Ways to Access APOGEE Data
This page provides a summary of the available outputs from the different stages of the APOGEE pipelines. These can be obtained via a number of tools.
Quick Links to Data Access
We provide three primary tools to access the APOGEE data: the Science Archive Server (SAS), the Science Archive Webapp (SAW), and the Catalog Archive Server (CAS). File formats are described in the data model and we provide some examples for how to use these resources. However, many users will be satisfied with the final allStar catalog on the SAS, which gives radial velocities, stellar parameters, and abundances for each star, obtained from the combined spectra. Users should consult the "Using APOGEE Data" pages for further instructions on how to properly use and analyze the APOGEE data.
|I want to ...
|APOGEE Quick Links
|Download full files to my computer and write programs to use the data.
|Science Archive Server (SAS)
|The SAS houses parameter summary catalogs, spectra, and all intermediate data products in flat files within a directory structure.
As described in Supplemental Analyses there are multiple file trees in DR17 using different libraries. The default library is synspec with results in the synspec_rev1 filetree.(See Caveat for details)
|Use a Web-based GUI interface to select targets or view spectra.
|Science Archive Webapp (SAW)
|The SAW contains spectra and associated parameters in a searchable interactive interface.
The SAW is loaded from the synspec_rev1 filetree.
|Query a database with SQL to define a sample.
|Catalog Archive Server (CAS)
|The CAS contains the information from the summary catalogs in a queryable database structure that can be accessed through the SkyServer or directly via SQL.
The CAS is loaded from the synspec filetree.
Science Archive Server (SAS)
DR17 does include several "supplemental analyses" for ASPCAP stellar parameters and abundances, for more information on these see the supplementary analysis page .
In the subsections to follow, we describe some of the main data files and explain how to find these in the SAS.
|File Name & Direct Link
|summative catalog containing all quantities for each combined spectrum
| allStar-dr17-synspec_rev1.fits (4.0 Gb)
See also Caveat.
|"lite" summative catalog containing a reduced set of quantities for each combined spectrum
|allStarLite-dr17-synspec_rev1.fits (1.8 Gb)
|summative catalog containing quantities derived from each individual visit spectrum
|allVisit-dr17-synspec_rev1.fits (2.8 Gb)
|catalog of Cannon stellar parameters and abundances
| Not produced in DR17;
Please see DR15 Data Access Documentation for details on how to retrieve these files.
|DR15 Cannon Data Model
Combined ASPCAP Spectrum:: aspcapStar
The pseudo-continuum normalized, combined spectrum, with best matching synthetic ASPCAP spectrum is recorded as one file per object in the aspcapStar file (data model). These are sorted by telescope and field, and can be found in the SAS using a path constructed as follows:
The file name is constructed as:
APOGEE_ID are tags for each object that can be found in the allStar (or equivalent) summary file. Thus, to acquire this file, the user can build the URL from information in the allStar file.
Combined Spectrum:: apStar or asStar
The combined, RV-corrected spectra are recorded as one file per object in the apStar or asStar files, where apStar files are created for objects observed by the northern spectrograph and asStar files are created for objects observed by the southern spectrograph. These are sorted by telescope and field, and can be found in the SAS using a path constructed as follows:
The filename is constructed as:
In the allStar (or equivalent) summary file, the filename for the combined spectrum is contained in the
FILE tag. Thus, the user can build the URL from information contained in the allStar file.
Visit Spectrum:: apVisit or asVisit
The individual visit spectra are recorded as one file per visit in the apVisit or asVisit files. These are sorted by telescope, plate,
FIBERID. These files can be found in the SAS using a path constructed as follows:
The filename is constructed as:
apVisit-dr17-PLATE-MJD-FIBERID.fits or asVisit-dr17-PLATE-MJD-FIBERID.fits
This information can be acquired from the allVisit summary file, or in the VISITS tag of the allStar file. The
VISITS tag contains a comma-separated list of the visit file names (without
Summary Table for Spectral Data
|APOGEE File Name
|Pseudo-continuum normalized, combined spectrum, with best matching synthetic ASPCAP spectrum, one file per object
|Combined spectrum, one file per object
|Individual visit spectrum, one file per visit
Intermediate Data Products
In addition to the summary catalogs and spectral data, all intermediate data products are also provided in the data release. Here the process is presented in the order of operations from targeting to final ASPCAP parameters and abundances. The pipeline code is available on github: sdss/apogee.
Targeting Field Summary Files
DR17 includes four types of files containing useful information on the stars (both targeted and non-targeted) in APOGEE fields and on the fields themselves, the designs, and the plates in which the targets are organized (see further details on this organizational structure in Zasowski et al. 2013 and Zasowski et al. 2017 ).
All summary files can be found in this directory:
|Summary file that contains information for all fields, such as central coordinates
|contains information on the individual designs, or groups of stars, like color limits and cohort fiber allocations
|contains information on the physical plates, such as drill angle
In addition to these summary files, we also have the targeting input files that are used to design each plate. These are organized by survey and by field. They are contained in folders within
/sas/dr17/apogee/target/ and the links provided below go to the proper sub-directory.
|contains photometric and proper motion information on the candidate targets in the APOGEE-2 fields; one file for each field in the survey.
|contains photometric and proper motion information on the candidate targets in the APOGEE-1 fields; one file for each field in the survey.
|contains photometric and proper motion information on the candidate targets in the APOGEE 1m fields; one file for each field in the survey.
|Similar to apogeeObject
APOGEE raw image data are also available on the SAS. These are organized by telescope and
MJD. To find these files, the user needs to have acquired the
MJD for each visit in the allVisit file.
|Location of Files
| Apache Point Observatory
| Las Campanas Observatory
| Apache Point Observatory
The raw data files are named apR-
EXPOSURE.apz for data taken by the northern spectrograph and asR-
EXPOSURE.apz for data taken by the southern spectrograph. The
CHIP can be “a”, “b”, or “c”, where these letters correspond to the “red”, “green”, and “blue” APOGEE detectors, respectively.
ap1D files are available, but users should consult the data models (ap1D and ap2D), as well as the APOGEE reduction paper (Nidever et al. 2015) before using these files.
Visit Level Processing
The visit-level processing occurs in a code called apred and is described on Visit Reduction. These are are organized by telescope,
MJD. The file path is constructed as follows:
|input or output
|the apred processing plan
|calibrated spectra file for each chip of each exposure
|Summary file for all exposures of each chip containing the 300 combined flux- and wavelength-calibrated spectra
|Summary file with metadata for the objects with apPlate/asPlate files
|for a given object on a given plate/MJD the combined flux- and wavelength-calibrated spectra for all exposures
|Summary file with the derived parameters for objects with apVisit/asVisit files (no spectra)
The visit spectra for each target are combined as described on the visit combination page. This occurs in the following directory:
|input or output
|Combined spectrum for an individual object.
|one for each object
|Radial velocities and target information for all stars in a given field
|Table of individual visit RVs for a given field
APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP)
The ASPCAP stellar parameters pipeline produces one intermediate file for each field that is then merged to form the allStar summary file. These “aspcapField” files are found in the aspcap directories sorted by telescope and field.
|input or output
|ASPCAP stellar parameters (logg, Teff, [M/H], etc.), normalized spectrum, and best fit spectrum for each stars in a given field.
DR17 Value Added Catalogs
The following Value Added Catalogs (VACs) are available for the DR17 datasets:
- Open Clusters -- Provides membership analysis for stars in the vicinity of known open clusters
- The Joker -- Provides stellar orbital parameters from modeling multi-epoch RV measurements using The Joker
- SB2 -- Provides spectroscopic binary identifications
- APOGEE NET -- Provides an independent analysis of APOGEE spectra using neural nets
- Red Clump -- Provides a catalog of red clump stars using spectro-photometric selections.
- AstroNN -- Provides stellar parameters, elemental abundances, distances, and ages from a neural network-based code trained on the spectra; orbital parameters are provided using these distances and GalPy.
- StarHorse -- Provides distances and extinctions using spectro-photometry for all stars in DR17
- APOGEE-Centric Fire Simulations -- Provides mock catalogs with APOGEE-error model using the Ananke framework to sample the Latte Simulations
Additional Value Added Catalogs will be made public in 2022.
Catalog Archive Server (CAS)
APOGEE target information and derived radial velocities, stellar parameters, and elemental abundances are loaded into the Catalog Archive Server (CAS) database. CAS contains a number of ways of interfacing with the database, including SQL-based access through the CasJobs portal that allows you to save and analyze all your search results.
The SkyServer Explore tool provides a quick way to find APOGEE spectra for the desired object. The QuickLook pane shows an image and spectrum for each SDSS object. For objects with APOGEE spectra, the tool includes an APOGEE section. The APOGEE section of the Explore tool shows a composite spectrum, radial velocities, and derived stellar atmospheric parameters, while also providing links to additional data, including the spectrum as a FITS file.
All APOGEE catalog data are available through the search tools of SkyServer. The Infrared Spectroscopy Query Form lets you search for APOGEE catalog objects by position, spectral classification, velocity, and other constraints from spectroscopic and/or photometric parameters. SQL Search lets you create your own search using the SQL database programming language; see the SkyServer SQL Tutorial to learn how to write SQL queries.
We provide some use-cases for the CAS tools on Examples.
Science Archive Webapp (SAW)
The Science Archive Webapp (SAW) provides a searchable interface for infrared spectra and includes both an interactive view of the spectra and a data download facility (supports both rsync and wget):
- Infrared Plate Search
- Infrared Spectrum Search
- Infrared Spectrum View Visits
- Infrared Spectrum View Stars
- Infrared Data Access API
The SAW permits some simple object searches as well as interactively plots their associated spectra. It can also be used to construct lists of spectra to be downloaded in bulk; see further instructions in Bulk Data Downloads.
We provide some use-cases for the SAW tools on Examples.
The DR16 release involved a major reorganization of the SAS file structure for APOGEE data that is maintained in DR17. For consistency with previous data releases, we provide the equivalent pipeline versions here. Users wishing to access data from data releases are advised to refer to those pages, e.g., DR15 Data Access.
- APRED_VERSION:: dr17
- APSTAR_VERSION:: stars
- ASPCAP_VERSION:: synspec
- RESULTS_VERSION:: OBSOLETE