THE KAPTEYN MOVING GROUP IS NOT TIDAL DEBRIS FROM ω CENTAURI

Journal Article · Mon Jul 20 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/808/1/103· OSTI ID:22522128

Navarrete, Camila; Chanamé, Julio ^[1]; Ramírez, Iván ^[2]; Meza, Andrés ^[3]; Anglada-Escudé, Guillem ^[4]; Shkolnik, Evgenya ^[5]

---

1. Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago (Chile)
2. Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1402, Austin, TX 78712-1206 (United States)
3. Departamento de Ciencias Fisicas, Universidad Andres Bello, Av. República 220, Santiago (Chile)
4. Astronomy Unit, School of Physics and Astronomy, Queen Mary, University of London, London E1 4NS (United Kingdom)
5. Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, AZ (United States)

The Kapteyn moving group has been postulated as tidal debris from ω Centauri. If true, members of the group should show some of the chemical abundance patterns known for stars in the cluster. We present an optical and near-infrared high-resolution, high-signal-to-noise ratio spectroscopic study of 14 stars of the Kapteyn group, plus 10 additional stars (the ω Cen group) that, while not listed as members of the Kapteyn group as originally defined, have nevertheless been associated dynamically with ω Centauri. Abundances for Na, O, Mg, Al, Ca, and Ba were derived from the optical spectra, while the strength of the chromospheric He i 10830 Å line is studied as a possible helium abundance indicator. The resulting Na–O and Mg–Al patterns for stars of the combined Kapteyn and ω Cen group samples do not resemble those of ω Centauri, and are not different from those of field stars of the Galactic halo. The distribution of equivalent widths of the He i 10830 Å line is consistent with that found among non-active field stars. Therefore, no evidence is found for second-generation stars within our samples, which most likely rules out a globular-cluster origin. Moreover, no hint of the unique barium overabundance at the metal-rich end, well established for ω Centauri stars, is seen among stars of the combined samples. Because this specific Ba pattern is present in ω Centauri irrespective of stellar generation, this would rule out the possibility that our entire sample might be composed of only first-generation stars from the cluster. Finally, for the stars of the Kapteyn group, the possibility of an origin in the hypothetical parent galaxy of ω Centauri is disfavored by the different run of α-elements with metallicity between our targets and stars from present-day dwarf galaxies.

• OSTI ID: 22522128
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 808; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ALUMINIUM
BARIUM
ELEMENT ABUNDANCE
HELIUM
MAGNESIUM
METALLICITY
MILKY WAY
ORIGIN
OXYGEN
RESOLUTION
SIGNAL-TO-NOISE RATIO
SODIUM
STAR CLUSTERS
STARS
STELLAR CHROMOSPHERES