New H-band Stellar Spectral Libraries for the SDSS-III/APOGEE survey

O. Zamora, D. A. Garcia-Hernandez, C. Allende Prieto, R. Carrera, L. Koesterke, B. Edvardsson, F. Castelli, B. Plez, D. Bizyaev, K. Cunha, A. E. Garcia Perez, B. Gustafsson, J. A. Holtzman, J. E. Lawler, S. R. Majewski, A. Manchado, Sz. Meszaros, N. Shane, M. Shetrone, V. V. Smith, G. Zasowski

Published 2015-02-18Version 1

The Sloan Digital Sky Survey--III (SDSS--III) Apache Point Observatory Galactic Evolution Experiment (APOGEE) has obtained high resolution (R $\sim$ 22,500), high signal-to-noise ($>$ 100) spectra in the H$-$band spectral region ($\sim$1.5$-$1.7 $\mu$m) for about 146,000 stars in the Milky Way galaxy. We have computed specific spectral libraries with effective temperature ($T\rm{_{eff}}$) ranging from 3500 to 8000 K for the automated chemical analysis of the survey data. The spectral 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 ASS$\epsilon$T spectral synthesis code. We present a second set of stellar spectral libraries based on MARCS model atmospheres and the spectral synthesis code Turbospectrum. The ATLAS9/ASS$\epsilon$T ($T\rm{_{eff}}$ = 3500$-$8000 K) and MARCS/Turbospectrum ($T\rm{_{eff}}$ = 3500$-$5500 K) grids of synthetic spectra cover a wide range of metallicity ($-$2.5 $\leq$ [M/H] $\leq$ $+$0.5 dex), surface gravity (0 $\leq$ log $g$ $\leq$ 5 dex), microturbulence (0.5 $\leq$ $\xi$ $\leq$ 8 km s$^{-1}$), carbon ($-$1 $\leq$ [C/M] $\leq$ $+$1 dex), nitrogen ($-$1 $\leq$ [N/M] $\leq$ $+$1 dex), and $\alpha$-elements ($-$1 $\leq$ [$\alpha$/M] $\leq$ $+$1 dex) variations, having thus seven dimensions. We compare the ATLAS9/ASS$\epsilon$T and MARCS/Turbospectrum spectral libraries and we apply both of them to the observed H$-$band spectra of the Sun and the K2 giant Arcturus, as well as to a selected sample of well-known giant stars observed at very high-resolution. The new APOGEE synthetic spectral libraries are publicly available online and can be employed for chemical studies in the H$-$band using other high-resolution spectrographs.