The distribution of deuterated formaldehyde within Orion-KL
  We report the first high angular resolution imaging (3.4\arcsec $\times$
3.0\arcsec) of deuterated formaldehyde (HDCO) toward Orion--KL, carried out
with the Submillimeter Array (SMA). We find that the spatial distribution of
the formaldehyde emission systematically differs from that of methanol: while
methanol is found towards the inner part of the region, HDCO is found in colder
gas that wraps around the methanol emission on four sides. The HDCO/H$_2$CO
ratios are determined to be 0.003--0.009 within the region, up to an order of
magnitude higher than the D/H measured for methanol. These findings strengthen
the previously suggested hypothesis that there are differences in the chemical
pathways leading to HDCO (via deuterated gas phase chemistry) and deuterated
methanol (through conversion of formaldehyde into methanol on the surface of
icy grain mantles).
