Spectral Correlated Noise

class galsim.CovarianceSpectrum(Sigma, SEDs)[source]

Class to hold a ChromaticSum noise covariance spectrum (which is a generalization of a power spectrum or equivalently a correlation function).

Analogous to how a galsim.CorrelatedNoise object stores the variance and covariance of a galsim.Image object, a galsim.CovarianceSpectrum stores the variance and covariance of the Fourier mode amplitudes in different components of a ChromaticSum.

Note that the covariance in question exists between different SED components of the ChromaticSum, and not between different Fourier modes, which are assumed to be uncorrelated. This structure arises naturally for a ChromaticRealGalaxy (see devel/modules/CGNotes.pdf for more details).

Parameters:

  • Sigma – A dictionary whose keys are tuples numerically indicating a pair of ChromaticSum components whose Fourier mode amplitude covariances are described by the corresponding GSObject values.

  • SEDs – SED instances of associated ChromaticSum components.

toNoise(bandpass, PSF, wcs, rng=None)[source]

Derive the CorrelatedNoise object for the associated ChromaticSum when convolved with PSF and drawn through bandpass onto pixels with specified wcs.

Parameters:

  • bandpass – Bandpass object representing filter image is drawn through.

  • PSF – output chromatic PSF to convolve by.

  • wcs – WCS of output pixel scale.

  • rng – Random number generator to forward to resulting CorrelatedNoise object.

Returns:

CorrelatedNoise object.