fraction_to_r

petrofit.petrosian.fraction_to_r(fraction, r_list, flux_list, r_petrosian, flux_err=None, r_petrosian_err=None, epsilon=2.0, epsilon_fraction=0.99, interp_kind='cubic', interp_num=5000)

Given photometric values and r_total_flux, calculate radius which encloses a specified fraction of the total flux.

Parameters:

fractionfloat

Fraction of flux total flux enclosed in target radius.

r_listnumpy.array

Array of radii in pixels.

flux_listnumpy.array

Array of photometric flux values.

r_petrosianfloat

Petrosian radius

flux_errint or numpy.array, optional

Array of errors in the flux values. If None, erros are not computed even if r_petro_err is provided.

r_petrosian_errfloat, optional

1-sigma error in r_petro. If set to None and flux_err is provided, r_petro_err is assumed to be 0 when computing errors.

epsilonfloat, default=2.

Epsilon value (used to determine r_epsilon). N.B: r_epsilon = r_petrosian * epsilon`

epsilon_fraction: float, default=0.99

Fraction of total flux that is recovered by r_petrosian * epsilon.

interp_kindstr or int, optional

Specifies the kind of interpolation used on the curve of growth (i.e r_list vs flux_list)

interp_numint

Number of interpolation function sampling radii.

Returns:

r_fraction_fluxfloat or numpy.nan

Radius which encloses a specified fraction of the total flux (determined by the Petrosian profile).

r_fraction_flux_errorfloat or numpy.nan

Error in r_fraction_flux.