GAIA accuracy on radial velocities assessed from a synthetic spectra database

Free access article

Issue		A&A Volume 386, Number 2, May I 2002


Page(s)		748 - 756
Section		Instruments, observational techniques and data processing
DOI		http://dx.doi.org/10.1051/0004-6361:20020250

A&A 386, 748-756 (2002)
DOI: 10.1051/0004-6361:20020250

GAIA accuracy on radial velocities assessed from a synthetic spectra database

T. Zwitter

University of Ljubljana, Department of Physics, Jadranska 19, 1000 Ljubljana, Slovenia

(Received 29 October 2001 / Accepted 14 February 2002)

Abstract
Spectrograph aboard the GAIA satellite operates in the near-IR, in the 8490-8740 Å window accessible also from the ground. The most important parameter yet to be determined is the spectral resolution. Realistic estimates of the zodiacal light background are obtained and a total of $2\times 10^5$ correlation runs are used to study the accuracy of radial velocity measured by the spectrograph as a function of resolution, magnitude of the target, its spectral type and luminosity class. Accuracy better than 2 km s ^-1 is achievable for bright stars if a high enough dispersion is chosen. Radial velocity error of 5 km s ^-1 is at V=17.5 for Cepheids and at 17.7 for horizontal branch stars. Even for very faint objects, with spectra dominated by background and readout noise, the optimal dispersion is still in the 0.25/0.75 Å/pix range. This is also true for complicated cases such as spectroscopic binaries or if information other than radial velocity, i.e. abundances of individual elements or stellar rotation velocity, is sought after. The results can be scaled to assess performance of future ground based instruments.

Key words: stars: kinematics -- surveys -- space vehicles: instruments -- techniques: radial velocities

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