High resolution templates

so_pysm_models also provides access to templates with higher resolution and with updated data compared to the models included in PySM.

They can be accessed with the function get_so_models() which works similarly to the models function available in PySM, and you can mix them, for example:

from so_pysm_models import get_so_models
from pysm.nominal import models
from pysm import Sky
sky = Sky({
        "dust" : get_so_models("SO_d0", nside=128),
        "synchrotron" : models("s1", nside=128)
})

so_pysm_models retrieves the templates when needed from NERSC via web accessing: http://portal.nersc.gov/project/cmb/so_pysm_models_data/ Downloaded files are stored in the astropy cache, generally astropy/cache and are accessible using astropy.utils.data, e.g. astropy.utils.data.get_cached_urls() gives the list of downloaded files. If running at NERSC, the module automatically uses the files accessible locally from the /project filesystem.

Low-resolution templates are standard PySM ones at \(N_{side}\) 512, often with updated parameters based on Planck results. High-resolution templates are computed from the low-resolution ones, by extrapolating power spectra considering a simple power law model, and by generating small scales as Gaussian realization of these spectra. High-resolution templates therefore have Gaussian small scales (for \(\ell > ~ 1000\)) modulated with large scale signal for both temperature and polarization.

You can access the high resolution parameters at \(N_{side}\) 4096 appending s (for small scale) at the end of each model name, for example:

from so_pysm_models import get_so_models
from pysm import Sky
sky_highres = Sky({
        "dust" : get_so_models("SO_d0s", nside=4096),
        "synchrotron" : get_so_models("SO_s0s", nside=4096)
})

Whatever the \(N_{side}\) of the input model and the requested \(N_{side}\) in get_so_models(), PySM will automatically use healpy.ud_grade() to adjust the map resolution.

Details about individual models

Append “s” after a model name to access the \(N_{side}\) 4096 template, i.e. SO_f0s.

Dust

• SO_d0: Thermal dust is modeled as a single-component modified black body, with same templates as in PySM model d1. There is no spatial variation of temperature and emissivity in the sky: \(T=19.6\) K and \(\beta_d=1.53\) (values taken from Planck Collaboration IX 2018).

Synchrotron

• SO_s0: Templates from PySM model s1. Power law spectral energy distribution, with fixed spectral index \(\beta_s=-3.1\) (from Planck Collaboration IX 2018).

Free Free

• SO_f0: same model as PySM f1, no spatial variation of spectral index equal to -2.4.

AME

• SO_a0: sum of two spinning dust populations (as in PySM model a1) with spatially constant peak frequency. No polarization.