APOGEE-2

APO Galaxy Evolution Experiment 2
APOGEE-2 extends the sky coverage of the SDSS by using telescopes at both Apache Point Observatory (APOGEE-2N) and Las Campanas Observatory in Chile (APOGEE-2S). Using telescopes in both hemispheres means that APOGEE-2 is able to view the entire Milky Way. <i>Image credit: Dana Berry / SkyWorks Digital Inc. and the SDSS collaboration.</i>
APOGEE-2 extends the sky coverage of the SDSS by using telescopes at both Apache Point Observatory (APOGEE-2N) and Las Campanas Observatory in Chile (APOGEE-2S). Using telescopes in both hemispheres means that APOGEE-2 is able to view the entire Milky Way. Image credit: Dana Berry / SkyWorks Digital Inc. and the SDSS collaboration.

The second generation of the Apache Point Observatory Galaxy Evolution Experiment (APOGEE-2) observes the "archaeological" record embedded in hundreds of thousands of stars to explore the assembly history and evolution of the Milky Way Galaxy. The details as to how the Galaxy evolved are preserved today in the motions and chemical compositions of its stars. APOGEE-2 maps the dynamical and chemical patterns of Milky Way stars with data from the 1-meter NMSU Telescope and the 2.5-meter Sloan Foundation Telescope at the Apache Point Observatory in New Mexico (APOGEE-2N), and the 2.5-meter du Pont Telescope at Las Campanas Observatory in Chile (APOGEE-2S).

Key Science Questions

  • What is the history of star formation and chemical enrichment of the Milky Way?
  • What are the dynamics of the disk, bulge, and halo of the Milky Way?
  • What is the age distribution of stars in the Milky Way?
  • Do planet-hosting stars have different properties than stars that have no planets?

To answer these science questions, APOGEE-2 relies upon the spectroscopy of stars using near-infrared light, which can penetrate regions obscured by interstellar dust. The APOGEE-2 spectral data provide a comprehensive view of (1) element abundance distributions in Galactic stars and (2) the dynamical motions of stars at various locations throughout the Milky Way. A primer on spectroscopy, especially in the near-infrared, as well some background on the Milky Way Galaxy can be found here.

APOGEE-1 predominantly observed red giant stars distributed across several kiloparsecs of the Milky Way disk. APOGEE-2 continues to observe these evolved stars and with the Southern hemisphere component, extends into previously unreachable parts of the disk. APOGEE also acquires spectra of young stars and star-forming regions, variable stars, stars in clusters and satellite galaxies, and stars with asteroseismic measurements. See APOGEE Targeting Information for more details.

The APOGEE-2 Survey Area
The APOGEE-2 survey footprint, overlaid on an infrared image of the Milky Way. Each dot shows a position where APOGEE obtains at least 250 stellar spectra. Image credit: P. M. Frinchaboy and SDSS/APOGEE, 2MASS (background image)

APOGEE-2 Technical Details

  • Bright-time observations at APO and LCO
  • Duration: Fall 2014 - Fall 2020
  • Fiber Complement: 300 fibers per 7 deg2 plate (APO 2.5-m) or 3.5 deg2 plate (LCO 2.5-m), or 10 fiber (APO 1-m)
  • Wavelength Range: 1.51-1.70 μm
  • Spectral Resolution: R~22,500
  • DR15 Sample Size: ~263,000 stars
  • Signal-to-Noise Goal: S/N > 100 per pixel
  • Radial Velocity Precision: ~200 m/s
  • Element Abundance Precision: ~0.1 dex for 20 calibrated species

People

Principal Investigator
Steve Majewski (UVa)
Survey Scientist
Jon Holtzman (NMSU)
Project Manager
Jennifer Sobeck (UW)
Previously: Fred Hearty (Penn State)
Instrument Scientist
John Wilson (UVa)
Pipeline Coordinator
Matthew Shetrone (McDonald Observatory)
Target Selection Coordinators
North: Ryan J. Oelkers (Vanderbilt); South: Felipe Antonio Santana Rojas (Universidad de Chile); Special Targets & External Programs: Kevin Covey (WWU)
Survey Operations Scientists
North: Nathan De Lee (Northern Kentucky University); South: Penélope Longa-Peña (Universidad de Antofagasta)
LCO Operations Manager
Christian Nitschelm (Universidad de Antofagasta)
There is also a large team of other people who work to develop pipelines, improve targeting strategies, maintain the instrument, and document the data, among many other tasks.