Science with an ngVLA: Organics in Disk Midplanes with the ngVLA
  Planets assemble in the midplanes of protoplanetary disks. The compositions
of dust and gas in the disk midplane region determine the compositions of
nascent planets, including their chemical hospitality to life. In this context,
the distributions of volatile organic material across the planet and comet
forming zones is of special interest. These are difficult to access in the disk
midplane at IR and even millimeter wavelengths due to dust opacity, which can
veil the midplane, low intrinsic molecular abundances due to efficient
freeze-out, and, in the case of mid-sized organics, a mismatch between expected
excitation temperatures and accessible line upper energy levels. At ngVLA
wavelengths, the dust is optically thin, enabling observations into the planet
forming disk midplane. ngVLA also has the requisite sensitivity. Using TW Hya
as a case study, we show that ngVLA will be able to map out the distributions
of diagnostic organics, such as CH3CN, in nearby protoplanetary disks.
