We report on the distribution of metallicities , [ Fe/H ] , for very metal-poor stars in the halo of the Galaxy .
Although the primary information on the nature of the Metallicity Distribution Function ( MDF ) is obtained from the two major recent surveys for metal-poor stars , the HK survey of Beers and collaborators , and the Hamburg/ESO Survey of Christlieb and collaborators , we also discuss the MDF derived from the publicly available database of stellar spectra and photometry contained in the third data release of the Sloan Digital Sky Survey ( SDSS DR-3 ) .
Even though the SDSS was not originally planned as a stellar survey , significant numbers of stars have been observed to date – DR-3 contains spectroscopy for over 70,000 stars , at least half of which are suitable for abundance determinations .
There are as many very metal-poor ( [ Fe/H ] < -2.0 ) stars in DR-3 as have been obtained from all previous survey efforts combined .
We also discuss prospects for significant expansion of the list of metal-poor stars to be obtained from the recently funded extension of the SDSS , which includes the project SEGUE : Sloan Extension for Galactic Understanding and Exploration .