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 \sim 110 pc \times 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 \sim 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 .