DR12 includes data for ~163,000 APOGEE targets. This includes 146,000 science targets, located in distinct types of survey fields:
~15,000 stars in Bulge fields
~28,000 stars in Halo fields
~55,000 stars in Disk fields
~14,000 stars in Kepler/CoRoT fields
~8,000 objects in Ancillary Science fields
~1,800 stars in Halo Stream fields
~1,200 stars in Sagittarius dSph fields
~8,000 stars in Star Cluster fields
~900 bright stars observed with the NMSU 1m telescope + APOGEE, including bright standards
The APOGEE main survey sample also includes ~17,000 hot stars used for telluric correction, across all field types.
Data Release 12 is the second spectroscopic release from the Apache Point Observatory Galactic Evolution Experiment (APOGEE). DR12 includes spectra, derived stellar parameters, as well as elemental abundances for more than 100,000 stars sampling all major components of the Milky Way. By operating in the infrared (H-band) portion of the electromagnetic spectrum, APOGEE is better able to detect light from stars lying in dusty regions of the Milky Way than surveys conducted in the optical, which makes this survey particularly well-suited for exploring the Galactic disk and bulge.
APOGEE’s high resolution spectra provide detailed information about the properties of individual stars. DR12 provides APOGEE’s processed infrared spectra, as well as catalogs of radial velocities, stellar parameters, and abundances derived from these spectra. DR12 provides, for the first time, APOGEE abundance measurements of 15 individual elements: C, N, O, Na, Mg, Al, Si, S, K, Ca, Ti, V, Mn, Fe, Ni.
DR12 Scope and Status
The APOGEE survey started in September 2011, and DR12 includes all APOGEE observations through July 2014 (encompassing all of SDSS-III). By design, spectra for most of the survey stars are integrated over multiple visits, with at least one visit separated by at least one month, to enable the identification of binary stars through detection of radial velocity variations. In DR12, data for all stars observed during the project will be released, including 12,000 targets observed while commissioning the APOGEE spectrograph (most of these objects were reobserved with the spectrograph in its final, SDSS-III survey configuration). DR12 also includes spectra of ~900 stars that were obtained using the NMSU 1m telescope at Apache Point Obsevatory, using a fiber link to the APOGEE instrument. This allowed observations of brighter stars, including several types of calibration objects.
Several interfaces are available to access the data:
Catalog Archive Server (CAS)
APOGEE target information and derived radial velocities, stellar parameters, and abundances are loaded into the Catalog Archive Server (CAS) database. This contains a number of ways of interfacing with the database, including low-level SQL access through the CasJobs interface that allows you to save and analyze all your search results.
Science Archive Server (SAS)
Summary FITS files containing the derived radial velocities, stellar parameters, and abundances for all APOGEE stars, as well as all raw and processed APOGEE data are available from the Science Archive Server (SAS). A web interface allows users to retrieve spectra for either individual objects or in bulk.
The SkyServer Quick Look tool provides a quick way to find APOGEE spectra for a desired object. Quick Look shows an image and spectrum for all sky objects for which the SDSS has measured a spectrum. The tool also shows the object’s radial velocity and derived stellar atmospheric parameters, and gives links to further data, including the spectrum as a FITS file.
All APOGEE catalog data are available through the search tools of SkyServer. The Spectroscopic Query Form lets you search for spectroscopic catalog objects by position, spectral classification, redshift, and other constraints in spectroscopy and/or imaging. SQL Search lets you create your own search; see the SkyServer SQL Tutorial to learn how to write SQL queries.
Broadly speaking, the main APOGEE data products released in DR12 are the outputs of two software pipelines. The data reduction pipeline delivers extracted, 1-dimensional, calibrated spectra as well as derived radial velocity information. Those interested in working with APOGEE spectra should be aware of instrumental and reduction-specific features visible in the data. Users of the released spectra are strongly advised to visit the Using APOGEE Spectra page. The APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP) determines stellar parameters and 15 elemental abundances through the automatic analysis of APOGEE’s high-resolution H-band spectra. ASPCAP delivers derived effective temperatures (Teff), gravities (log g), and 15 chemical abundances. Users interested in working with ASPCAP data are strongly advised to read the documentation in the Using APOGEE Stellar Parameters page and the Using APOGEE Chemical Abundances page, where uncertainties, potential systematic effects, and other important issues are discussed.
Detailed APOGEE Information
The following pages describe detailed information about various aspects of APOGEE.
- The APOGEE instrument and survey
- gives an overview of how APOGEE spectroscopic data are taken and organized.
- Parameter Catalogs
- describes the APOGEE information that is stored within the CAS database and summary data files and how it can be used. This includes some examples of how to query the database or summary data files to select out different pieces of information for different types of targets.
- APOGEE Data Access
- describes all of the APOGEE data products that are available through the Science Archive Server.
- Using APOGEE Stellar Parameters
- describes important things you need to know if you plan to use the derived stellar atmospheric parameters.
- Using APOGEE Chemical Abundances
- describes important things you need to know if you plan to use the derived elemental abundances.
- Using APOGEE Spectra
- describes some important features in APOGEE spectra about which anyone looking at spectra should be aware.
Detailed APOGEE Software Pipeline Steps
The following pages describe the steps in the APOGEE software pipelines, and the files created at each step.
- APOGEE Target Information
- describes the way in which APOGEE targets are chosen (targeted), and how this is documented in the target flags.
- APOGEE Visit Spectra Reduction
- gives information about how individual visit spectra are observed, processed and stored.
- APOGEE Visit Spectra Combination
- gives information about how the combined spectra for each star are created and stored, including information about the derivation of radial velocities.
- APOGEE Stellar Parameter and Abundance Determination
- describes how the stellar parameters and abundances available in APOGEE spectroscopic catalogs are derived.
- APOGEE Caveats
- is a running list of known issues with the DR12 release.
These web pages attempt to describe the key features in APOGEE data, but they must necessarily be somewhat concise. For the most in-depth discussion of the APOGEE survey and data analysis, users should consult the APOGEE technical papers, which include:
- The APOGEE overview paper
- (Majewski et al. 2015, in prep) discusses the scientific motivation for the survey, as well as the survey requirements and the choice of survey field placements that are implied. It describes survey operations. It summarizes the level to which requirements are met. It references the data releases. It introduces the follow-on, APOGEE-2 survey.
- The APOGEE data paper
- (Holtzman et al. 2015, in prep) presents the final SDSS-III/APOGEE data. It discusses the calibration of the stellar parameters and abundances, and validation of these relative to independent measurements. It also presents the methods by which APOGEE data can be accessed, and discusses some details of the files and databases, including important information to users about what quantities are stored where, uncertainties, and potential issues.
- The APOGEE instrument paper
- (Wilson et al. 2015, in prep) discusses the technical details of the instrument itself, and presents some low level instrument performance data.
- The APOGEE target selection paper
- (Zasowski et al. 2013) discusses the target selection for main survey and APOGEE-1 ancillary science projects. An expanded discussion of the Kepler field targeting can be found in Pinsoneault et al. 2014.
- The APOGEE data reduction paper
- (Nidever et al. 2015, in prep) discusses the data reduction pipeline, describing how the raw data are analyzed to produce reduced, calibrated spectra. It also presents additional instrument performance data (flats, darks, LSF, persistence, etc.), It also discusses the measurement of radial velocities and their quality.
- The APOGEE/ASPCAP paper
- (Garcia Perez et al. 2015, in prep) presents an outline of how the spectra are processed and analyzed to produce stellar parameters and abundances. It demonstrates validation of the overall method using recovery of parameters/abundances from simulated data, and discusses uncertainties that are introduced by real-world issues: S/N, issues related computational efficiency, variation and uncertainty of the LSF, and issues involving the loss of information under sky lines. It present some basic tests of the methodology from very high resolution observations of some well-studied stars (FTS stars).
- The APOGEE linelist paper
- (Shetrone et al. 2015, in prep) presents the details of how the H-band linelists, a critical component for ASPCAP, were developed.
- The APOGEE linelists are tested using high-resolution IR spectra of several well-studied stars in Smith et al. (2013).
- Further tests of the individual elements derived from the ASPCAP pipeline are found in Cunha et al. (2015).
- The APOGEE model atmospheres paper
- (Meszaros et al. 2012) discusses details of the model atmospheres that were used for the final APOGEE-1 (DR12) analysis.
- The APOGEE spectral grids paper
- (Zamora et al. 2015, in prep) presents how the spectral synthesis was done, documents the libraries that have been used, and investigates the sensitivity of the result to the choice of synthesis code and model atmospheres.
- The APOGEE DR10 calibration paper
- (Meszaros et al. 2013) discusses calibration of stellar parameters that were released in DR10. It is superceded by the APOGEE data paper.
Additional technical papers on APOGEE may be forthcoming.