High-resolution molecular gas maps of M33

New observations of CO(J = 1 -> 0) line emission from M33, using the 25 element BEARS focal plane array at the Nobeyama Radio Observatory 45 m telescope, in conjunction with existing maps from the BIMA interferometer and the FCRAO 14 m telescope, give the highest resolution (13 '') and most sensitive (sigma(rms) similar to 60mK) maps to date of the distribution of molecular gas in the central 5.5 kpc of the galaxy. A new catalog of giant molecular clouds ( GMCs) has a completeness limit of 1: 3; 10(5) M-circle dot. The fraction of molecular gas found in GMCs is a strong function of radius in the galaxy, declining from 60% in the center to 20% at galactocentric radius R-gal approximate to 4 kpc. Beyond that radius, GMCs are nearly absent, although molecular gas exists. Most (90%) of the emission from low-mass clouds is found within 100 pc projected separation of a GMC. In an annulus 2: 1 kpc < R-gal < 4: 1 kpc, GMC masses follow a power-law distribution with index - 2.1. Inside that radius, the mass distribution is truncated, and clouds more massive than 8; 10(5) M-circle dot are absent. The cloud mass distribution shows no significant difference in the grand-design spiral arms versus the interarm region. The CO surface brightness ratio for the arm to interarm regions is 1.5, typical of other flocculent galaxies.