Joint velocity and density reconstruction of the Universe with nonlinear differentiable forward modeling

Understand

Reconstructing the initial conditions of the Universe from late-time observations has the potential to optimally extract cosmological information.

• Due to the high dimensionality of the parameter space, a differentiable forward model is needed for convergence, and recent advances have made it possible to perform reconstruction with nonlinear models based on galaxy (or halo) positions.
• In addition to positions, future surveys will provide measurements of galaxies' peculiar velocities through the kinematic Sunyaev-Zel'dovich effect (kSZ), type Ia supernovae, and the fundamental plane or Tully-Fisher relations.
• Here we develop the formalism for including halo velocities, in addition to halo positions, to enhance the reconstruction of the initial conditions.