We examine the metallicity distribution function ( MDF ) and fraction of carbon-enhanced metal-poor ( CEMP ) stars in a sample that includes 86 stars with [ Fe/H ] \leq - 3.0 , based on high-resolution , high-S/N spectroscopy , of which some 32 objects lie below [ Fe/H ] = - 3.5 .
After accounting for the completeness function , the “ corrected ” MDF does not exhibit the sudden drop at [ Fe/H ] = - 3.6 that was found in recent samples of dwarfs and giants from the Hamburg/ESO survey .
Rather , the MDF decreases smoothly down to [ Fe/H ] = - 4.1 .
Similar results are obtained from the “ raw ” MDF .
We find the fraction of CEMP objects below [ Fe/H ] = - 3.0 is 23 \pm 6 % and 32 \pm 8 % when adopting the Beers & Christlieb and Aoki et al . CEMP definitions , respectively .
The former value is in fair agreement with some previous measurements , which adopt the Beers & Christlieb criterion .