[Telepathic Intruder]

Apparently it is absorbing x-rays and re-emitting them as black body radiation. The temperature is based on the wavelenth.
I would think that only the missing matter in galactic halos are hot, and the "fillaments" between galaxies cooler. According to the simulations its like a big cobweb, with galaxies forming at the intersections.

[Pontiac]

Apparently it is absorbing x-rays and re-emitting them as black body radiation. The temperature is based on the wavelenth.

Are you saying that the heat does not really exist?

What could be generating that much X-ray radiation to cause that much heat? A Blackhole?

[TigersEye]

That bottom picture looks just like an illustration of the synaptic connections in the brain.