On fundamental solutions and Gaussian bounds for degenerate parabolic equations with time-dependent coefficients

We consider second order degenerate parabolic equations with real, measurable, and time-dependent coefficients. We allow for degenerate ellipticity dictated by a spatial $A_2$-weight. We prove the existence of a fundamental solution and derive Gaussian bounds. Our construction is based on the original work of Kato \cite{Kato}.