THE DATA REDUCTION PIPELINE FOR THE APACHE POINT OBSERVATORY GALACTIC EVOLUTION EXPERIMENT

Abstract

The Apache Point Observatory Galactic Evolution Experiment (APOGEE), part of\nthe Sloan Digital Sky Survey III, explores the stellar populations of the Milky\nWay using the Sloan 2.5-m telescope linked to a high resolution (R~22,500),\nnear-infrared (1.51-1.70 microns) spectrograph with 300 optical fibers. For\nover 150,000 predominantly red giant branch stars that APOGEE targeted across\nthe Galactic bulge, disks and halo, the collected high S/N (>100 per\nhalf-resolution element) spectra provide accurate (~0.1 km/s) radial\nvelocities, stellar atmospheric parameters, and precise (~0.1 dex) chemical\nabundances for about 15 chemical species. Here we describe the basic APOGEE\ndata reduction software that reduces multiple 3D raw data cubes into\ncalibrated, well-sampled, combined 1D spectra, as implemented for the\nSDSS-III/APOGEE data releases (DR10, DR11 and DR12). The processing of the\nnear-IR spectral data of APOGEE presents some challenges for reduction,\nincluding automated sky subtraction and telluric correction over a 3 degree\ndiameter field and the combination of spectrally dithered spectra. We also\ndiscuss areas for future improvement.\n