New H-band Stellar Spectral Libraries for the SDSS-III/APOGEE survey
Résumé
The Sloan Digital Sky Survey--III (SDSS--III) Apache Point Observatory Galactic Evolution Experiment (APOGEE) has obtained high resolution (R ∼ 22,500), high signal-to-noise ratio (> 100) spectra in the H−band (∼1.5−1.7 μm) for about 146,000 stars in the Milky Way galaxy. We have computed spectral libraries with effective temperature (Teff) ranging from 3500 to 8000 K for the automated chemical analy\-sis of the survey data. The libraries, used to derive stellar parameters and abundances from the APOGEE spectra in the SDSS--III data release 12 (DR12), are based on ATLAS9 model atmospheres and the ASSϵT spectral synthesis code. We present a second set of libraries based on MARCS model atmospheres and the spectral synthesis code Turbospectrum. The ATLAS9/ASSϵT (Teff = 3500−8000 K) and MARCS/Turbospectrum (Teff = 3500−5500 K) grids cover a wide range of metallicity (−2.5 ≤ [M/H] ≤ +0.5 dex), surface gravity (0 ≤ log g ≤ 5 dex), microturbulence (0.5 ≤ ξ ≤ 8 km~s−1), carbon (−1 ≤ [C/M] ≤ +1 dex), nitrogen (−1 ≤ [N/M] ≤ +1 dex), and α-element (−1 ≤ [α/M] ≤ +1 dex) variations, having thus seven dimensions. We compare the ATLAS9/ASSϵT and MARCS/Turbospectrum libraries and apply both of them to the analysis of the observed H−band spectra of the Sun and the K2 giant Arcturus, as well as to a selected sample of well-known giant stars observed at very high-resolution. The new APOGEE libraries are publicly available and can be employed for chemical studies in the H−band using other high-resolution spectrographs