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Reading the Chemical Evolutionary Signatures of Dwarf Spheroial Galaxies

Ben Hendricks (Heidelberg)

Dwarf spheroidal (dSph) galaxies are the smallest, closest and most
abundand galaxies in the Universe
and therefore excellent laboratories to study star formation (SF) history
and chemical evolution on the smallest scale.
Particularly the newest generation of multi-object spectrographs have
helped to unveil details about their dynamical and chemical properties in
the last couple of years.
However, there is still a lack of sufficiently large, homogeneous
spectroscopic datasets for sufficiently many individual dSphs,
and therefore we are just beginning to understand the physical concepts
behind the observed properties.
Here, I present chemical abundances for iron (Fe) and three alpha-elements
(Mg, Si, Ti) from high-resolution spectra for a large sample of field
stars in the Fornax dSph.
For the first time, we are able to resolve and trace the chemical
evolution of Fornax over almost its entire age.
Surprisingly, we find that Fornax experienced a very weak star formation
efficiency at early times, not in agreement with either direct comparisons
of observations in other dSphs, nor with chemical evolutionary models.
The scope of this talk is to present the results from our chemical
analysis and put them in a general context of our understanding of
chemical evolution in dSphs, and its key-regulating factors.
On this basis, possible (and impossible) evolutionary scenarios for Fornax
are discussed and compared with model predictions.