The metallicity extremes of the Sagittarius dSph: SALT spectroscopy of PNe

Alexei Y. Kniazev, Albert A. Zijlstra, Eva K. Grebel, Leonid S. Pilyugin, Simon Pustilnik, Petri Väisänen, David Buckley, Yas Hashimoto, Nicola Loaring, Encarni Romero, Martin Still, Eric B. Burgh, Kenneth Nordsieck

Research output: Contribution to journalArticle

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Abstract

In this work we present the first spectroscopic results obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. We find that the Sagittarius dwarf spheroidal galaxy (Sgr) contains a youngest stellar population with [O/H] ≈ -0.2 and age t > 1 Gyr, and an oldest population with [O/H] = -2.0. The values are based on spectra of two planetary nebulae (PNe), using empirical abundance determinations. We calculated abundances for O, N, Ne, Ar, S, Cl, Fe, C and He. We confirm the high abundances of PN StWr 2-21 with 12 + log(O/H) = 8.57 ± 0.02 dex. The other PN studied, BoBn 1, is an extraordinary object in that the neon abundance exceeds that of oxygen. The abundances of S, Ar and Cl in BoBn 1 yield the original stellar metallicity, corresponding to 12 + log(O/H) = 6.72 ± 0.16 dex which is 1/110 of the solar value. The actual [O/H] is much higher: third dredge-up enriched the material by a factor of ∼12 in oxygen, ∼240 in nitrogen and ∼70 in neon. Neon as well as nitrogen and oxygen content may have been produced in the intershell of low-mass asymptotic giant branch (AGB) stars. Well defined broad WR lines are present in the spectrum of StWr 2-21 and absent in the spectrum of BoBn 1. This puts the fraction of [WR]-type central PNe stars to 67 per cent for dSph galaxies.

Original languageEnglish
Pages (from-to)1667-1678
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Volume388
Issue number4
DOIs
Publication statusPublished - 2008 Aug 1

Fingerprint

planetary nebulae
metallicity
spectroscopy
neon
telescopes
oxygen
nitrogen
young population
asymptotic giant branch stars
dredger
dwarf galaxies
galaxies
stars

Keywords

  • Galaxies: individual: Sagittarius dwarf spheroidal
  • Planetary nebulae: general
  • Stars: abundances
  • Stars: mass-loss

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Kniazev, A. Y., Zijlstra, A. A., Grebel, E. K., Pilyugin, L. S., Pustilnik, S., Väisänen, P., ... Nordsieck, K. (2008). The metallicity extremes of the Sagittarius dSph: SALT spectroscopy of PNe. Monthly Notices of the Royal Astronomical Society, 388(4), 1667-1678. https://doi.org/10.1111/j.1365-2966.2008.13435.x

The metallicity extremes of the Sagittarius dSph : SALT spectroscopy of PNe. / Kniazev, Alexei Y.; Zijlstra, Albert A.; Grebel, Eva K.; Pilyugin, Leonid S.; Pustilnik, Simon; Väisänen, Petri; Buckley, David; Hashimoto, Yas; Loaring, Nicola; Romero, Encarni; Still, Martin; Burgh, Eric B.; Nordsieck, Kenneth.

In: Monthly Notices of the Royal Astronomical Society, Vol. 388, No. 4, 01.08.2008, p. 1667-1678.

Research output: Contribution to journalArticle

Kniazev, AY, Zijlstra, AA, Grebel, EK, Pilyugin, LS, Pustilnik, S, Väisänen, P, Buckley, D, Hashimoto, Y, Loaring, N, Romero, E, Still, M, Burgh, EB & Nordsieck, K 2008, 'The metallicity extremes of the Sagittarius dSph: SALT spectroscopy of PNe', Monthly Notices of the Royal Astronomical Society, vol. 388, no. 4, pp. 1667-1678. https://doi.org/10.1111/j.1365-2966.2008.13435.x
Kniazev AY, Zijlstra AA, Grebel EK, Pilyugin LS, Pustilnik S, Väisänen P et al. The metallicity extremes of the Sagittarius dSph: SALT spectroscopy of PNe. Monthly Notices of the Royal Astronomical Society. 2008 Aug 1;388(4):1667-1678. https://doi.org/10.1111/j.1365-2966.2008.13435.x
Kniazev, Alexei Y. ; Zijlstra, Albert A. ; Grebel, Eva K. ; Pilyugin, Leonid S. ; Pustilnik, Simon ; Väisänen, Petri ; Buckley, David ; Hashimoto, Yas ; Loaring, Nicola ; Romero, Encarni ; Still, Martin ; Burgh, Eric B. ; Nordsieck, Kenneth. / The metallicity extremes of the Sagittarius dSph : SALT spectroscopy of PNe. In: Monthly Notices of the Royal Astronomical Society. 2008 ; Vol. 388, No. 4. pp. 1667-1678.
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AU - Zijlstra, Albert A.

AU - Grebel, Eva K.

AU - Pilyugin, Leonid S.

AU - Pustilnik, Simon

AU - Väisänen, Petri

AU - Buckley, David

AU - Hashimoto, Yas

AU - Loaring, Nicola

AU - Romero, Encarni

AU - Still, Martin

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N2 - In this work we present the first spectroscopic results obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. We find that the Sagittarius dwarf spheroidal galaxy (Sgr) contains a youngest stellar population with [O/H] ≈ -0.2 and age t > 1 Gyr, and an oldest population with [O/H] = -2.0. The values are based on spectra of two planetary nebulae (PNe), using empirical abundance determinations. We calculated abundances for O, N, Ne, Ar, S, Cl, Fe, C and He. We confirm the high abundances of PN StWr 2-21 with 12 + log(O/H) = 8.57 ± 0.02 dex. The other PN studied, BoBn 1, is an extraordinary object in that the neon abundance exceeds that of oxygen. The abundances of S, Ar and Cl in BoBn 1 yield the original stellar metallicity, corresponding to 12 + log(O/H) = 6.72 ± 0.16 dex which is 1/110 of the solar value. The actual [O/H] is much higher: third dredge-up enriched the material by a factor of ∼12 in oxygen, ∼240 in nitrogen and ∼70 in neon. Neon as well as nitrogen and oxygen content may have been produced in the intershell of low-mass asymptotic giant branch (AGB) stars. Well defined broad WR lines are present in the spectrum of StWr 2-21 and absent in the spectrum of BoBn 1. This puts the fraction of [WR]-type central PNe stars to 67 per cent for dSph galaxies.

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KW - Stars: mass-loss

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