The DiskMass Survey. I. Overview
  We present a survey of the mass surface-density of spiral disks, motivated by
outstanding uncertainties in rotation-curve decompositions. Our method exploits
integral-field spectroscopy to measure stellar and gas kinematics in nearly
face-on galaxies sampled at 515, 660, and 860 nm, using the custom-built
SparsePak and PPak instruments. A two-tiered sample, selected from the UGC,
includes 146 nearly face-on galaxies, with B<14.7 and disk scale-lengths
between 10 and 20 arcsec, for which we have obtained H-alpha velocity-fields;
and a representative 46-galaxy subset for which we have obtained stellar
velocities and velocity dispersions. Based on re-calibration of extant
photometric and spectroscopic data, we show these galaxies span factors of 100
in L(K) (0.03 < L/L(K)* < 3), 8 in L(B)/L(K), 10 in R-band disk central
surface-brightness, with distances between 15 and 200 Mpc. The survey is
augmented by 4-70 micron Spitzer IRAC and MIPS photometry, ground-based
UBVRIJHK photometry, and HI aperture-synthesis imaging. We outline the
spectroscopic analysis protocol for deriving precise and accurate line-of-sight
stellar velocity dispersions. Our key measurement is the dynamical disk-mass
surface-density. Star-formation rates and kinematic and photometric regularity
of galaxy disks are also central products of the study. The survey is designed
to yield random and systematic errors small enough (i) to confirm or disprove
the maximum-disk hypothesis for intermediate-type disk galaxies, (ii) to
provide an absolute calibration of the stellar mass-to-light ratio well below
uncertainties in present-day stellar-population synthesis models, and (iii) to
make significant progress in defining the shape of dark halos in the inner
regions of disk galaxies.
