  I derive the distribution of energy and momentum transmitted from a fast
parton to a medium of thermalized quarks, or the source term, in perturbative
thermal field theory directly from the quark energy-momentum tensor. The fast
parton is coupled to the medium by adding an interaction term to the
Lagrangian. The thermal expectation value of the energy-momentum tensor source
term is then evaluated using standard Feynman rules at finite temperature. It
is found that local excitations, which are important for exciting an observable
Mach cone structure, fall sharply as a function of the energy of the fast
parton. This may have implications for the trigger $p_T$ dependence of
measurements of azimuthal dihadron particle correlations in heavy-ion
collisions. In particular, a conical emission pattern would be less likely to
be observed for increasing trigger $p_T$. I show that the results presented in
this paper can be generalized to more realistic modeling of fast parton
propagation, such as through a time dependent interaction term, in future
studies.
