The ALMA view of W33A: A Spiral Filament Feeding the Candidate Disc in
  MM1-Main
  We targeted the massive star forming region W33A using the Atacama Large
Sub/Millimeter Array (ALMA) in band 6 (230 GHz) and 7 (345 GHz) to search for a
sub-1000au disc around the central O-type massive young stellar object (MYSO)
W33A MM1-Main. Our data achieves a resolution of ~0.2" (~500au) and resolves
the central core, MM1, into multiple components and reveals complex and
filamentary structures. There is strong molecular line emission covering the
entire MM1 region. The kinematic signatures are inconsistent with only
Keplerian rotation although we propose that the shift in the emission line
centroids within ~1000au of MM1-Main could hint at an underlying compact disc
with Keplerian rotation. We cannot however rule out the possibility of an
unresolved binary or multiple system. A putative smaller disc could be fed by
the large scale spiral `feeding filament' we detect in both gas and dust
emission. We also discuss the nature of the now-resolved continuum sources.
