Data Challenges

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At the SLAC meeting it was agreed to separate "experiment definitions" (bands, resolutions, sensitivity level) from "sky models" (LCDM+dust+sync+). Each of these will be designated by a number. The combination of a given experiment definition XX acting on a given sky model YY will be designated XX.YY.

Experiment models, sky models and the datasets obtained by applying for former to the latter will be stored at NERSC at
/project/projectdirs/cmbs4/{expt_xx, sky_yy, data_xx.yy}

Experiment Definitions

Experiment Definitions

Input Sky Components

Sky Components

Sky Models

Sky Models

To build the sky models the experiment bandpasses are already required. So far nominal tophat bands are being used - a complete list of the center and width is in this spreadsheet. The CMB-S4 specific band list is CMB-S4 frequency bands v1.99. What a tophat bandpass actually means is a little tricky and discussed in Bandpass Convention - What does flat mean. It seems that models 00/05/08/09 use nu^-2 in spectral radiance (SR) units, while models 01/02/03 use nu^0 in SR units. (What 06 uses is not known.)

Sky model 00

This is simply LCDM + Gaussian dust + Gaussian Sync. Since the dust and sync levels are set to the levels found in the BICEP/Keck field it wouldn't make any sense to use this model for a large sky fraction.

Sky Model 01

This is PySM run in a1d1f1s1 mode - i.e. with the default settings for AME, dust, free-free and synchrotron.

Sky Model 02

This is PySM run in a2d4f1s3 mode - GitHub for some description of what this means.

Sky Model 03

Versus 02 this switches the dust model to a Hensley/Draine model and is dubbed a2d7f1s3. (02 to 03 also marks the switch from pysm_1.0 to pysm_2.0 so the s2, f1, s3 components in principle change. Think the change is to do with the details of how the bandpass integration is being handled.)

Sky Model 04

This model switches the dust model to a Tuhin Ghosh provided model which implements dust decorrelation. See HI-based dust polarization model for r forecasts. The AME, sync and free-free components remain the same as 03

Sky Model 05

This is a toy model of dust which is highly decorrelated. See Toy highly decorrelated dust model. There is NO AME/sync/Free-free - only dust.

Sky Model 06

This is a model from Raphael Flauger and Brandon Hensley based on MHD sims of galactic magnetic field populated with dust and relativistic electrons according to this recipe: File:Sky models.pdf.

Sky Model 08

This is the model 06 with an alternate electron energy spectrum which gives a synchrotron spectrum closer to reality.

Sky Model 09

This is the Vansyngel Model.

Sim Data Sets

Many of the possible xx.yy combinations have been generated and are available on NERSC.

Most of 02.00 through 02.09 exist - these are the "Science Book config".

Most of 04.00 through 04.06 exist - these are the "CDT report config".


Shared space is available on NERSC, where everyone is welcome to sign-up for an account under the "Data Analysis for Post-Planck CMB Experiments" allocation (PI Borrill). The files are located in the shared CMB-S4 file space (/project/projectdirs/cmbs4). In order to manage this space, all files stored there should be owned by the cmbs4 project account but accessible to the cmbs4 group. To do this:

  • log in to the cmbs4 project account following the instructions [here]
  • sync the files to an appropriate subdirectory in the project space
  • ensure that the permissions are set appropriately (g+rX,o-rwx)

Remember to include a README and to post the details on this wiki page.

For any NERSC issues, including access to the filegroup and/or project account, please contact Julian Borrill.