I assume it is a homework question...
You may want to into the concept of blackbody radiation, as an explanation. It is discussed in most PChem / Quantum Chem books in the first chapters. Feel free to update your question according to.
Generally, we do not say that photons are excited. Photons do not have ground and excited states in the same chemical sense as electrons. Excited states (of e.g. electron) may emit photons during de-excitation, but those are the excited state of the electron (before the photon even existed) not the photon.
Also, we generally do not say photon decay: technically you can argue that absorption is something like that, but it is definitely not a common way to phrase it, and obviously absorption is absorption, so it will not emit any radiation.
Note: After this answer, the question was changed to talk about electronic excitation instead of "photonic excitations", therefore a large part of my answer is irrelevant.