  We present high-fidelity CO(1-0) imaging of molecular gas across the full
star-forming disk of M83, using ALMA's 12m, 7m, and TP arrays and the MIRIAD
package. The data have a mass sensitivity and resolution of 10^4Msun and 40 pc.
The full disk coverage shows that the characteristics of molecular gas change
radially from the center to outer disk. The molecular gas distribution shows
coherent large-scale structures in the inner part, including the central
concentration, bar offset ridges, and prominent molecular spiral arms. In the
outer disk, the spiral arms appear less spatially coherent, and even
flocculent. Massive filamentary gas concentrations are abundant even in the
interarm regions. Building up these structures in the interarm regions would
require a very long time (~>100Myr). Instead, they must have formed within
stellar spiral arms and been released into the interarm regions. For such
structures to survive through the dynamical processes, the lifetimes of these
structures and their constituent molecules and molecular clouds must be long
(~>100Myr). These interarm structures host little or no star formation traced
by Halpha. The new map also shows extended CO emission, which likely represents
an ensemble of unresolved molecular clouds.
