCITY; ROTATION; SPECTRA; STAR CLUSTERS; TELESCOPES; VISIBLE RADIATION