Observations (glass.observations)

The glass.observations module provides functionality for simulating observational effects of surveys.

Redshift distribution

glass.observations.gaussian_nz(z, mean, sigma, *, norm=None)

Gaussian redshift distribution.

The redshift follows a Gaussian distribution with the given mean and standard deviation.

If mean or sigma are array_like, their axes will be the leading axes of the redshift distribution.

Parameters:

zarray_like

Redshift values of the distribution.

modefloat or array_like

Mean(s) of the redshift distribution.

sigmafloat or array_like

Standard deviation(s) of the redshift distribution.

normfloat or array_like, optional

If given, the normalisation of the distribution.

Returns:

nzarray_like

Redshift distribution at the given z values.

glass.observations.smail_nz(z, z_mode, alpha, beta, *, norm=None)

Redshift distribution following Smail et al. (1994).

The redshift follows the Smail et al. [1] redshift distribution.

Parameters:

zarray_like

Redshift values of the distribution.

z_modefloat or array_like

Mode of the redshift distribution, must be positive.

alphafloat or array_like

Power law exponent (z/z0)^alpha, must be positive.

betafloat or array_like

Log-power law exponent exp[-(z/z0)^beta], must be positive.

normfloat or array_like, optional

If given, the normalisation of the distribution.

Returns:

pzarray_like

Redshift distribution at the given z values.

Notes

The probability distribution function \(p(z)\) for redshift \(z\) is given by Amara & Refregier [2] as

\[p(z) \sim \left(\frac{z}{z_0}\right)^\alpha \exp\left[-\left(\frac{z}{z_0}\right)^\beta\right] \;,\]

where \(z_0\) is matched to the given mode of the distribution.

References

[1]

Smail I., Ellis R. S., Fitchett M. J., 1994, MNRAS, 270, 245

[2]

Amara A., Refregier A., 2007, MNRAS, 381, 1018

glass.observations.fixed_zbins(zmin, zmax, *, nbins=None, dz=None)

tomographic redshift bins of fixed size

This function creates contiguous tomographic redshift bins of fixed size. It takes either the number or size of the bins.

Parameters:

zmin, zmaxfloat

Extent of the redshift binning.

nbinsint, optional

Number of redshift bins. Only one of nbins and dz can be given.

dzfloat, optional

Size of redshift bin. Only one of nbins and dz can be given.

Returns:

zbinslist of tuple of float

List of redshift bin edges.

glass.observations.equal_dens_zbins(z, nz, nbins)

equal density tomographic redshift bins

This function subdivides a source redshift distribution into nbins tomographic redshift bins with equal density.

Parameters:

z, nzarray_like

The source redshift distribution. Must be one-dimensional.

nbinsint

Number of redshift bins.

Returns:

zbinslist of tuple of float

List of redshift bin edges.

glass.observations.tomo_nz_gausserr(z, nz, sigma_0, zbins)

tomographic redshift bins with a Gaussian redshift error

This function takes a _true_ overall source redshift distribution z, nz and returns tomographic source redshift distributions for the tomographic redshift bins given by zbins. It is assumed that sources are assigned a tomographic redshift bin with a Gaussian error [1]. The standard deviation of the Gaussian depends on redshift and is given by sigma(z) = sigma_0*(1 + z).

Parameters:

z, nzarray_like

The true source redshift distribution. Must be one-dimensional.

sigma_0float

Redshift error in the tomographic binning at zero redshift.

zbinslist of tuple of float

List of redshift bin edges.

Returns:

binned_nzarray_like

Tomographic redshift bins convolved with a gaussian error. Array has a shape (nbins, len(z))

See also

equal_dens_zbins

produce equal density redshift bins

fixed_zbins

produce redshift bins of fixed size

References

[1]

Amara A., Réfrégier A., 2007, MNRAS, 381, 1018. doi:10.1111/j.1365-2966.2007.12271.x

Visibility

glass.observations.vmap_galactic_ecliptic(nside, galactic=(30, 90), ecliptic=(20, 80))

visibility map masking galactic and ecliptic plane

This function returns a visibility map that blocks out stripes for the galactic and ecliptic planes. The location of the stripes is set with optional parameters.

Parameters:

nsideint

The NSIDE parameter of the resulting HEALPix map.

galactic, ecliptic(2,) tuple of float

The location of the galactic and ecliptic plane in their respective coordinate systems.

Returns:

visarray_like

A HEALPix visibility map.

Raises:

TypeError

If the galactic or ecliptic arguments are not pairs of numbers.