High ell topics

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Jim writing

Science Topic 1: Growth of structure through sigma8(z)

Continue measurement of sigma8(z) with same precision as LSST to the redshift range 1<z<3, limited by sample variance in bins of dz=0.2 (dt/t~0.1) using clusters of M>1e14 Msol.


- Tie requirement to existing requirement from LSST in low-z universe

- If the mass function has an effective slope of beta at this mass scale, the sample variance requirement translates into a requirement on the individual mass measurement uncertainty from lensing: 1/sqrt(N) ~ beta*sigma_lensing/sqrt(N), where N is the number of clusters in a bin => sigma_lensing ~1/beta ~ 0.3-0.2. This is nice because places a requirement on lensing reconstruction per halo at our scale of 1e14 Msol that is close to the best that can be done with lensing (LSS, orientation and correlated structure noise). We therefore push on lensing requirements, and the CDT is looking for such lensing requirements. Moreover, from the estimates that we and have made (Jean-Baptiste and I, Nick, Matt, etc), it looks like this pushes into the range of 1-2 arcmin beam and 1 microK-arcmin sensitivity. This puts our game in the right ballpark.

- The requirement in dz would match a measurement of sigma8 in bins of approximately constant 1/10 fraction of the Hubble time over the range 1<z<3. This seems reasonable as we could expect that the evolution of something cosmological should scale with the Hubble time.

- Finally, the actual numerical precision from LSST on sigma8(z) will then set the survey area for CMB-S4.

Additional Science Requirement: Production of a cluster catalog with XX objects at z>1…. TO DEVELOP. This catalog will likely be a mission product.

Science Topic 2: Feedback/environments

A) Measurement of energy injection into and non thermal support of CGM, and of CGM mass as a function of galaxy properties (e.g., SFR, AGN activity), host halo mass and redshift to the 5-10% level over 1e12 < M/Msol < 1e15 and 0<z<3 in bins of lim = 0.2 and dz=0.2 Motivation:

- Expected level of non thermal support is 5-10% according to current models.

- Star formation converts 5-10% of baryons into stars, and this is the level of change observed in clusters in the gas and stellar mass content.

- Mass and redshift range cover halos responsible for majority of star formation from before the peak of cosmic star formation at z~2 down to the present.

- Redshift binning motivated as above

- Mass binning - seems reasonable…

NOTE 1: this is written as a science requirement. I think in this context, David’s suggestion of 5-10% measurement of a characteristic radius is the next step, i.e., a measurement requirement. Charles can comment.

B) Relative distribution of galaxies, diffuse gas and total mass over comoving scales 1 Mpc < L < 200 Mpc and redshift range 0<z<3-5 to XX% in bins of dk = YY and dz=0.2 Motivation:

- Complete census of what the baryons and dark matter distributions are from cluster scales to scales larger than than the BAO peak from before the peak of star formation until the present - Redshift binning motivated as above

- NEED reasonable numbers for XX and YY in particular.

NOTE: We should use this opportunity to establish science requirements on the lensing reconstruction in the field. The CDT is looking for such requirements on lensing reconstruction as the lensing map will likely be a mission product, like the cluster catalog.

Science Topic 3: Reionization with kSZ