Examining the relationships between colour, Teff, and [M/H] for APOGGE K and M dwarfs

Sarah J. Schmidt, Erika L. Wagoner, Jennifer A. Johnson, et al

doi:10.1093/mnras/stw1139

arxiv:1605.03732

ads:2016MNRAS.460.2611S

Published:

Published in: MNRAS

Abstract:

We present the effective temperatures (Teff), metallicities, and colours in SDSS, 2MASS, and WISE filters, of a sample of 3834 late-K and early-M dwarfs selected from the Sloan Digital Sky Survey APOGEE spectroscopic survey ASPCAP catalog. We confirm that ASPCAP Teff values between 3550 K<Teff<4200 K are accurate to 100 K compared to interferometric Teff values. In that same Teff range, ASPCAP metallicities are accurate to 0.18 dex between 1.0<[M/H]<0.2. For these cool dwarfs, nearly every colour is sensitive to both Teff and metallicity. Notably, we find that gr is not a good indicator of metallicity for near-solar metallicity early-M dwarfs. We confirm that JKS colour is strongly dependent on metallicity, and find that W1W2 colour is a promising metallicity indicator. Comparison of the late-K and early-M dwarf colours, metallicities, and Teff to those from three different model grids shows reasonable agreement in rz and JKS colours, but poor agreement in ug, gr, and W1W2. Comparison of the metallicities of the KM dwarf sample to those from previous colour-metallicity relations reveals a lack of consensus in photometric metallicity indicators for late-K and early-M dwarfs. We also present empirical relations for Teff as a function of rz colour combined with either [M/H] or W1W2 colour, and for [M/H] as a function of rz and W1W2 colour. These relations yield Teff to 100 K and [M/H] to 0.18 dex precision with colours alone, for Teff in the range of 3550–4200 K and [M/H] in the range of 0.5–0.2.


Summary

This is an exploration of the relation between color, temperature, and metallity for low mass stars in the Sloan Digital Sky Survey (SDSS), the Two Micron All-Sky Survey (2MASS), and the Wide-field Infrared Survey Explorer (WISE). The colors, temperatures, and metallicities for K and M dwarfs with accurate infrared spectra are compared with isochrone model grids and color-metallicity relations. This can be used as a way to estimate the temperatures and metallicities in a large sample of such stars with colors but noisy spectra. These estimates can then be used in constructing a metallicity distribution function for low mass stars.

Contribution

This is primarily a continuation of my undergraduate thesis project with a much larger data set and more isochrones tested.

Recommended Citation

Sarah J. Schmidt et al. 2016, MNRAS 460, 2611

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