APOGEE Data Releases 13 and 14: Stellar Parameter and Abundance
  Comparisons With Independent Analyses
  Data from the SDSS-IV / Apache Point Observatory Galactic Evolution
Experiment (APOGEE-2) have been released as part of SDSS Data Releases 13
(DR13) and 14 (DR14). These include high resolution H-band spectra, radial
velocities, and derived stellar parameters and abundances. DR13, released in
August 2016, contained APOGEE data for roughly 150,000 stars, and DR14,
released in August 2017, added about 110,000 more. Stellar parameters and
abundances have been derived with an automated pipeline, the APOGEE Stellar
Parameter and Chemical Abundance Pipeline (ASPCAP). We evaluate the performance
of this pipeline by comparing the derived stellar parameters and abundances to
those inferred from optical spectra and analysis for several hundred stars. For
most elements -- C, Na, Mg, Al, Si, S, Ca, Cr, Mn, Ni -- the DR14 ASPCAP
analysis have systematic differences with the comparisons samples of less than
0.05 dex (median), and random differences of less than 0.15 dex (standard
deviation). These differences are a combination of the uncertainties in both
the comparison samples as well as the ASPCAP-analysis. Compared to the
references, magnesium is the most accurate alpha-element derived by ASPCAP, and
shows a very clear thin/thick disk separation, while nickel is the most
accurate iron-peak element (besides iron).
