# Forecasting

From CMB-S4 wiki

### Forecasting non-r parameters

The expectation is that these forecasts will be done mainly using Fisher forecasts for the Science Book, with prudent use of frequencies and ell-range to avoid being over-optimistic about the impact of Galactic and extragalactic foregrounds and noise from the ground.

#### Parameters

Names of people responsible for generating forecasts in brackets. Sign yourself up and we can divide up tasks when we speak if there are multiple people.

- LCDM 6-parameters (all)

- curvature (Stephen/Josquin) - also Danielle/Jo
- running (Stephen/Josquin)
- birefringence (Vera)
- correlated isocurvature amplitude (Cora/Kimmy)
- uncorrelated isocurvature amplitude (Cora/Kimmy)
- axion isocurvature (Renee/Doddy/Dan)
- cosmic string tension (Renee)
- primordial magnetic field (TBD)

- neutrino mass sum (Mat/Neelima/Nam) - also Alessandro
- Neff (with delensing of TT & EE (Joel/Alex/Dan) - also Mat/Neelima/Nam and Erminia
- Yp (with delensing of TT & EE (Joel/Alex/Dan) - also Erminia
- neutrino sound speed (Erminia)

- dark matter annihilation (Cora)
- dark matter interactions (Cora)
- utralight-axion density (Renee/Doddy/Dan G)
- w (Alessandro) - also Stephen/Josquin
- w0,wa (Alessandro) - also Stephen/Josquin
- early dark energy (Erminia)
- gamma (TBD)

Non-cosmological/other parameters:

- kSZ S/N from S4 x photo-z (Simone)
- shear bias calibration from S4 x LSST (Emmanuel)

Here is place-holder for some suggested fiducial parameters and step-sizes, can be different though.File:Params steps.pdf

#### Fisher codes

With info on what data they can handle and who is available to run them during next two months

- Errard/Feeney code -unlensed TT, EE, TE and BB, plus deflection dd. Can do iterative EBEB, CIB or LSS delensing, and foreground removal on a statistical level. Current white noise, but simple to extend (Stephen,Josquin)
- Allison et al code - lensed TT/TE/EE plus kk plus BAO, can take in non-white N_ell but no explicit FG handling (Danielle Leonard, Jo Dunkley)
- Extension of Allison et al code for axions (Renee Hlozek)
- Stony Brook code - TT/TE/EE/kk with iterative delensing plus BAO, can take in non-white N_ell but no explicit FG handling, being expanded to include LSST shear and cluster counts with halo lensing (Mat Madhavacheril, Neelima Sehgal, Nam Nguyen)
- de Bernardis code - includes kSZ likelihood (Francesco de Bernardis)
- Manzotti code- similar to Allison et al and already partially checked against that code; used for http://arxiv.org/abs/1512.02654 (Alessandro Manzotti)
- CITA code - includes delensing of spectra to all orders; forecasts of delensed covariances are in progress (Joel Meyers, Alex van Engelen, Dan Green)
- who has a tSZ likelihood? (David Alonso can do N(M,z) and tSZ fluxes. Who has code to push through to parameters?)
- other codes and people?

#### Settings

Nominal:

- S4 TT/TE/EE/kk over 40% of sky, 30<ell < lmax
- Planck TT/TE/EE from 30<l<2500 over additional 20% of sky. Use these 'Planck-pol' specs for noise:File:Planck pol.pdf
- Planck TT at l<30 over 80% of sky
- Tau prior 0.06+-0.01

- lmax(TT)=3000 unless explicit foreground cleaning is done in code for kSZ etc
- lmax(TE,EE)=5000 unless explicit foreground cleaning done in code
- kk reconstructed from 30<l<lmax using MV estimate

- quadratic estimator for lensing, ideally with iterative delensing
- Gaussian likelihood neglecting T/E/k covariance is ok, but non-Gaussian better (do any codes have full lensed T/E/B/k covariance?)
- non-linear power spectrum for kk, e.g. ok to use halofit in CAMB

Extensions:

- option to add DESI BAO. These are placeholder for forecast rs/DVs.File:Bao desi v2.pdf

- cluster masses calibrated with LSST lensing or CMB halo lensing (need to refine what that means)

#### Specs

*Nominal test case*

- Single channel (e.g. 150 GHz) at 1 uK/amin in T and 1.4uK/amin in P, 3 arcmin resolution.
- White noise, no FG inflation
- Useful if your code can spit out errors as function of noise level in 1-10 uK/arcmin range and resolution in range 1-10 arcmin.

*Next steps*

- Define multiple frequencies of the survey
- Decide if an N_ell that captures non-white-noise is necessary
- Define residual FG level if any