SEGUE-2 and APOGEE: Revealing the History of the Milky Way

TL;DR

This paper discusses the SEGUE-2 and APOGEE surveys, which aim to map the Milky Way's stellar populations, kinematics, and chemical enrichment patterns using optical and infrared spectroscopy, providing new insights into Galactic history.

Contribution

It introduces two large spectroscopic surveys, SEGUE-2 and APOGEE, with advanced instrumentation to study the Milky Way's formation and evolution in unprecedented detail.

Findings

SEGUE-2 will double the sample of distant halo stars observed in SDSS-II.

APOGEE will provide high-resolution infrared spectra of 100,000 red giants.

Spectroscopic data will enable detailed chemical and kinematic analysis of Galactic populations.

Abstract

The history of the Milky Way is encoded in the spatial distributions, kinematics, and chemical enrichment patterns of its resolved stellar populations. SEGUE-2 and APOGEE, two of the four surveys that comprise SDSS-III (the Sloan Digital Sky Survey III), will map these distributions and enrichment patterns at optical and infrared wavelengths, respectively. Using the existing SDSS spectrographs, SEGUE-2 will obtain spectra of 140,000 stars in selected high-latitude fields to a magnitude limit r ~ 19.5, more than doubling the sample of distant halo stars observed in the SDSS-II survey SEGUE (the Sloan Extension for Galactic Understanding and Exploration). With spectral resolution R ~ 2000 and typical S/N per pixel of 20-25, SEGUE and SEGUE-2 measure radial velocities with typical precision of 5-10 km/s and metallicities ([Fe/H]) with a typical external error of 0.25 dex. APOGEE (the Apache Point Observatory Galactic Evolution Experiment) will use a new, 300-fiber H-band spectrograph (1.5-1.7 micron) to obtain high-resolution (R ~ 24,000), high signal-to-noise ratio (S/N ~ 100 per pixel) spectra of 100,000 red giant stars to a magnitude limit H ~ 12.5. Infrared spectroscopy penetrates the dust that obscures the inner Galaxy from our view, allowing APOGEE to carry out the first large, homogeneous spectroscopic survey of all Galactic stellar populations. APOGEE spectra will allow radial velocity measurements with < 0.5 km/s precision and abundance determinations (with ~ 0.1 dex precision) of 15 chemical elements for each program star, which can be used to reconstruct the history of star formation that produced these elements. (abridged)