construct_covariance_matrix

construct_covariance_matrix#

pygaia.utils.construct_covariance_matrix(cvec, parallax, radial_velocity, radial_velocity_error)#

Take the astrometric parameter standard uncertainties and the uncertainty correlations as quoted in the Gaia catalogue and construct the covariance matrix.

Parameters:

  • cvec (array_like) – Array of shape (15,) (1 source) or (N,15) (N sources) for the astrometric parameter standard uncertainties and their correlations, as listed in the Gaia catalogue [ra_error, dec_error, parallax_error, pmra_error, pmdec_error, ra_dec_corr, ra_parallax_corr, ra_pmra_corr, ra_pmdec_corr, dec_parallax_corr, dec_pmra_corr, dec_pmdec_corr, parallax_pmra_corr, parallax_pmdec_corr, pmra_pmdec_corr]. Units are (mas^2, mas^2/yr, mas^2/yr^2).

  • parallax (array_like) – Source parallax(es) array of shape (N,) (mas).

  • radial_velocity (array_like) – Source radial velocity (km/s, does not have to be from Gaia RVS!) as array of shape (N,). If the radial velocity is not known it can be set to zero.

  • radial_velocity_error (array_like) – Source radial velocity uncertainty (km/s), array of shape (N,). If the radial velocity is not know this can be set to the radial velocity dispersion for the population the source was drawn from.

Returns:

cmat – Covariance matrix as a Nx6x6 array.

Return type:

float array

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