Extragalactic lensing sims

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(Marcelo Alvarez writing)


CMB Lensing

Using a 'field+halo' model to generate lensing kappa maps from Gaussian random field (GRF) of density fluctuations on the past light cone.

Halo Model

The peak patch algorithm is run on the GRF to produce a catalog of halos with [RA, Dec, redshift, velocity, mass]. The halos are assumed to have a spherically-symmetric matter distribution parameterized by a generalized NFW density profile (gNFW). This contribution to the convergence from each halo is then projected onto the kappa map, appropriately weighted by the lensing kernel, W(z).

Field Model

(development in progress) Lagrangian perturbation theory is used to move matter not within halos to its final Eulerian position. This field matter distribution is then added directly to the kappa map. A [260 x 260 x 60] Mpc/h slab at z=0 is shown below with all the matter moved with either first (1LPT) or second (2LPT) order Lagrangian perturbation theory, in addition to the halos found with the peak patch method (these peak patch halos are also moved with either . Shown below are the same peak patch halo distributions, but with the density distribution run with an N-body simulation (courtesy of Jia Liu) instead.

Next Steps

  1. Halo model already integrated into exgal sim pipeline
  2. Integrate field model into exgal pipeline
  3. Run 8 Gpc/h 4096^3 resolution GRF in an octant of the sky going to z~4.5
  4. Project this run using halo+field model to make a z<4.5 kappa map (at Nside=8192)
  5. Add an uncorrelated kappa map corresponding to z>4.5 (at Nside=8192)
  6. Lens a primary CMB located on NERSC to create a lensed CMB map (with Alex and Julian)