TY - JOUR
T1 - The metallicity extremes of the Sagittarius dSph
T2 - SALT spectroscopy of PNe
AU - Kniazev, Alexei Y.
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
AU - Burgh, Eric B.
AU - Nordsieck, Kenneth
PY - 2008/8
Y1 - 2008/8
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.
AB - 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.
KW - Galaxies: individual: Sagittarius dwarf spheroidal
KW - Planetary nebulae: general
KW - Stars: abundances
KW - Stars: mass-loss
UR - https://www.scopus.com/pages/publications/49249138390
UR - https://www.scopus.com/pages/publications/49249138390#tab=citedBy
U2 - 10.1111/j.1365-2966.2008.13435.x
DO - 10.1111/j.1365-2966.2008.13435.x
M3 - Article
AN - SCOPUS:49249138390
SN - 0035-8711
VL - 388
SP - 1667
EP - 1678
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -