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 ~ 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 6 400 deg² to a magnitude limit of V ~ 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. Based on observations collected at the European Southern Observatory, Chile (Proposal IDs 145.B-0009 and 63.L-0148). Table A.1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/375/366