The GSC-II-based survey of ancient cool white dwarfs

I. The sample of spectroscopically confirmed white dwarfs

¹ INAF – Osservatorio Astronomico di Torino, 10025 Pino Torinese, Italy e-mail: carollo@to.astro.it
² Cambridge Astronomical Survey Unit, Institute of Astronomy, Madingley Road,Cambridge, CB3 0HA, UK
³ Space Telescope Science Institute, 3700 San Martin Drive Baltimore, MD 21218, USA
⁴ INAF – Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy

Received: 27 August 2005
Accepted: 2 November 2005

Abstract

The GSC-II white dwarf survey was designed to identify faint and high proper motion objects, which we used to define a new and independent sample of cool white dwarfs. With this survey we aim to derive new constraints on the halo white dwarf space density. Also, these data can provide information on the age of thick disk and halo through the analysis of the luminosity function. On the basis of astrometric and photometric parameters, we selected candidates with and in an area of 1150 square degrees. Then, we separated white dwarfs from late type dwarfs and subdwarfs by means of the reduced proper motion diagram. Finally, spectroscopic follow-up observations were carried out to confirm the white dwarf nature of the selected candidates. We found 41 white dwarfs of which 24 are new discoveries. Here we present the full sample and for each object provide positions, absolute proper motions, photometry, and spectroscopy.