A new visual -- near-infrared diagnostic to estimate the metallicity of   cluster and field dwarf stars
  We present a theoretical calibration of a new metallicity diagnostic based on the Stroemgren index m1 and on visual -- near-infrared (NIR) colors to estimate the global metal abundance of cluster and field dwarf stars. To perform the metallicity calibration we adopt alpha-enhanced evolutionary models transformed into the observational plane by using atmosphere models computed adopting the same chemical mixture. We apply the new visual - NIR Metallicity-Index-Color (MIC) relations to two different samples of field dwarfs and we find that the difference between photometric estimates and spectroscopic measurements is on average smaller than 0.1 dex, with a dispersion smaller than sigma = 0.3 dex. We apply the same MIC relations to a metal-poor (M 92) and a metal-rich (47 Tuc) globular cluster. We find a peak of -2.01+/-0.08 (sigma = 0.30 dex) and -0.47+/-0.01 (sigma = 0.42 dex), respectively. 
Annalisa Calamida (OAR-INAF), M. Monelli, A. P. Milone (IAC), G. Bono   (Univ. Tor Vergata), A. Pietrinferni (OACTe-INAF), E...
astro-ph.SR