Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache
  Point Observatory
  We present an overview of a new integral field spectroscopic survey called
MaNGA (Mapping Nearby Galaxies at Apache Point Observatory), one of three core
programs in the fourth-generation Sloan Digital Sky Survey (SDSS-IV) that began
on 2014 July 1. MaNGA will investigate the internal kinematic structure and
composition of gas and stars in an unprecedented sample of 10,000 nearby
galaxies. We summarize essential characteristics of the instrument and survey
design in the context of MaNGA's key science goals and present prototype
observations to demonstrate MaNGA's scientific potential. MaNGA employs
dithered observations with 17 fiber-bundle integral field units that vary in
diameter from 12" (19 fibers) to 32" (127 fibers). Two dual-channel
spectrographs provide simultaneous wavelength coverage over 3600-10300 A at
R~2000. With a typical integration time of 3 hr, MaNGA reaches a target r-band
signal-to-noise ratio of 4-8 (per A, per 2" fiber) at 23 AB mag per sq. arcsec,
which is typical for the outskirts of MaNGA galaxies. Targets are selected with
stellar mass greater than 1e9 Msun using SDSS-I redshifts and i-band luminosity
to achieve uniform radial coverage in terms of the effective radius, an
approximately flat distribution in stellar mass, and a sample spanning a wide
range of environments. Analysis of our prototype observations demonstrates
MaNGA's ability to probe gas ionization, shed light on recent star formation
and quenching, enable dynamical modeling, decompose constituent components, and
map the composition of stellar populations. MaNGA's spatially resolved spectra
will enable an unprecedented study of the astrophysics of nearby galaxies in
the coming 6 yr.
