Is the number of energetic CMB Photons (produced due to Sunyaev-Zel'dovich effect) abundant in the whole universe now ?
The Sunyaev–Zel'dovich effect is the distortion of the cosmic microwave background radiation (CMB) by high energy electrons in galaxy clusters, in which the low energy CMB photons receive an average energy boost during collision with the high energy cluster electrons.
Observed distortions of the cosmic microwave background spectrum are used to detect the density perturbations of the universe. Using the Sunyaev–Zel'dovich effect, dense clusters of galaxies have been observed.
So is this effect still in occurence? Is the universe filled abundantly by these photons or they are in a very small amount ?