FSR 584 - a new globular cluster in the Galaxy?
Abstract
Aims:We investigate the nature of the recently catalogued star cluster candidate FSR 584, which is projected in the direction of the molecular cloud W 3 and may be the nearest globular cluster to the Sun.
Methods: 2MASS colour-magnitude diagrams, the stellar radial density profile, and proper motions are employed to derive fundamental and structural parameters.
Results: The colour-magnitude diagram morphology and the radial density profile show that FSR 584 is an old star cluster. With proper motions, the properties of FSR 584 are consistent with a metal-poor ([Fe/H]≈-2) globular cluster with a well-defined turnoff and evidence of a blue horizontal-branch. FSR 584 might be a Palomar-like halo globular cluster that is moving towards the Galactic plane, currently at ≈20 pc above it. The distance from the Sun is d_⊙≈1.4 kpc, and it is located at ≈1 kpc outside the Solar circle. The radial density profile is characterized by a core radius of R_core=0.3±0.1 pc. However, we cannot exclude the possibility of an old open cluster.
Conclusions: Near-infrared photometry coupled to proper motions support the scenario where FSR 584 is a new globular cluster in the Galaxy. The absorption is A_V=9.2±0.6, which makes it a limiting object in the optical and explains why it has so far been overlooked.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- September 2007
- DOI:
- 10.1051/0004-6361:20078029
- arXiv:
- arXiv:0709.3315
- Bibcode:
- 2007A&A...472..483B
- Keywords:
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- Galaxy: globular clusters: individual: FSR 584;
- Astrophysics
- E-Print:
- Astronomy and Astrophysics, accepted. 6 pages and 6 figures