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In half a year Gaia is expected to largely solve the problem of inaccurate distances within the Galaxy, with a billion+ stars having trigonometric parallax errors at a level of a few per-cent. Similarly, their proper motions will reach exquisite accuracy by the standards we used so far. But radial velocities could be measured only for a rather smaller sample by Gaia. I will discuss important physical applications of accurate radial velocities and how to obtain them with ground-based spectroscopic surveys where Galah is the primary asset. I will argue that while accuracy of a few km/s is needed for studies of Galactic kinematics a measurement at a 100 m/s level opens up statistical studies of kinematics within the stellar atmosphere and kinematics of stars within a cluster or a stream. And Galah is getting there. |
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