ALMA Observations of Giant Molecular Clouds in M33 III: Spatially
  Resolved Features of the Star-Formation Inactive Million-solar-mass Cloud
  We present $^{12}$CO ($J$ = 2-1), $^{13}$CO ($J$ = 2-1), and C$^{18}$O ($J$ =
2-1) observations toward GMC-8, one of the most massive giant molecular clouds
(GMCs) in M33 using ALMA with an angular resolution of 0".44 $\times$ 0".27
($\sim$2 pc $\times$ 1pc). The earlier studies revealed that its high-mass star
formation is inactive in spite of a sufficient molecular reservoir with the
total mass of $\sim$10$^{6}$ $M_{\odot}$.
  The high-angular resolution data enable us to resolve this peculiar source
down to a molecular clump scale. One of the GMC's remarkable features is that a
round-shaped gas structure (the "Main cloud" ) extends over $\sim$50 pc scale,
which is quite different from the other two active star-forming GMCs dominated
by remarkable filaments/shells obtained by our series of studies in M33. The
fraction of the relatively dense gas traced by the $^{13}$CO data with respect
to the total molecular mass is only $\sim$2 %, suggesting that their spatial
structure and the density are not well developed to reach an active star
formation. The CO velocity analysis shows that the GMC is composed of a single
component as a whole, but we found some local velocity fluctuations in the Main
cloud and extra blueshifted components at the outer regions. Comparing the CO
with previously published large-scale H I data, we suggest that an external
atomic gas flow supplied a sufficient amount of material to grow the GMC up to
$\sim$10$^6$ $M_{\odot}$.
