The stellar content of the Hamburg/ESO survey

We present a sample of 403 faint high latitude carbon (FHLC) stars selected from the digitized objective prism plates of the Hamburg/ESO Survey (HES). Because of the ∼15 Å spectral resolution and high signal-to-noise ratio of the HES prism spectra, our automated procedure based on the detection of C2 and CN molecular bands permits high-confidence identification of carbon stars without the need for follow-up spectroscopy. From a set of 329 plates (87 % of the survey), covering deg2 to a magnitude limit of , we analyze the selection efficiency and effective surface area of the HES FHLC survey to date. The surface density of FHLC stars that we detect ( deg-2) is 2-4 times higher than that of previous objective prism and CCD surveys at high galactic latitude, even though those surveys claimed a limiting magnitude up to 1.5 magnitudes fainter. This attests to the highest selection sensitivity yet achieved for these types of stars.