THE RAVE SPECTROSCOPIC SURVEY: RESULTS FROM THE FIRST 44 000 OBSERVED STARS

摘要

RAVE (RAdial Velocity Experiment) is a medium resolution all-sky spectroscopic survey conducted with the 150 fiber 6dF spectrograph at the UK-Schmidt telescope in Australia. The wavelength range (8430-8740 A) and resolving power (8500) are similar to those currently baselined for the Gaia spectroscopic observations (8480-8740 A and 11 500, respectively). The survey began on 11 April 2003 and by 1 September 2004 a total of 44 109 high galactic latitude field stars have been observed in the magnitude range 9 ≤ I_C ≤ 12, about three mag fainter than the Geneva-Copenhagen all-sky survey of solar neighbourhood solar-type dwarf stars. Cross-correlation against suitable synthetic spectral templates provides good radial velocities, the error distribution of which peaks at 1.0 km s~(-1) on I_C ≤ 10 stars, 1.3 km s~(-1) on 10 ≤ I_C ≤ 11 stars stars and 2.0 km s~(-1) for 11 ≤ I_C ≤ 12 stars. Preliminary results on atmospheric parameters obtained with a simplified automatic pipeline indicates errors of ～ 6% on T_(eff), 0.4 dex on [Fe/H] and 0.9 dex on log g for solar-type spectra of moderate to high S/N. Improvements in the continuum normalization, automatic pipeline and synthetic reference grid for the final data reduction and analysis are expected to further improve the performances in both radial velocities as well atmospheric parameters, especially when used in conjunction with optical and IR photometry available for most of the programme stars.