K dwarfs and the chemical evolution of the solar cylinder

Abstract

K dwarfs have lifetimes older than the present age of the Galactic disc, and are thus ideal stars for investigating the chemical evolution of the disc. We have developed several photometric metallicity indicators for K dwarfs, based on a sample of accurate spectroscopic metallicities for 34 disc and halo G and K dwarfs. The photometric metallicities lead us to develop a metallicity index for K dwarfs based only on their position in the colour–absolute‐magnitude diagram. Metallicities have been determined for 431 single K dwarfs drawn from the Hipparcos catalogue, selecting the stars by absolute magnitude and removing multiple systems. The sample is essentially a complete reckoning of the metal content in nearby K dwarfs. We use stellar isochrones to mark the stars by mass, and select a subset of 220 of the stars, which is complete within a narrow mass interval. We fit the data with a model of the chemical evolution of the solar cylinder. We find that only a modest cosmic scatter is required to fit our age–metallicity relation. The model assumes two main infall episodes for the formation of the halo‐thick disc and thin disc, respectively. The new data confirm that the solar neighbourhood formed on a long time‐scale of the order of 7 Gyr.

The chemical evolution of a Milky Way-like galaxy: the importance of a cosmologically motivated infall law

“…This is the relative number of G-dwarf stars as a function of [Fe/H]. We have used the data from Rocha-Pinto & Maciel (1996), Kotoneva (2002), Jorgensen (2000 and . Our predicted metallicity distributions are shown in Fig.…”

Evolution of deuterium, $^{\rm 3}$He and $^{\rm 4}$He in the Galaxy

“…A good chemical evolution model should be in agreement with what is called the minimum set of observational constraints, among which the most important is the G-dwarf metallicity distribution (Chiappini et al 1997;Kotoneva et al 2002). In Table 5, the predicted and observed present-day quantities are shown.…”

Chemical evolution models for spiral disks: the Milky Way, M 31, and M 33

“…Boissier & Prantzos (1999), filled circles for Renda et al (2005), and dot-dot-dashed lines for Chang et al (1999). Right panel shows a comparison between our model (labelled this work in Table 1) and other dwarf distributions: solid thin line is the model prediction, solid thick line represents Holmberg et al (2007) distribution while the dotted one and the dashed line are the distributions of Kotoneva (2002) and Rocha-Pinto & Maciel (1996), respectively.…”