Abundances of Extremely Metal-poor Star Candidates

We present chemical abundances for 110 stars identified in objective-prismsurveys as candidates to be very metal-poor. The abundances are derived fromhigh S/N, intermediate-resolution spectra obtained with the Keck ObservatoryEchelle Spectrometer and Imager. An additional 25 stars with well-determinedabundances ranging from [Fe/H]$=-1.5$ and -3.2 were observed and the resultsused to help calibrate our analysis and determine the accuracy of our abundancedeterminations. Abundances for the program stars were measured for Fe, Mg, Ca,Ti, Cr and Ba with an accuracy of approximately 0.3 dex. 53 of the stars in oursample have [Fe/H]<= -2, 22 have [Fe/H]<= -2.5 and 13 stars have [Fe/H]<= -2.9.Surprisingly, approximately one third of the sample is relatively metal richwith [Fe/H]>-1.5. In addition to identifying a number of extremely metal-poorstars, this study also shows that moderate-resolution spectra obtained with theKeck Echelle Spectrometer and Imager yield relatively accurate abundances forstars as faint as V=14 in modest exposure time (~20 minutes). This capabilitywill prove useful if the so-far elusive stars at [Fe/H]<-4 turn out to bemostly fainter than V=15.Comment: 60 pages, 10 figures, Accepted for publication in the A