We describe a new method to search for metal-poor candidates from the Hamburg/ESO objective-prism survey ( HES ) based on identifying stars with apparently strong CH G-band strengths for their colors .
The hypothesis we exploit is that large over-abundances of carbon are common among metal-poor stars , as has been found by numerous studies over the past two decades .
The selection was made by considering two line indices in the 4300 Å region , applied directly to the low-resolution prism spectra .
This work also extends a previously published method by adding bright sources to the sample .
The spectra of these stars suffer from saturation effects , compromising the index calculations and leading to an undersampling of the brighter candidates .
A simple numerical procedure , based on available photometry , was developed to correct the line indices and overcome this limitation .
Visual inspection and classification of the spectra from the HES plates yielded a list of 5,288 new metal-poor ( and by selection , carbon-rich ) candidates , which are presently being used as targets for medium-resolution spectroscopic follow-up .
Estimates of the stellar atmospheric parameters , as well as carbon abundances , are now available for 117 of the first candidates , based on follow-up medium-resolution spectra obtained with the SOAR 4.1m and Gemini 8m telescopes .
We demonstrate that our new method improves the metal-poor star fractions found by our pilot study by up to a factor of three in the same magnitude range , as compared with our pilot study based on only one CH G-band index .
Our selection scheme obtained roughly a 40 % success rate for identification of stars with [ Fe/H ] < -1.0 ; the primary contaminant is late-type stars with near solar abundances and , often , emission line cores that filled in the Ca ii K line on the prism spectrum .
Because the selection is based on carbon , we greatly increase the numbers of known CEMP stars from the HES with intermediate metallicities -2.0 < [ Fe/H ] < -1.0 , which previous survey efforts undersampled .
There are eight newly discovered stars with [ Fe/H ] < -3.0 in our sample , including two with [ Fe/H ] < -3.5 .