Target Selection for the SDSS-IV APOGEE-2 Survey

TL;DR

This paper details the target selection process and observational design of the APOGEE-2 survey, which aims to study stellar populations and Galactic evolution through high-resolution infrared spectroscopy of diverse star types across the sky.

Contribution

It introduces the target selection algorithms, observational strategies, and data documentation for the APOGEE-2 survey, expanding on previous work with new target types and instrumentation.

Findings

Targeting a wide variety of stellar types across the sky.

Development of new selection algorithms for diverse targets.

Comprehensive documentation included in SDSS data releases.

Abstract

APOGEE-2 is a high-resolution, near-infrared spectroscopic survey observing roughly 300,000 stars across the entire sky. It is the successor to APOGEE and is part of the Sloan Digital Sky Survey IV (SDSS-IV). APOGEE-2 is expanding upon APOGEE's goals of addressing critical questions of stellar astrophysics, stellar populations, and Galactic chemodynamical evolution using (1) an enhanced set of target types and (2) a second spectrograph at Las Campanas Observatory in Chile. APOGEE-2 is targeting red giant branch (RGB) and red clump (RC) stars, RR Lyrae, low-mass dwarf stars, young stellar objects, and numerous other Milky Way and Local Group sources across the entire sky from both hemispheres. In this paper, we describe the APOGEE-2 observational design, target selection catalogs and algorithms, and the targeting-related documentation included in the SDSS data releases.