Putting Together the CMB-S4 Science Book Requirements Table
The Concept Definition Task Force has been tasked with writing down science requirements, with three suggested levels (sky's the limit, minimum worth doing, something in between). John C. has, in turn, asked the Science Book chapter leads to create a summary table of requirements from the book. Below are notes and discussions for each Science Book "science goal" chapter (intro, CMB lensing, and analysis/sims/forecasting not included). Chapter leads are particularly encouraged to contribute material and collate into a final recommendation. As per John C.'s email (and the recommendation of Jo Dunkley and others to the CDT), there is also an "astrophysics chapter" included in the discussions.
Theorist’s dream: σ(r)=1×10−6
Aspirational goal: σ(r)=5×10−4
Minimal goal: σ(r)=1×10−3
Both are for a fiducial value of r = 0 and must include foreground removal and systematics.
Theorist’s dream: σ(\sum mν)=8meV
Aspirational goal: σ(\sum mν)=15meV
Minimal goal: σ(\sum mν)=20meV
Both are for a normal mass hierarchy with \sum mν = 58 meV, rely on the lensing power spectrum, and include a prior from DESI BAO measurements and assume an external measurement of the optical depth with σ(τ) = 0.006.
Theorist's dream: σ(Neff)=0.005
Aspirational goal: σ(Neff)=0.027
Minimal goal: σ(Neff)=0.035
Some of these goals involve other data sets. It might be a natural to convert these require- ments to map-level requirements on noise-levels, foreground residuals, and systematics.
One area not covered by these requirements is cluster science. No clear targets were identified in the science book, but it is qualitatively clear that cluster science significantly benefits from higher resolution. For example at ”a 99% purity threshold, the 3, 2 and 1 arc- minute configurations would identify approximately 45,000, 70,000 and 140,000 clusters.” Furthermore, at 1 arcmin resolution one could begin to resolve clusters and study pressure profiles, learn about baryonic physics, etc. Clusters can also be used to constrain neutrino mass. To my knowledge sufficiently reliable forecasts for this do not exist.