The stellar content of the Hamburg/ESO survey - II. A large, homogeneously-selected sample of high latitude carbon stars

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 similar to 15 Angstrom spectral resolution and high signal-to-noise ratio of the HES prism spectra, our automated procedure based on the detection of C-2 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 6 400 deg(2) to a magnitude limit of V similar to 16.5, 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 (0.072 +/- 0.005 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.