Lower metallicity limit of the galactic globular cluster system: Calcium triplet spectroscopy of metal-poor globular cluster giants

Doug Geisler, Andrés E. Piatti, Juan J. Clariá, Dante Minniti

Resultado de la investigación: Article

49 Citas (Scopus)

Resumen

Medium-resolution spectra at the Ca II infrared triplet are presented for 164 giants in 12 metal-poor Galactic globular clusters. The data for 4 of these clusters are combined with published data for 7 other clusters with well-known metal abundances and used to calibrate the derivation of metallicity values for the remaining clusters from the summed strength of the 2 strongest Ca lines at a given V - VHB. The mean [Fe/H] values we find are: -1.82 for NGC 2298, -2.10 for NGC 4372, -1.84 for NGC 4833, -2.10 for NGC 5053, -1.87 for NGC 5694, -1.94 for NGC 5897, -1.86 for NGC 6101 and -1.86 for NGC 6144, with a typical mean error of 0.05 dex from an average of 10 member giants per cluster. Upper limits to any intrinsic intracluster metallicity dispersion are ≤0.05 dex in all of the clusters except ∼0.15 dex in NGC 5053 and NGC 5694, where the higher limits are due to the lower quality spectra for these more distant clusters. The mean metallicity values for most of the program clusters are in excellent agreement with the Zinn [ApJ, 293, 424 (1985)] scale, while those for NGC 5897 and NGC 5053 are 0.26 dex lower and 0.48 dex higher than given by Zinn, respectively. The value for NGC 5897 is intermediate to that given by the Washington photometry of Geisler et al. [AJ, 104, 627 (1992b)] and Zinn. The high value for NGC 5053 increases the already very significant difference between the metallicity distribution functions of halo clusters and field stars. Our results, combined with previous determinations for other clusters, indicate that the lower metallicity limit for globular clusters in the Galaxy is -2.25±0.10. A similar value also appears to hold for other nearby globular cluster systems. We also derive mean cluster radial velocities to a typical precision of 1.2 km/s (mean error). The values for several of the program clusters are significantly different from previously published values. An updated analysis slightly strengthens van den Bergh's [AJ, 105, 971 (1993)] finding that halo clusters on retrograde orbits have different horizontal branch morphologies than clusters on prograde orbits.

Idioma originalEnglish
Páginas (desde-hasta)605-617
Número de páginas13
PublicaciónAstronomical Journal
Volumen109
N.º2
EstadoPublished - 1 feb 1995

Huella dactilar

globular clusters
metallicity
calcium
spectroscopy
metal
den
metals
programme
halos
retrograde orbits
star distribution
star clusters
trucks
radial velocity
photometry
distribution
analysis
derivation
distribution functions
galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

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title = "Lower metallicity limit of the galactic globular cluster system: Calcium triplet spectroscopy of metal-poor globular cluster giants",
abstract = "Medium-resolution spectra at the Ca II infrared triplet are presented for 164 giants in 12 metal-poor Galactic globular clusters. The data for 4 of these clusters are combined with published data for 7 other clusters with well-known metal abundances and used to calibrate the derivation of metallicity values for the remaining clusters from the summed strength of the 2 strongest Ca lines at a given V - VHB. The mean [Fe/H] values we find are: -1.82 for NGC 2298, -2.10 for NGC 4372, -1.84 for NGC 4833, -2.10 for NGC 5053, -1.87 for NGC 5694, -1.94 for NGC 5897, -1.86 for NGC 6101 and -1.86 for NGC 6144, with a typical mean error of 0.05 dex from an average of 10 member giants per cluster. Upper limits to any intrinsic intracluster metallicity dispersion are ≤0.05 dex in all of the clusters except ∼0.15 dex in NGC 5053 and NGC 5694, where the higher limits are due to the lower quality spectra for these more distant clusters. The mean metallicity values for most of the program clusters are in excellent agreement with the Zinn [ApJ, 293, 424 (1985)] scale, while those for NGC 5897 and NGC 5053 are 0.26 dex lower and 0.48 dex higher than given by Zinn, respectively. The value for NGC 5897 is intermediate to that given by the Washington photometry of Geisler et al. [AJ, 104, 627 (1992b)] and Zinn. The high value for NGC 5053 increases the already very significant difference between the metallicity distribution functions of halo clusters and field stars. Our results, combined with previous determinations for other clusters, indicate that the lower metallicity limit for globular clusters in the Galaxy is -2.25±0.10. A similar value also appears to hold for other nearby globular cluster systems. We also derive mean cluster radial velocities to a typical precision of 1.2 km/s (mean error). The values for several of the program clusters are significantly different from previously published values. An updated analysis slightly strengthens van den Bergh's [AJ, 105, 971 (1993)] finding that halo clusters on retrograde orbits have different horizontal branch morphologies than clusters on prograde orbits.",
author = "Doug Geisler and Piatti, {Andr{\'e}s E.} and Clari{\'a}, {Juan J.} and Dante Minniti",
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Lower metallicity limit of the galactic globular cluster system : Calcium triplet spectroscopy of metal-poor globular cluster giants. / Geisler, Doug; Piatti, Andrés E.; Clariá, Juan J.; Minniti, Dante.

En: Astronomical Journal, Vol. 109, N.º 2, 01.02.1995, p. 605-617.

Resultado de la investigación: Article

TY - JOUR

T1 - Lower metallicity limit of the galactic globular cluster system

T2 - Calcium triplet spectroscopy of metal-poor globular cluster giants

AU - Geisler, Doug

AU - Piatti, Andrés E.

AU - Clariá, Juan J.

AU - Minniti, Dante

PY - 1995/2/1

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N2 - Medium-resolution spectra at the Ca II infrared triplet are presented for 164 giants in 12 metal-poor Galactic globular clusters. The data for 4 of these clusters are combined with published data for 7 other clusters with well-known metal abundances and used to calibrate the derivation of metallicity values for the remaining clusters from the summed strength of the 2 strongest Ca lines at a given V - VHB. The mean [Fe/H] values we find are: -1.82 for NGC 2298, -2.10 for NGC 4372, -1.84 for NGC 4833, -2.10 for NGC 5053, -1.87 for NGC 5694, -1.94 for NGC 5897, -1.86 for NGC 6101 and -1.86 for NGC 6144, with a typical mean error of 0.05 dex from an average of 10 member giants per cluster. Upper limits to any intrinsic intracluster metallicity dispersion are ≤0.05 dex in all of the clusters except ∼0.15 dex in NGC 5053 and NGC 5694, where the higher limits are due to the lower quality spectra for these more distant clusters. The mean metallicity values for most of the program clusters are in excellent agreement with the Zinn [ApJ, 293, 424 (1985)] scale, while those for NGC 5897 and NGC 5053 are 0.26 dex lower and 0.48 dex higher than given by Zinn, respectively. The value for NGC 5897 is intermediate to that given by the Washington photometry of Geisler et al. [AJ, 104, 627 (1992b)] and Zinn. The high value for NGC 5053 increases the already very significant difference between the metallicity distribution functions of halo clusters and field stars. Our results, combined with previous determinations for other clusters, indicate that the lower metallicity limit for globular clusters in the Galaxy is -2.25±0.10. A similar value also appears to hold for other nearby globular cluster systems. We also derive mean cluster radial velocities to a typical precision of 1.2 km/s (mean error). The values for several of the program clusters are significantly different from previously published values. An updated analysis slightly strengthens van den Bergh's [AJ, 105, 971 (1993)] finding that halo clusters on retrograde orbits have different horizontal branch morphologies than clusters on prograde orbits.

AB - Medium-resolution spectra at the Ca II infrared triplet are presented for 164 giants in 12 metal-poor Galactic globular clusters. The data for 4 of these clusters are combined with published data for 7 other clusters with well-known metal abundances and used to calibrate the derivation of metallicity values for the remaining clusters from the summed strength of the 2 strongest Ca lines at a given V - VHB. The mean [Fe/H] values we find are: -1.82 for NGC 2298, -2.10 for NGC 4372, -1.84 for NGC 4833, -2.10 for NGC 5053, -1.87 for NGC 5694, -1.94 for NGC 5897, -1.86 for NGC 6101 and -1.86 for NGC 6144, with a typical mean error of 0.05 dex from an average of 10 member giants per cluster. Upper limits to any intrinsic intracluster metallicity dispersion are ≤0.05 dex in all of the clusters except ∼0.15 dex in NGC 5053 and NGC 5694, where the higher limits are due to the lower quality spectra for these more distant clusters. The mean metallicity values for most of the program clusters are in excellent agreement with the Zinn [ApJ, 293, 424 (1985)] scale, while those for NGC 5897 and NGC 5053 are 0.26 dex lower and 0.48 dex higher than given by Zinn, respectively. The value for NGC 5897 is intermediate to that given by the Washington photometry of Geisler et al. [AJ, 104, 627 (1992b)] and Zinn. The high value for NGC 5053 increases the already very significant difference between the metallicity distribution functions of halo clusters and field stars. Our results, combined with previous determinations for other clusters, indicate that the lower metallicity limit for globular clusters in the Galaxy is -2.25±0.10. A similar value also appears to hold for other nearby globular cluster systems. We also derive mean cluster radial velocities to a typical precision of 1.2 km/s (mean error). The values for several of the program clusters are significantly different from previously published values. An updated analysis slightly strengthens van den Bergh's [AJ, 105, 971 (1993)] finding that halo clusters on retrograde orbits have different horizontal branch morphologies than clusters on prograde orbits.

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