The subgiant branch of ω Centauri seen through high-resolution spectroscopy: II. the most metal-rich population

E. Pancino, A. Mucciarelli, P. Bonifacio, L. Monaco, L. Sbordone

Resultado de la investigación: Article

14 Citas (Scopus)

Resumen

We analyze spectra of 18 stars belonging to the faintest subgiant branch in ω Centauri (the SGB-a), obtained with GIRAFFE@VLT at a resolution of R 17 000 and a S/N ratio between 25 and 50. We measure abundances of Al, Ba, Ca, Fe, Ni, Si, and Ti and we find that these stars have [Fe/H] =-0.73 ± 0.14 dex, similarly to the corresponding red giant branch population (the RGB-a). We also measure [α/Fe] = + 0.40 ± 0.16 dex, and [Ba/Fe] = + 0.87 ± 0.23 dex, in general agreement with past studies. It is very interesting to note that we found a uniform Al abundance, [Al/Fe] = + 0.32 ± 0.14 dex, for all the 18 SGB-a stars analysed here, thus supporting past evidence that the usual (anti-)correlations are not present in this population, and suggesting a non globular cluster-like origin of this particular population. In the dwarf galaxy hypothesis for the formation of ω Cen, this population might be the best candidate for the field population of its putative parent galaxy, although some of its properties appear contradictory. It has also been suggested that the most metal-rich population in ω Cen is significantly enriched in helium. If this is true, the traditional abundance analysis techniques, based on model atmospheres with normal helium content, might lead to errors. We have computed helium enhanced atmospheres for three stars in our sample and verified that the abundance errors due to the use of non-enhanced atmospheres are negligible. Additional, indirect support to the enhanced helium content of the SGB-a population comes from our Li upper limits.

Idioma originalEnglish
Número de artículoA53
PublicaciónAstronomy and Astrophysics
Volumen534
DOI
EstadoPublished - 11 oct 2011

Huella dactilar

helium
spectroscopy
high resolution
metal
metals
atmosphere
stars
atmospheres
dwarf galaxies
globular clusters
galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

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title = "The subgiant branch of ω Centauri seen through high-resolution spectroscopy: II. the most metal-rich population",
abstract = "We analyze spectra of 18 stars belonging to the faintest subgiant branch in ω Centauri (the SGB-a), obtained with GIRAFFE@VLT at a resolution of R 17 000 and a S/N ratio between 25 and 50. We measure abundances of Al, Ba, Ca, Fe, Ni, Si, and Ti and we find that these stars have [Fe/H] =-0.73 ± 0.14 dex, similarly to the corresponding red giant branch population (the RGB-a). We also measure [α/Fe] = + 0.40 ± 0.16 dex, and [Ba/Fe] = + 0.87 ± 0.23 dex, in general agreement with past studies. It is very interesting to note that we found a uniform Al abundance, [Al/Fe] = + 0.32 ± 0.14 dex, for all the 18 SGB-a stars analysed here, thus supporting past evidence that the usual (anti-)correlations are not present in this population, and suggesting a non globular cluster-like origin of this particular population. In the dwarf galaxy hypothesis for the formation of ω Cen, this population might be the best candidate for the field population of its putative parent galaxy, although some of its properties appear contradictory. It has also been suggested that the most metal-rich population in ω Cen is significantly enriched in helium. If this is true, the traditional abundance analysis techniques, based on model atmospheres with normal helium content, might lead to errors. We have computed helium enhanced atmospheres for three stars in our sample and verified that the abundance errors due to the use of non-enhanced atmospheres are negligible. Additional, indirect support to the enhanced helium content of the SGB-a population comes from our Li upper limits.",
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The subgiant branch of ω Centauri seen through high-resolution spectroscopy : II. the most metal-rich population. / Pancino, E.; Mucciarelli, A.; Bonifacio, P.; Monaco, L.; Sbordone, L.

En: Astronomy and Astrophysics, Vol. 534, A53, 11.10.2011.

Resultado de la investigación: Article

TY - JOUR

T1 - The subgiant branch of ω Centauri seen through high-resolution spectroscopy

T2 - II. the most metal-rich population

AU - Pancino, E.

AU - Mucciarelli, A.

AU - Bonifacio, P.

AU - Monaco, L.

AU - Sbordone, L.

PY - 2011/10/11

Y1 - 2011/10/11

N2 - We analyze spectra of 18 stars belonging to the faintest subgiant branch in ω Centauri (the SGB-a), obtained with GIRAFFE@VLT at a resolution of R 17 000 and a S/N ratio between 25 and 50. We measure abundances of Al, Ba, Ca, Fe, Ni, Si, and Ti and we find that these stars have [Fe/H] =-0.73 ± 0.14 dex, similarly to the corresponding red giant branch population (the RGB-a). We also measure [α/Fe] = + 0.40 ± 0.16 dex, and [Ba/Fe] = + 0.87 ± 0.23 dex, in general agreement with past studies. It is very interesting to note that we found a uniform Al abundance, [Al/Fe] = + 0.32 ± 0.14 dex, for all the 18 SGB-a stars analysed here, thus supporting past evidence that the usual (anti-)correlations are not present in this population, and suggesting a non globular cluster-like origin of this particular population. In the dwarf galaxy hypothesis for the formation of ω Cen, this population might be the best candidate for the field population of its putative parent galaxy, although some of its properties appear contradictory. It has also been suggested that the most metal-rich population in ω Cen is significantly enriched in helium. If this is true, the traditional abundance analysis techniques, based on model atmospheres with normal helium content, might lead to errors. We have computed helium enhanced atmospheres for three stars in our sample and verified that the abundance errors due to the use of non-enhanced atmospheres are negligible. Additional, indirect support to the enhanced helium content of the SGB-a population comes from our Li upper limits.

AB - We analyze spectra of 18 stars belonging to the faintest subgiant branch in ω Centauri (the SGB-a), obtained with GIRAFFE@VLT at a resolution of R 17 000 and a S/N ratio between 25 and 50. We measure abundances of Al, Ba, Ca, Fe, Ni, Si, and Ti and we find that these stars have [Fe/H] =-0.73 ± 0.14 dex, similarly to the corresponding red giant branch population (the RGB-a). We also measure [α/Fe] = + 0.40 ± 0.16 dex, and [Ba/Fe] = + 0.87 ± 0.23 dex, in general agreement with past studies. It is very interesting to note that we found a uniform Al abundance, [Al/Fe] = + 0.32 ± 0.14 dex, for all the 18 SGB-a stars analysed here, thus supporting past evidence that the usual (anti-)correlations are not present in this population, and suggesting a non globular cluster-like origin of this particular population. In the dwarf galaxy hypothesis for the formation of ω Cen, this population might be the best candidate for the field population of its putative parent galaxy, although some of its properties appear contradictory. It has also been suggested that the most metal-rich population in ω Cen is significantly enriched in helium. If this is true, the traditional abundance analysis techniques, based on model atmospheres with normal helium content, might lead to errors. We have computed helium enhanced atmospheres for three stars in our sample and verified that the abundance errors due to the use of non-enhanced atmospheres are negligible. Additional, indirect support to the enhanced helium content of the SGB-a population comes from our Li upper limits.

KW - Globular clusters: individual:ωCentauri

KW - Stars: abundances

UR - http://www.scopus.com/inward/record.url?scp=80053520383&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/201117378

DO - 10.1051/0004-6361/201117378

M3 - Article

AN - SCOPUS:80053520383

VL - 534

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

M1 - A53

ER -