During a relatively non-technical astronomy seminar the other day, the speaker displayed the famous WMAP full-sky image as an aid to describing what the CMB is, the scale of its fluctuations, etc. This speaker mentioned that there are correlations between the higher-temperature regions on the map and regions of large-scale galaxy structure seen in deep-sky surveys.
I was surprised to hear this. My understanding is that CMB is an image of events currently about 14 billion light years away, while the observed large-scale filaments of galaxies are at approximately half that distance. I wouldn't have expected any density fluctuation 14 billion light years away to share any correlation with a density fluctuation 7 billion light years away.
When I asked, the speaker admitted to being "mostly a star guy" and continued with his excellent talk.
Is there actually a correlation between the warmer, denser regions of the CMB and the distribution of dense galaxy clusters? Is there a causal reason for these distant objects to be correlated with each other? Is there a lensing effect on the CMB temperature? Or is this "correlation" just an enticing-sounding mistake, slowly working its way into common knowledge?