Improved distances and ages for stars common to TGAS and RAVE

TL;DR

This study combines Gaia parallaxes with RAVE spectrophotometric distances to produce more accurate stellar distances and ages, revealing biases and uncertainties in current catalogues and providing a valuable dataset for galactic studies.

Contribution

It introduces a combined distance estimation method that improves accuracy over individual methods and assesses the reliability of Gaia and RAVE distance estimates.

Findings

Combined distances are on average twice as precise as RAVE-only.

Distances to low log g stars are overestimated and less reliable.

Gaia uncertainties may be smaller than reported.

Abstract

We combine parallaxes from the first Gaia data release with the spectrophotometric distance estimation framework for stars in the fifth RAVE survey data release. The combined distance estimates are more accurate than either determination in isolation - uncertainties are on average two times smaller than for RAVE-only distances (three times smaller for dwarfs), and 1.4 times smaller than TGAS parallax uncertainties (two times smaller for giants). We are also able to compare the estimates from spectrophotometry to those from Gaia, and use this to assess the reliability of both catalogues and improve our distance estimates. We find that the distances to the lowest log g stars are, on average, overestimated and caution that they may not be reliable. We also find that it is likely that the Gaia random uncertainties are smaller than the reported values. As a byproduct we derive ages for the RAVE stars, many with relative uncertainties less than 20 percent. These results for 219566 RAVE sources have been made publicly available, and we encourage their use for studies that combine the radial velocities provided by RAVE with the proper motions provided by Gaia. A sample that we believe to be reliable can be found by taking only the stars with the flag notification flag_any=0