Available Infrared Spectroscopic Data from SDSS-III APOGEE

Introduction

Detailed descriptions of the APOGEE pipeline reduction steps are provided on other pages:

Here, we provide a summary of the files associated with the different steps of the pipeline. These tables include links to the file format documentation (the "data model") and templates that can be used to generate SAS URLs for those files. The templates are in "C printf " format, and can be used in C, bash, Python, and many other languages to automatically generate URLs.

Most of the catalog data (but not the spectra themselves) have been loaded into the Catalog Archive Server (CAS) database. Users may be better off obtaining SDSS data through a carefully constructed CAS query than they are downloading the data files from the SAS. Simple queries can be used to select just the objects and parameters of interest, while more complex queries can be used to do complex calculations on many objects, thereby avoiding the need to download the data on them at all.

The major spectroscopic results are contained in a few different file structures (on SAS) and database tables (in CAS), listed below. Note that the links into SAS below bring you into the full directory tree; before perusing that, it may be best to read both Understanding APOGEE Spectroscopic Data and the data model.

Methods for accessing these data are summarized on the data access page.

Reduction Version Numbers

The APOGEE pipeline is likely to continue to be developed, so it may be important to track the version of the pipeline that was used to reduce APOGEE spectra. To allow for changes in different sections of the pipeline without requiring everything to be rerun with any change, four separate version names track the software used in different portions of the pipeline:

APRED_VERS denotes the version of the basic spectra reduction code used to generate the visit spectra.
APSTAR_VERS denotes the version of the code used to combine individual visit spectra into higher signal-to-noise, resampled, combined spectra.
ASPCAP_VERS denotes the version of the code used to determine the stellar atmospheric parameters for each combined spectrum.
RESULTS_VERS denotes the version of the code used to compile the final results, along with applying additional empirical corrections and providing data flag information about data quality, based on evaluation of the results for calibration objects. A given RESULTS_VERS implies versions of all of the preceding steps, and thus uniquely identifies the full set of software used.

APOGEE DR10 uses the following versions:

Version (RESULTS_VERS)	APRED_VERSION	APSTAR_VERSION	ASPCAP_VERSION	Comment
v304	r3	s3	v304	Improves minor bugs in calibrated Teff and external errors

Catalogs of quantities measured from APOGEE spectra

Summary FITS table files of cataloged parameters (not the spectra themselves) are provided in the SAS. These data are also loaded into the CAS to enable database access. Note that one of the FITS table files (allStar) is split into two separate CAS tables: aspcapStar and apogeeStar, and thus listed twice in the table below.

SAS location	CAS table	Description
allStar-RESULTS_VERS.fits (in APOGEE_REDUX; see datamodel)	aspcapStar	Catalog of ASPCAP parameters for observed stars
allStar-RESULTS_VERS.fits (in APOGEE_REDUX; see datamodel)	apogeeStar	Catalog of stellar parameters from combined spectra (e.g., RVs)
allVisit-RESULTS_VERS.fits (in APOGEE_REDUX; see datamodel)	apogeeVisit	Catalog of parameters from individual visit spectra

Spectral data

Spectral data is available in the SAS. Visit spectra are organized by PLATE and MJD. Combined spectra and ASPCAP spectra (which are derived from the combined spectra) are organized by field (encoded by a LOCATION_ID). One way to associate PLATES, LOCATION_ID, and field names is to look at the index embedded in the SAS. You can also get this information from the CAS or the summary data files, see e.g., examples for plates or for location IDs. For downloading a large number of these spectra in a single step, see our bulk data access documentation.

SAS location	SAS interface	Description
aspcapStar-RESULTS_VERS-STARNAME.fits (in APOGEE_REDUX/APRED_VERS/APSTAR_VERS/ASPCAP_VERS/RESULTS_VERS/LOCATION_ID; see datamodel)	aspcapStar-RESULTS_VERS-STARNAME.fits	Pseudo-continuum normalized, combined spectra, with best matching synthetic spectrum, one file per object
apStar-APSTAR_VERS-STARNAME.fits (in APOGEE_REDUX/APRED_VERS/APSTAR_VERS/LOCATION_ID; see datamodel)	apStar-APSTAR_VERS-STARNAME.fits	Combined spectra, one file per object
apVisit-APRED_VERS-PLATE-MJD-FIBER.fits (in APOGEE_REDUX/APRED_VERS/plates/PLATE_ID/MJD5; see datamodel)	apVisit-APRED_VERS-PLATE-MJD-FIBER.fits	Individual spectra, one file per PLATE-MJD-FIBER

Intermediate data products

While most users are likely to be satisfied with the data in the files listed above, there are a number of lower level intermediate processed files which we list here.

APOGEE Raw Data Collection

APOGEE raw data is stored on the SAS. It is probably unlikely that users will want to access this, as the raw data contains all of the up-the-ramp reads (every 10s) for every exposure; its a lot of data!

SAS files generated in spectroscopic data collection
File Type	in/out	Description	URL format	format parameters
Log file	out	records exposures collected on a night	Not public
apR	out	raw spectroscopic data frames	$APOGEE_DATA/%d/apR-%c-%08d.apz	mjd, detector (a,b,or c), exposure id
plPlugMapM	in	records which fiber corresponds to which hole in a plate (and therefore which objects, and what coordinates on the sky)	Not public

APOGEE Visit Processing

For details about the process, see the page on visit reduction and and/or the reduction paper (Nidever et al., in prep)

The apred pipeline reads science and calibration exposures from the spectrographs, reduces and calibrates the science exposures, extracts the one dimensional spectra from the two dimensional exposures, corrects for sky emission and telluric absorption, stacks multiple dithered exposures into well-sampled spectra, and produces corresponding masks and noise estimates.

SAS files used or generated by the apred pipeline
File Type	in/out	Description	URL format	format parameters
apPlan	in	the apred processing plan	$APOGEE_REDUX/APRED_VERS/plates/%d/%05d/apPlan-%04d-%05d.par	plate, mjd, plate, mjd
apCframe	out	calibrated spectra for a single CCD and exposure	$APOGEE_REDUX/APRED_VERS/plates/%04d/%05d/apCframe-%c-%08d.par	plate, mjd, chip (a, b, or c), exposure id
apPlate	out	the 300 combined flux- and wavelength-calibrated spectra over all exposures (potentially spanning multiple nights) for a given mapped plate	$APOGEE_REDUX/APRED_VERS/plates/%s/%04d/apPlate-%04d-%05d.fits	plate, mjd, plate, mjd
apVisit	out	the combined flux- and wavelength-calibrated spectra over all exposures (potentially spanning multiple nights) for a given object on a given plate/MJD	$APOGEE_REDUX/APRED_VERS/plates/%s/%04d/apVisit-%04d-%05d-%03d.fits	plate, mjd, plate, mjd

Stellar Combination Processing (apstar)

For details about the process, see the page on visit combination and and/or the reduction paper (Nidever et al., in prep)

SAS files used or generated by the visit combination pipeline
File Type	in/out	URL format	format parameters
apStar	out	$APOGEE_REDUX/%s/%s/%s/apStar-%s.fits	APRED_VERS, APSTAR_VERS, LOCATION_ID, APOGEE_ID
apField	out	$APOGEE_REDUX/%s/%s/%s/apField-%d.fits	APRED_VERS, APSTAR_VERS, LOCATION_ID
apFieldVisits	out	$APOGEE_REDUX/%s/%s/%s/apFieldVisits-%d.fits	APRED_VERS, APSTAR_VERS, LOCATION_ID

APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP)

References: Garcia-Perez et al, Mezsaros et al., Shetrone et al.

The ASPCAP stellar parameters pipeline produces a number of files, stored together:

SAS files used or generated by the ASPCAP pipeline
File Type	in/out	Description	URL format	format parameters
aspcapField	out	ASPCAP stellar parameters ([M/H], log g, etc.)	$APOGEE_REDUX/%s/%s/%s/%s//aspcapField-%04d.fits	APRED_VERS, APSTAR_VERS, ASPCAP_VERS, RESULTS_VERS, LOCATION_ID
aspcapStar	out	ASPCAP stellar parameters	$APOGEE_REDUX/%s/%s/%s/%s/LOCATION_ID/aspcapStar-%s-%04d.fits	APRED_VERS, APSTAR_VERS, ASPCAP_VERS, RESULTS_VERS, RESULTS_VERS, LOCATION_ID