The Integrated Sachs Wolfe effect: unWISE and Planck constraints on Dynamical Dark Energy

Understand

CMB photons redshift and blueshift as they move through gravitational potentials $\Phi$ while propagating across the Universe.

• If the potential is not constant in time, the photons will pick up a net redshift or blueshift, known as the Integrated Sachs-Wolfe (ISW) effect.
• In the $z \ll 1000$ universe, $\dot{\Phi}$ is nonzero on large scales when the Universe transitions from matter to dark energy domination.
• This effect is only detectable in cross-correlation with large-scale structure at $z \sim 1$.