Identifying stellar streams in the first RAVE public data release

We have searched for and detected stellar streams or moving groups in the solar neighborhood, using the data provided by the first RAVE public data release. This analysis is based on distances to RAVE stars estimated from a color-magnitude relation calibrated on Hipparcos stars. Our final sample consists of 7015 stars selected to be within 500 pc of the Sun and to have distance errors better than 25%. Together with radial velocities from RAVE and proper motions from various databases, there are estimates for all six phase-space coordinates of the stars in the sample. We characterize the orbits of these stars through suitable proxies for their angular momentum and eccentricity and compare the observed distribution with the expectations from a smooth distribution. We identify at least four phase-space overdensities'' of stars on very similar orbits in the solar neighborhood. We estimate the statistical significance of these overdensities by Monte Carlo simulations. Three have been identified previously: the Sirius and Hercules moving groups and a stream found independently in 2006 by Arifyanto & Fuchs and Helmi et al. In addition, we find a new stream candidate on a quite radial orbit, suggesting an origin external to the Milky Way's disk. Also, there is evidence for the Arcturus stream and the Hyades-Pleiades moving group in the sample. The detections are further supported by analyzing the stellar distribution in velocity and angular momentum space using the Monte Carlo simulations. We find that the significance of overdensities is comparable, independent of the space in which the stream search is conducted. This analysis, using only a minute fraction of the final RAVE data set, shows the power of this experiment to probe the phase-space substructure of stars around the Sun.