The MOSDEF Survey: Dynamical and Baryonic Masses and Kinematic
  Structures of Star-Forming Galaxies at $1.4 \leq z \leq 2.6$
  We present H$\alpha$ gas kinematics for 178 star-forming galaxies at z~2 from
the MOSFIRE Deep Evolution Field survey. We have developed models to interpret
the kinematic measurements from fixed-angle multi-object spectroscopy, using
structural parameters derived from CANDELS HST/F160W imaging. For 35 galaxies
we measure resolved rotation with a median $(V/\sigma_{V,0})_{R_E}=2.1$. We
derive dynamical masses from the kinematics and sizes and compare them to
baryonic masses, with gas masses estimated from dust-corrected H$\alpha$ star
formation rates (SFRs) and the Kennicutt-Schmidt relation. When assuming that
galaxies with and without observed rotation have the same median
$(V/\sigma_{V,0})_{R_E}$, we find good agreement between the dynamical and
baryonic masses, with a scatter of $\sigma_{RMS}=0.34$dex and a median offset
of $\Delta\log_{10}M=0.04$dex. This comparison implies a low dark matter
fraction (8% within an effective radius) for a Chabrier initial mass function
(IMF), and disfavors a Salpeter IMF. Moreover, the requirement that
$M_{dyn}/M_{baryon}$ should be independent of inclination yields a median value
of $(V/\sigma_{V,0})_{R_E}=2.1$ for galaxies without observed rotation. If
instead we treat the galaxies without detected rotation as early-type galaxies,
the masses are also in reasonable agreement ($\Delta\log_{10}M=-0.07$dex,
$\sigma_{RMS}=0.37$dex). The inclusion of gas masses is critical in this
comparison; if gas masses are excluded there is an increasing trend of
$M_{dyn}/M_{*}$ with higher specific SFR (SSFR). Furthermore, we find
indications that $V/\sigma$ decreases with increasing H$\alpha$ SSFR for our
full sample, which may reflect disk settling. We also study the Tully-Fisher
relation and find that at fixed stellar mass
$S_{0.5}=(0.5V_{2.2}^2+\sigma_{V,0}^2)^{1/2}$ was higher at earlier times. At
fixed baryonic mass, we observe the opposite trend. [abridged]
