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Distance determination for RAVE stars using stellar models. III. The nature of the RAVE survey and Milky Way chemistry
We apply the method of Burnett & Binney (2010, MNRAS, 407, 339) forthe determination of stellar distances and parameters to the internalcatalogue of the RAdial Velocity Experiment (RAVE; Steinmetz et al.2006, AJ, 132, 1645). Subsamples of stars that either have Hipparcosparallaxes or belong to well-studied clusters inspire confidence in theformal errors. Distances to dwarfs cooler than ~6000 K appear to beunbiased, but those to hotter dwarfs tend to be too small by ~10% of theformal errors. Distances to giants tend to be too large by about thesame amount. The median distance error in the whole sample of 216 000stars is 28% and the error distribution is similar for both giants anddwarfs. Roughly half the stars in the RAVE survey are giants. The giantfraction is largest at low latitudes and in directions towards theGalactic Centre. Near the plane the metallicity distribution isremarkably narrow and centred on [M/H] = -0.04 dex; with increasing |z|it broadens out and its median moves to [M/H] ? -0.5. Mean age as afunction of distance from the Galactic centre and distance |z| from theGalactic plane shows the anticipated increase in mean age with |z|.
| UBV(RI)C photometry of Hipparcos red stars
We present homogeneous and standardized UBV(RI)C photometryfor nearly 550 M stars selected from the Hipparcos satellite data baseusing the following selection criteria: lack of obvious variability (noHipparcos variability flag); δ<+10°(V-I)>1.7 and Vmagnitude fainter than about 7.6. Comparisons are made between thecurrent photometry, other ground-based data sets and Hipparcosphotometry. We use linear discriminant analysis to determine aluminosity segregation criterion for late-type stars, and principalcomponent analysis to study the statistical structure of the colourindices and to calibrate absolute magnitude in terms of (V-I) for thedwarf stars. Various methods are used to determine the mean absolutemagnitude of the giant stars. We find 10 dwarf stars, apparentlypreviously unrecognized (prior to Hipparcos) as being within 25pc,including five within 20pc.
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