Mapping physical parameters in Orion KL at high spatial resolution
  The Orion Kleinmann-Low nebula (Orion KL) is notoriously complex and exhibits
a range of physical and chemical components. We conducted high angular
resolution (sub-arcsecond) observations of $^13$CH$_{3}$OH $\nu=0$
($\sim$0.3$^{\prime\prime}$ and $\sim$0.7$^{\prime\prime}$) and CH$_3$CN
$\nu_8=1$ ($\sim$0.2$^{\prime\prime}$ and $\sim$0.9$^{\prime\prime}$) line
emission with the Atacama Large Millimeter/submillimeter Array (ALMA) to
investigate Orion KL's structure on small spatial scales (${\le}350$ au). Gas
kinematics, excitation temperatures, and column densities were derived from the
molecular emission via a pixel-by-pixel spectral line fitting of the image
cubes, enabling us to examine the small-scale variation of these parameters.
Sub-regions of the Hot Core have a higher excitation temperature in a
0.2$^{\prime\prime}$ beam than a 0.9$^{\prime\prime}$ beam, indicative of
possible internal sources of heating. Furthermore, the velocity field includes
a bipolar ${\sim}7{-}8$ km s$^{-1}$ feature with a southeast-northwest
orientation against the surrounding ${\sim}4{-}5$ km s$^{-1}$ velocity field,
which may be due to an outflow. We also find evidence of a possible source of
internal heating toward the Northwest Clump, since the excitation temperature
there is higher in a smaller beam versus a larger beam. Finally, the region
southwest of the Hot Core (Hot Core-SW) presents itself as a particularly
heterogeneous region bridging the Hot Core and Compact Ridge. Additional
studies to identify the (hidden) sources of luminosity and heating within Orion
KL are necessary to better understand the nebula and its chemistry.
