The Thirteenth Data Release of the Sloan Digital Sky Survey: First
  Spectroscopic Data from the SDSS-IV Survey MApping Nearby Galaxies at Apache
  Point Observatory
  The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) began
observations in July 2014. It pursues three core programs: APOGEE-2, MaNGA, and
eBOSS. In addition, eBOSS contains two major subprograms: TDSS and SPIDERS.
This paper describes the first data release from SDSS-IV, Data Release 13
(DR13), which contains new data, reanalysis of existing data sets and, like all
SDSS data releases, is inclusive of previously released data. DR13 makes
publicly available 1390 spatially resolved integral field unit observations of
nearby galaxies from MaNGA, the first data released from this survey. It
includes new observations from eBOSS, completing SEQUELS. In addition to
targeting galaxies and quasars, SEQUELS also targeted variability-selected
objects from TDSS and X-ray selected objects from SPIDERS. DR13 includes new
reductions of the SDSS-III BOSS data, improving the spectrophotometric
calibration and redshift classification. DR13 releases new reductions of the
APOGEE-1 data from SDSS-III, with abundances of elements not previously
included and improved stellar parameters for dwarf stars and cooler stars. For
the SDSS imaging data, DR13 provides new, more robust and precise photometric
calibrations. Several value-added catalogs are being released in tandem with
DR13, in particular target catalogs relevant for eBOSS, TDSS, and SPIDERS, and
an updated red-clump catalog for APOGEE. This paper describes the location and
format of the data now publicly available, as well as providing references to
the important technical papers that describe the targeting, observing, and data
reduction. The SDSS website, http://www.sdss.org, provides links to the data,
tutorials and examples of data access, and extensive documentation of the
reduction and analysis procedures. DR13 is the first of a scheduled set that
will contain new data and analyses from the planned ~6-year operations of
SDSS-IV.
