Sub-arcsecond Imaging of the Complex Organic Chemistry in Massive
  Star-forming Region G10.6-0.4
  Massive star-forming regions exhibit an extremely rich and diverse chemistry,
which in principle provides a wealth of molecular probes, as well as
laboratories for interstellar prebiotic chemistry. Since the chemical structure
of these sources displays substantial spatial variation among species on small
scales (${\lesssim}10^4$ au), high angular resolution observations are needed
to connect chemical structures to local environments and inform astrochemical
models of massive star formation. To address this, we present ALMA 1.3 mm
observations toward OB cluster-forming region G10.6-0.4 (hereafter "G10.6") at
a resolution of 0.14$^{\prime\prime}$ (700 au). We find highly-structured
emission from complex organic molecules (COMs) throughout the central 20,000
au, including two hot molecular cores and several shells or filaments. We
present spatially-resolved rotational temperature and column density maps for a
large sample of COMs and warm gas tracers. These maps reveal a range of gas
substructure in both O- and N-bearing species. We identify several spatial
correlations that can be explained by existing models of COM formation,
including NH$_2$CHO/HNCO and CH$_3$OCHO/CH$_3$OCH$_3$, but also observe
unexpected distributions and correlations which suggest that our current
understanding of COM formation is far from complete. Importantly, complex
chemistry is observed throughout G10.6, rather than being confined to hot
cores. The COM composition appears to be different in the cores compared to the
more extended structures, which illustrates the importance of high spatial
resolution observations of molecular gas in elucidating the physical and
chemical processes associated with massive star formation.
