Sydney observatory Galactic survey Potential for detection of extreme disk-crossing stars

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 B - V. 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 1/2° 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 CMC encounter.