CO Multi-line Imaging of Nearby Galaxies (COMING). VII. Fourier
  decomposition of molecular gas velocity fields and bar pattern speed
  The $^{12}$CO $(J=1\rightarrow0)$ velocity fields of a sample of 20 nearby
spiral galaxies, selected from the CO Multi-line Imaging of Nearby Galaxies
(COMING) legacy project of Nobeyama Radio Observatory, have been analyzed by
Fourier decomposition to determine their basic kinematic properties, such as
circular and noncircular velocities. On average, the investigated barred (SAB
and SB) galaxies exhibit a ratio of noncircular to circular velocities of
molecular gas larger by a factor of 1.5-2 than non-barred (SA) spiral galaxies
at radii within the bar semimajor axis $a_\mathrm{b}$ at 1 kpc resolution, with
a maximum at a radius of $R/a_\mathrm{b}\sim0.3$. Residual velocity field
images, created by subtracting model velocity fields from the data, reveal that
this trend is caused by kpc-scale streaming motions of molecular gas in the bar
region. Applying a new method based on radial velocity reversal, we estimated
the corotation radius $R_\mathrm{CR}$ and bar pattern speed $\Omega_\mathrm{b}$
in seven SAB and SB systems. The ratio of the corotation to bar radius is found
to be in a range of $\mathcal{R}\equiv
R_\mathrm{CR}/a_\mathrm{b}\sim0.8\mathrm{-}1.6$, suggesting that intermediate
(SBb-SBc), luminous barred spiral galaxies host fast and slow rotator bars.
Tentative negative correlations are found for $\Omega_\mathrm{b}$ vs.
$a_\mathrm{b}$ and $\Omega_\mathrm{b}$ vs. total stellar mass $M_\ast$,
indicating that bars in massive disks are larger and rotate slower, possibly a
consequence of angular momentum transfer. The kinematic properties of SAB and
SB galaxies, derived from Fourier decomposition, are compared with recent
numerical simulations that incorporate various rotation curve models and galaxy
interactions.
