Abstract
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 2016 August, contained APOGEE data for roughly 150,000 stars, and DR14, released in 2017 August, 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 analyses 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 itself).
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Footnotes
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In fact, the APOGEE analysis pipeline is concluded to be not very precise for SG stars with extreme "non-standard" abundance patterns in Section 4.2.
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Available at http://github.com/callendeprieto/ferre.
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Evaluating the ASPCAP performance in the uncalibrated regime of the FGK-dwarfs by comparing to reference samples containing a high degree of such stars will be performed in the future (J. Teske et al. 2018, in preparation).
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