  Colloids with patchy metal coating under laser irradiation could act as local
sources of heat due to the absorption of light. While for asymmetric colloids
this could induce self-propulsion, it also leads to the generation of a slowly
decaying temperature profile that other colloids could interact with. The
collective behavior of a dilute solution of such thermally active particles is
studied using a stochastic formulation. It is found that when the Soret
coefficient is positive, the system could be described in stationary-state by
the nonlinear Poisson-Boltzmann equation and could adopt density profiles with
significant depletion in the middle region when confined. For colloids with
negative Soret coefficient, the system can be described as a dissipative
equivalent of a gravitational system. It is shown that in this case the
thermally active colloidal solution could undergo an instability at a critical
laser intensity, which has similarities to supernova explosion.
