M giants at high galactic latitudes: an old metal-rich population?

Spectroscopic and photometric observations are presented for a sample of 227 late-M giants in the extended solar neighbourhood, catalogued by Stephenson using objective prism plates. The kinematics and scaleheight of these stars suggest that they belong to a mixed population, extending from the old thin disc to the thick disc. They show evidence of the differential galactic rotation predicted theoretically. Metallicities have been determined from a comparison of TiO band strengths and infrared colours with model atmospheres for late-type stars, and suggest a mean metallicity close to solar.