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

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 ratio ($>$ 100) spectra in the H$-$band ($\sim$1.5$-$1.7 $\mu$m) for about 146,000 stars in the Milky Way galaxy. We have computed spectral libraries with effective temperature ($T{}_{\mathrm{e}\mathrm{f}\mathrm{f}}$) 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 ASS$ϵ$T spectral synthesis code. We present a second set of libraries based on MARCS model atmospheres and the spectral synthesis code Turbospectrum. The ATLAS9/ASS$ϵ$T ($T{}_{\mathrm{e}\mathrm{f}\mathrm{f}}$ = 3500$-$8000 K) and MARCS/Turbospectrum ($T{}_{\mathrm{e}\mathrm{f}\mathrm{f}}$ = 3500$-$5500 K) grids cover a wide range of metallicity ($-$2.5 $\le$ [M/H] $\le$ $+$0.5 dex), surface gravity (0 $\le$ log $g$ $\le$ 5 dex), microturbulence (0.5 $\le$ $\xi$ $\le$ 8 km~s${}^{-1}$), carbon ($-$1 $\le$ [C/M] $\le$ $+$1 dex), nitrogen ($-$1 $\le$ [N/M] $\le$ $+$1 dex), and $\alpha$-element ($-$1 $\le$ [$\alpha$/M] $\le$ $+$1 dex) variations, having thus seven dimensions. We compare the ATLAS9/ASS$ϵ$T and MARCS/Turbospectrum libraries and apply both of them to the analysis of the observed H$-$band spectra of the Sun and the K2 giant Arcturus, as well as to a selected sample of well-known giant stars observed at very high-resolution. The new APOGEE libraries are publicly available and can be employed for chemical studies in the H$-$band using other high-resolution spectrographs.