The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

The Apache Point Observatory Galactic Evolution Experiment (APOGEE), oneof the programs in the Sloan Digital Sky Survey III (SDSS-III), has nowcompleted its systematic, homogeneous spectroscopic survey sampling allmajor populations of the Milky Way. After a three-year observingcampaign on the Sloan 2.5 m Telescope, APOGEE has collected a halfmillion high-resolution (R ˜ 22,500), high signal-to-noise ratio(>100), infrared (1.51-1.70 μm) spectra for 146,000 stars,with time series information via repeat visits to most of these stars.This paper describes the motivations for the survey and its overalldesign—hardware, field placement, target selection,operations—and gives an overview of these aspects as well as thedata reduction, analysis, and products. An index is also given to thecomplement of technical papers that describe various critical surveycomponents in detail. Finally, we discuss the achieved surveyperformance and illustrate the variety of potential uses of the dataproducts by way of a number of science demonstrations, which span fromtime series analysis of stellar spectral variations and radial velocityvariations from stellar companions, to spatial maps of kinematics,metallicity, and abundance patterns across the Galaxy and as a functionof age, to new views of the interstellar medium, the chemistry of starclusters, and the discovery of rare stellar species. As part of SDSS-IIIData Release 12 and later releases, all of the APOGEE data products arepublicly available.