The recent star formation history of the Hipparcos solar neighbourhood

Abstract

We use data from the Hipparcos catalogue to construct colour-magnitude diagrams for the solar neighbourhood, which are then treated using advanced Bayesian analysis techniques to derive the star formation history, $SFR(t)$, of this region over the last 3 Gyr. The method we use allows the recovery of the underlying $SFR(t)$ without the need of assuming any {\it a priori} structure or condition on $SFR(t)$, and hence yields a highly objective result. The remarkable accuracy of the data permits the reconstruction of the local $SFR(t)$ with an unprecedented time resolution of $\approx 50 $ Myr. A $SFR(t)$ having an oscillatory component of period $\approx 0.5$ Gyr is found, superimposed on a small level of constant star formation activity. Problems arising from the non-uniform selection function of the Hipparcos satellite are discussed and treated. Detailed statistical tests are then performed on the results, which confirm the inferred $SFR(t)$ to be compatible with the observed distribution of stars.