The SkyMapper Southern Sky Survey is carrying out a search for the most
metal-poor stars in the Galaxy. It identifies candidates by way of its unique
filter set that allows for estimation of stellar atmospheric parameters. The
set includes a narrow filter centered on the Ca II K 3933A line, enabling a
robust estimate of stellar metallicity. Promising candidates are then confirmed
with spectroscopy. We present the analysis of Magellan-MIKE high-resolution
spectroscopy of 122 metal-poor stars found by SkyMapper in the first two years
of commissioning observations. 41 stars have [Fe/H] <= -3.0. Nine have [Fe/H]
<= -3.5, with three at [Fe/H] ~ -4. A 1D LTE abundance analysis of the elements
Li, C, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Sr, Ba and Eu shows
these stars have [X/Fe] ratios typical of other halo stars. One star with low
[X/Fe]
[X/Fe values appears to be "Fe-enhanced," while another star has an extremely
large [Sr/Ba] ratio: >2. Only one other star is known to have a comparable
value. Seven stars are "CEMP-no" stars ([C/Fe] > 0.7, [Ba/Fe] < 0). 21 stars
exhibit mild r-process element enhancements (0.3 <=[Eu/Fe] < 1.0), while four
stars have [Eu/Fe] >= 1.0. These results demonstrate the ability to identify
extremely metal-poor stars from SkyMapper photometry, pointing to increased
sample sizes and a better characterization of the metal-poor tail of the halo
metallicity distribution function in the future.Comment: Minor corrections to text, missing data added to Tables 3 and 4;
updated to match published version. Complete tables included in sourc
