  The cosmological dynamics of minimally coupled scalar field that couple to
the background matter with thermal interactions is investigated in exponential
potential. The conditions for the existence and stability of various critical
points as well as their cosmological implications are obtained. Although we
show that the effects of thermal interaction such as depressing the
equation-of-state parameter of quintessence, is only important at the early
time, the evolution of equation-of-state parameter of quintessence is
manifested. The upper bound is required on the coupling between quintessence
and relativistic relic particles such as photons and neutrinos.

Astrophysics