Sydney observatory Galactic survey^*

Potential for detection of extreme disk-crossing stars

¹ Observatoire astronomique, Université Louis Pasteur, CNRS, 11 rue de l'Université, 67000 Strasbourg, France e-mail: fresneau@astro.u-strasbg.fr
² Department of Physics, Macquarie University, Sydney 2109, New South Wales, Australia e-mail: alanv@ics.mq.edu.au
³ Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK e-mail: rwa@ast.cam.ac.uk

Received: 23 January 2007
Accepted: 2 May 2007

Abstract

Context.First Epoch astrometric and radiometric information of a survey in the optical along the Galactic fourth quadrant is archived for further analysis in the time-domain.

Aims.A photographic survey of 1.9  10⁶ stars down to B-magnitude 14 ± 0.5 along the galactic meridian l = (330 ± 5)°, -64° ≤ b ≤ -7° and along the galactic equator 272° ≤ l ≤ 341°, b ≤ 7°, is provided from century old astrographic plates of Sydney Observatory. Stellar candidates to investigate the Galaxy disk kinematics up to a distance of 1 kpc from the Sun are tentatively selected.

Methods.The early data are combined with late epoch observations into a set of 4.8  10⁵ stars with significant proper motion μ ≥ 0.005´´ yr^-1 and approximate color . The selection effects and the kinematical bias on the stellar system are investigated. F-G stellar candidates with a mean transverse velocity dispersion of 45 km s^-1 are suggested.

Results.The spin rate of ° pc^-1 of the velocity ellipsoid along its long axis is observed over half a thickness of 25 pc of the galactic disk for stars at an estimated distance D ≤ 300 pc from the Sun.

Conclusions.A catalogue of 4.8  10⁵ stars is provided for further investigation of the galactic disk heating by transient spiral wave or by GMC encounter.