# Sky Components

From CMB-S4 wiki

These are effectively a library of component skies which can be added up to produce models of what the total CMB+foreground sky might look like under different assumptions.

### Scalar CMB: Borrill

- consistent with Planck 2015 and low τ parameters
- alm's for 1000 realizations of LCDM are on NERSC in directory:
**/project/projectdirs/cmb/data/generic/cmb/ffp10/mc/scalar**with the input spectra in**/project/projectdirs/cmb/data/generic/cmb/ffp10/cls** - Both lensed and unlensed alm's are provided for each realization with names like
**ffp10_lensed_scl_cmb_000_alm_mc_0000.fits**and**ffp10_unlensed_scl_cmb_000_tebplm_mc_0000.fits** - The lensing map appears to be in the fourth binary table of
**ffp10_unlensed_scl_cmb_000_tebplm_mc_0000.fits**

### Tensor CMB: Borrill

- alm's for 1000 realizations of IGW tensors are on NERSC in directory:
**/project/projectdirs/cmb/data/generic/cmb/ffp10/mc/tensor**with the input spectra in**/project/projectdirs/cmb/data/generic/cmb/ffp10/cls** - these have a tensor/scalar ratio of 0.01, so for other values need to rescale them by 10*sqrt(r)

### Gaussian dust

- Amplitude (in BB spectrum) is 4.25 μK
^{2}at ν = 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 β
_{dust}= 1.6 and T_{dust}= 19.6 K. This choice of parameters comes from PIPXXX. - Dust D
_{ℓ}scaling follows a power law in ell with exponent α_{dust}= -0.4. This parameter also comes from PIPXXX. - These cls, alms and maps are posted on NERSC under directory:
**/project/projectdirs/cmbs4/input_sky_comps/gdust**

### Gaussian synchrotron

- Amplitude (in BB spectrum) is 3.8 μK
^{2}at ν = 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. Sync 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 β
_{sync}= -3.1. - Sync D
_{ℓ}scaling follows a power law in ell with exponent α_{sync}= -0.6. - These cls, alms and maps are posted on NERSC under directory:
**/project/projectdirs/cmbs4/input_sky_comps/gsync**

### PySM

- Maps of the PySM model have been provided at
**/project/projectdirs/cmb/data/generic/galactic/pysm_X.0** - There is a single realization at each frequency integrated over top hat bandwidths.
- Three variants are currently provided dubbed
**a1d1f1s1**,**a2d4f1s3**and**a2d7f1s3**- see the paper linked above and GitHub for some description.