The stellar content of the Hamburg/ESO survey ^*

II. A large, homogeneously-selected sample of high latitude carbon stars

¹ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany e-mail: dreimers@hs.uni-hamburg.de
² Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02140, USA e-mail: pgreen@cfa.harvard.edu
³ Institut für Physik, Universität Potsdam, Am Neuen Palais 10, 14469 Potsdam, Germany e-mail: lutz@astro.physik.uni-potsdam.de

Corresponding author: N. Christlieb, nchristlieb@hs.uni-hamburg.de

Received: 26 April 2001
Accepted: 5 June 2001

Abstract

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.