PrecomputedAlms

class so_pysm_models.PrecomputedAlms(filename, input_units='uK_CMB', input_reference_frequency_GHz=None, target_nside=None, target_shape=None, target_wcs=None, precompute_output_map=True, has_polarization=True, pixel_indices=None)

Bases: object

Generic component based on Precomputed Alms

Load a set of Alms from a FITS file and generate maps at the requested resolution and frequency assuming the CMB black body spectrum. A single set of Alms is used for all frequencies requested by PySM, consider that PySM expects the output of components to be in uK_RJ.

See more details at https://so-pysm-models.readthedocs.io/en/latest/so_pysm_models/models.html

Parameters:

filename : string

Path to the input Alms in FITS format

input_units : string

Input unit strings as defined by pysm.convert_units, e.g. K_CMB, uK_RJ, MJysr

input_reference_frequency_GHz : float

If input units are K_RJ or Jysr, the reference frequency

target_nside : int

HEALPix NSIDE of the output maps

precompute_output_map : bool

If True (default), Alms are transformed into a map in the constructor, if False, the object only stores the Alms and generate the map at each call of the signal method, this is useful to generate maps convolved with different beams

has_polarization : bool

whether or not to simulate also polarization maps Default: True

pixel_indices : ndarray of ints

Output a partial maps given HEALPix pixel indices in RING ordering

Methods Summary

compute_output_map(alm)
signal([nu, fwhm_arcmin, output_units])	Return map in uK_RJ at given frequency or array of frequencies

Methods Documentation

compute_output_map(alm)

signal(nu=[148.0], fwhm_arcmin=None, output_units='uK_RJ', **kwargs)

Return map in uK_RJ at given frequency or array of frequencies

If nothing is specified for nu, we default to providing an unmodulated map at 148 GHz. The value 148 Ghz does not matter if the output is in uK_RJ.

Parameters:

nu : list or ndarray

Frequency or frequencies in GHz at which compute the signal

fwhm_arcmin : float (optional)

Smooth the input alms before computing the signal, this can only be used if the class was initialized with precompute_output_map to False.

output_units : str

Output units, as defined in pysm.convert_units, by default this is “uK_RJ” as expected by PySM.

Returns:

output_maps : ndarray

Output maps array with the shape (num_freqs, 1 or 3 (I or IQU), npix)