The evidence for the continuing accretion of gas by the Milky Way involves high-velocity clouds, or HVCs--mysterious clumps of hydrogen, moving rapidly through the outer regions of the galaxy.
High-velocity clouds can be shortened to HVCs.
( z1 possible :ARG1 ( z2 shorten :ARG1 ( z3 cloud :mod ( z4 velocity :ARG1-of ( z5 high ) ) ) :ARG4 ( z6 small-molecule :name ( z7 name :op "HVC" ) ) ) )