Examining the relationships between colour, Teff, and [M/H] for APOGGE K and M dwarfs
arxiv:1605.03732
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 g−r is not a good indicator of metallicity for near-solar metallicity early-M dwarfs. We confirm that J−KS colour is strongly dependent on metallicity, and find that W1−W2 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 r−z and J−KS colours, but poor agreement in u−g, g−r, and W1−W2. 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 r−z colour combined with either [M/H] or W1−W2 colour, and for [M/H] as a function of r−z and W1−W2 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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