Data Challenges

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At the Chicago meeting it was agreed that it would be useful to provide common inputs for all science forecasting, to include extra-galactic foreground, galactic foreground and noise maps at a range of frequencies. It was further agreed that, in order to support the widest range of uses, these would be provided as all-sky HEALPix maps at Nside-8192.

Possible sky-model inputs are:

  • Extra-galactice: Alvarez/Battaglia/Bond, PSM
  • Galactic: pySM, PSM

Please add to these lists as appropriate.

Inputs will be hosted at 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 will then be 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.

Data Challenge 1

Intended as a simple test to develop our practice, compare spectral- and map-based forecasting, contrast different map-based codes and methods, and coordinate r and non-r science forecasting.

Maps pager for data challenge 1

Combined noise + lensed-ΛCDM + dust + sync maps are posted on NERSC in directory:

 /project/projectdirs/cmbs4/data_challenges/phase1/sky/comb/map/

Instrument specification

Frequency (GHz) 30 40 85 95 145 155 220 270
Bandwidth (GHz) 9.0 12.0 20.4 22.8 31.9 34.1 48.4 59.4
Beam FWHM (arcmin) 76.6 57.5 27.0 24.2 15.9 14.8 10.7 8.5

Beam window functions for each frequency can be found on NERSC in:

 /project/projectdirs/cmbs4/data_challenges/phase1/sky/wfunc/

In addition to beam smoothing at high ell, these window functions drop sharply to zero below ell=30 (maps for the data challenge contain no information below ell=30).

Scalar, tensor & non-Gaussian CMB: Borrill

Lensed scalar CMB, consistent with Planck 2015 and low τ parameters

  • Lensed CMB maps are posted on NERSC in directory:
 /project/projectdirs/cmbs4/data_challenges/phase1/sky/llcdm/map/

Unlensed CMB?

Corresponding Kappa Maps?

Extragalactic foregrounds: Alvarez / Battaglia / Bond / Stein

Not included in Data Challenge 1

Galactic foregrounds

Gaussian dust

  • Amplitude (in BB spectrum) is 4.25 μK2 at &nu = 353 GHz, ℓ = 80. This is the value that was used for Science Book forecasts and is listed in Victor's 2016-05-31 posting (Section 2). It also corresponds to the best fit dust amplitude from the BK14 result.
  • Dust amplitude in EE is 2x larger than BB. Dust amplitude in TT is 10x larger than EE (20x larger than BB). There is no TE, TB, or EB correlation.
  • Dust scaling in frequency follows a greybody spectrum with βdust = 1.6 and Tdust = 19.6 K.
  • Dust D scaling follows a power law in ell with exponent αdust = -0.4.
  • Dust maps are posted on NERSC in directory:
 /project/projectdirs/cmbs4/data_challenges/phase1/sky/gdust/map/

Gaussian synchrotron

  • Amplitude (in BB spectrum) is 3.8 μK2 at &nu = 23 GHz, ℓ = 80. This is the value that was used for Science Book forecasts and is listed in Victor's 2016-05-31 posting (Section 2). It also corresponds to the 95% upper limit from the BK14 result.
  • Sync amplitude in EE is 2x larger than BB. Dust amplitude in TT is 10x larger than EE (20x larger than BB). There is no TE, TB, or EB correlation.
  • Sync scaling in frequency follows a power-law spectrum with βsync = -3.1.
  • Sync D scaling follows a power law in ell with exponent αsync = -0.6.
  • Sync maps are posted on NERSC in directory:
 /project/projectdirs/cmbs4/data_challenges/phase1/sky/gsync/map/

Noise: homogeneous isotropic matched to N_ell: Victor / Clem / Colin / John K

White + 1/ℓ noise

  • N functional form and parameters listed in Victor's 2016-12-20 posting (Table 2).
  • Noise aℓm are calculated out to ℓ = 4096, but maps are rendered at nside = 512 with ℓmax = 2048. No beam smoothing is applied.
  • Full sky noise maps are generated from N, then scaled by the square root of variance map to produce noise that is lowest in the center of the observed field and blows up towards the edge.
  • Noise maps are posted on NERSC in director:
 /project/projectdirs/cmbs4/data_challenges/phase1/sky/noise/map/
  • Maps with filename like r0000_f030_n512.fits are full sky noise maps. Filenames like r0000_f030_n512_b00p0_mfsky03.fits have been multiplied by the square root of variance map.

Masks: Clem

Noise inverse variance map is defined as a flat circular region with radius = 12°, surrounded by a tapered region that falls to zero with cos profile over an additional 15 degrees. This map is defined to range from 0 (in unobserved pixels) to 1 (in the flat 12° circular region); noise simulations are generated over the full sky from a C_l spectrum, then multiplied by 1 / sqrt(inverse variance) so that the noise amplitude blows up near the edge of the field.

  • (Sum of inverse variance map) / (# of pixels in full sky) = 0.0293, so total noise power should be equivalent to fsky = 3%.
  • Fraction of pixels that are observed is 5.4%.

File located on NERSC at:

 /project/projectdirs/cmbs4/data_challenges/phase1/sky/amask/map/fsky03_fall_n512.fits

Analysis

Schedule

  • Dec 7: Beta version of Phase 1 maps
  • Dec 14: Telecon
  • Dec 17: Noise power (N_ell) prescriptions to Clem from Victor and Colin
  • Dec 21: A few realizations of Phase 1 maps delivered by Clem
  • Dec 21: Telecon (note phase shift)
  • Jan 4: Telecon
  • Jan 12: 100 realizations of Phase 1 maps posted to NERSC
  • Jan 18: Telecon
  • Feb 1: Telecon
  • Feb 15: Telecon
  • Feb 27, 28, Mar 1: S4 general meeting at SLAC
  • Mar 2, 3: S4 CDT meeting at SLAC