Evidence for dense gas heated by the explosion in Orion KL
  We mapped the kinetic temperature structure of Orion KL in a $\sim$20$''$
($\sim$8000 AU) sized region with para-H$_{2}$CS $7_{07}-6_{06}$,
$7_{26}-6_{25}$, and $7_{25}-6_{24}$ making use of ALMA Band 6 Science
Verification data. The kinetic temperatures obtained with a resolution of
$1\hbox{$\,.\!\!^{\prime\prime}$}65$$\times$$1\hbox{$\,.\!\!^{\prime\prime}$}14$
($\sim$550 AU) are deduced by modeling the measured averaged
velocity-integrated intensity ratios of para-H$_2$CS
$7_{26}-6_{25}/7_{07}-6_{06}$ and $7_{25}-6_{24}/7_{07}-6_{06}$ with a RADEX
non-LTE model. The kinetic temperatures of the dense gas, derived from the
para-H$_2$CS line ratios at a spatial density of 10$^7$ cm$^{-3}$, are high,
ranging from 43 to $>$500 K with an unweighted average of $\sim$170 K. There is
no evidence for internal sources playing an important role in the heating of
the various structures identified in previous work, namely the elongated ridge,
the northwestern clump, and the eastern region of the compact ridge, while the
high temperatures in the western region of the compact ridge may be dominated
by internal massive star formation. Significant gradients of kinetic
temperature along molecular filaments traced by H$_2$CS indicate that the dense
gas is heated by the shocks induced by the enigmatic explosive event, which
occurred several hundred years ago greatly affecting the energetics of the
Orion KL region. Thus, with the notable exception of the western region of the
compact ridge, the high temperatures of the dense gas in Orion KL are probably
caused by shocks from the explosive event, leading to a dominant component of
externally heated dense gas.
