Helmi, Amina; Irwin, M. J.; Tolstoy, E.; Battaglia, G.; Hill, V.; Jablonka, P.; Venn, K.; Shetrone, M.; Letarte, B.; Arimoto, N.; Abel, T.; Francois, P.; Kaufer, A.; Primas, F.; Sadakane, K.; Szeifert, T.
Bibliographical reference
The Astrophysical Journal, Volume 651, Issue 2, pp. L121-L124.
Advertised on:
11
2006
Journal
Citations
193
Refereed citations
152
Description
As part of the Dwarf galaxies Abundances and Radial-velocities Team
(DART) program, we have measured the metallicities of a large sample of
stars in four nearby dwarf spheroidal galaxies (dSph's): Sculptor,
Sextans, Fornax, and Carina. The low mean metal abundances and the
presence of very old stellar populations in these galaxies have
supported the view that they are fossils from the early universe.
However, contrary to naive expectations, we find a significant lack of
stars with metallicities below [Fe/H]~-3 dex in all four systems. This
suggests that the gas that made up the stars in these systems had been
uniformly enriched prior to their formation. Furthermore, the metal-poor
tail of the dSph metallicity distribution is significantly different
from that of the Galactic halo. These findings show that the progenitors
of nearby dSph's appear to have been fundamentally different from the
building blocks of the Milky Way, even at the earliest epochs.
Based on FLAMES/GIRAFFE observations collected at the European Southern
Observatory, proposal 171.B-0588.