Large Scale Structure Reconstruction with Short-Wavelength Modes

Understand

Large scale density modes are difficult to measure because they are sensitive to systematic observational errors in galaxy surveys, but we can study them indirectly by observing their impact on small scale perturbations.

• Cosmological perturbation theory predicts that second-order density inhomogeneities are a convolution of a short- and a long-wavelength mode.
• This arises physically because small scale structures grow at different rates depending on the large scale environment in which they reside.
• This induces an off-diagonal term in the two-point statistics in Fourier space that we use as the basis for a quadratic estimator for the large scale field.