Galaxies (glass.galaxies)#
The glass.galaxies module provides functionality for simulating galaxies
as typically observed in a cosmological galaxy survey.
Functions#
- glass.galaxies.redshifts_from_nz(count, z, nz, *, rng=None)#
Generate galaxy redshifts from a source distribution.
The function supports sampling from multiple populations of redshifts if count is an array or if there are additional axes in the z or nz arrays. In this case, the shape of count and the leading dimensions of z and nz are broadcast to a common shape, and redshifts are sampled independently for each extra dimension. The results are concatenated into a flat array.
- Parameters:
- countint or array_like
Number of redshifts to sample. If an array is given, its shape is broadcast against the leading axes of z and nz.
- z, nzarray_like
Source distribution. Leading axes are broadcast against the shape of count.
- rng
Generator, optional Random number generator. If not given, a default RNG is used.
- Returns:
- redshiftsarray_like
Redshifts sampled from the given source distribution. For inputs with extra dimensions, returns a flattened 1-D array of samples from all populations.
- glass.galaxies.galaxy_shear(lon, lat, eps, kappa, gamma1, gamma2, *, reduced_shear=True)#
Observed galaxy shears from weak lensing.
Takes lensing maps for convergence and shear and produces a lensed ellipticity (shear) for each intrinsic galaxy ellipticity.
- Parameters:
- lon, latarray_like
Arrays for galaxy longitudes and latitudes.
- epsarray_like
Array of galaxy ellipticity.
- kappa, gamma1, gamma2array_like
HEALPix maps for convergence and two components of shear.
- reduced_shearbool, optional
If
False, galaxy shears are not reduced by the convergence. Default isTrue.
- Returns:
- shearray_like
Array of complex-valued observed galaxy shears (lensed ellipticities).
- glass.galaxies.gaussian_phz(z, sigma_0, rng=None)#
Photometric redshifts assuming a Gaussian error.
A simple toy model of photometric redshift errors that assumes a Gaussian error with redshift-dependent standard deviation \(\sigma(z) = (1 + z) \sigma_0\) [1].
- Parameters:
- zarray_like
True redshifts.
- sigma_0float or array_like
Redshift error in the tomographic binning at zero redshift.
- rng
Generator, optional Random number generator. If not given, a default RNG is used.
- Returns:
- phzarray_like
Photometric redshifts assuming Gaussian errors, of the same shape as z.
See also
glass.observations.tomo_nz_gausserrCreate tomographic redshift distributions assuming the same model.
References
[1]Amara A., Réfrégier A., 2007, MNRAS, 381, 1018. doi:10.1111/j.1365-2966.2007.12271.x
Examples
See the Photometric redshifts example.