Wide-field 12CO (J = 1-0) Imaging of the Nearby Barred Galaxy M83 with
  NMA and Nobeyema 45-m telescope: Molecular Gas Kinematics and Star Formation
  Along the Bar
  We present the results of the wide-field $^{12}$CO (1--0) observations of the
nearby barred galaxy M83 carried out with the Nobeyama Millimeter Array (NMA).
The interferometric data are combined with the data obtained with the Nobeyama
45-m telescope to recover the total-flux. The target fields of the observations
cover the molecular bar and part of the spiral arms, with a spatial resolution
of ~110 pc x 260 pc. By exploiting the resolution and sensitivity to extended
CO emission, the impact of the galactic structures on the molecular gas content
is investigated in terms of the gas kinematics and the star formation. By
inspecting the gas kinematics, the pattern speed of the bar is estimated to be
57.4 $\pm$ 2.8 km s$^{-1}$ kpc$^{-1}$, which places the corotation radius to be
about 1.7 times the semi-major radius of the bar. Within the observed field,
HII regions brighter than 10$^{37.6}$ erg s$^{-1}$ in H{\alpha} luminosity are
found to be preferentially located downstream of the CO emitting regions.
Azimuthal angular offsets between molecular gas and star forming (SF)
calculated with the angular cross-correlation method confirm the trend. By
comparing with a cloud orbit model based on the derived pattern speed, the
angular offsets are found to be in accordance with a time delay of about 10
Myr. Finally, to test whether the arm/bar promote star formation efficiency
(SFE $\equiv$ Star Formation Rate (SFR)/H$_2$ mass), SFR is derived with the
diffuse-background-subtracted H{alpha} and 24{\mu}m images. The arm-to-interarm
ratio of the SFE is found to lie in the range of 2 to 5, while it is ~1 if no
background-removal is performed. The CO-SF offsets and the enhancement of the
SFE in the arm/bar found in the inner region of M83 are in agreement with the
predictions of the classical galactic shock model.
