Evidence for a signature of the galactic bar in the solar neighbourhood

Abstract

Using available kinematical data for a subsample of NLTT stars from the HIPPARCOS mission we confirm the existence of a previously reported local anomaly in the (u,v) plane: the mean motion /line{u} for old disc stars, with v < -30 km s(-1) , is largely positive (+19 +/- 9 km s(-1) w.r.t. the Galactic Center). With the use of the newest global self-consistent numerical models of our Galaxy (Fux \cite{fux}), we show that a bar could be responsible for this observed velocity anomaly. A fraction of our stars have bar perturbed ``hot'' orbits, allowing them to erratically wander from inside the bar to regions outside the corotation, in particular through the solar neighbourhood. Based on data from the ESA HIPPARCOS satellite, on photometric data collected at the Swiss telescope at La Silla and on data collected with CORAVELs at the Haute Provence Observatory (France) and at ESO, La Silla Chile