APOGEE Data Releases 13 and 14: Data and Analysis

TL;DR

This paper details the data processing, calibration, and analysis methods for SDSS/APOGEE Data Releases 13 and 14, including improvements, known issues, and the integration of a data-driven technique called The Cannon for stellar parameter and chemical abundance determination.

Contribution

It introduces updated analysis methodologies for DR13 and DR14, compares The Cannon with ASPCAP, and discusses the impact of spectral region restrictions on abundance results.

Findings

Improved handling of telluric absorption and persistence.

Inclusion of The Cannon results alongside ASPCAP.

Differences in elemental abundances depending on spectral region analysis.

Abstract

Data and analysis methodology used for the SDSS/APOGEE Data Releases 13 and 14 are described, highlighting differences from the DR12 analysis presented in Holtzman (2015). Some improvement in the handling of telluric absorption and persistence is demonstrated. The derivation and calibration of stellar parameters, chemical abundances, and respective uncertainties are described, along with the ranges over which calibration was performed. Some known issues with the public data related to the calibration of the effective temperatures (DR13), surface gravity (DR13 and DR14), and C and N abundances for dwarfs (DR13 and DR14) are highlighted. We discuss how results from a data-driven technique, The Cannon (Casey 2016), are included in DR14, and compare those with results from the APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP). We describe how using The Cannon in a mode that restricts the abundance analysis of each element to regions of the spectrum with known features from that element leads to Cannon abundances can lead to significantly different results for some elements than when all regions of the spectrum are used to derive abundances.