autolens.FitPointDataset#

class FitPointDataset[source]#

Bases: object

Fits a point source dataset using a Tracer object, where the following components of the point source data may be fitted:

  • The positions of the point source in the image-plane, where the chi-squared could be defined as an image-plane or source-plane chi-squared.

  • The fluxes of the point source, which use the magnification of the point source to compute the fluxes in the image-plane.

  • The time delays of the point source in delays, which use the tracer to compute the model time delays at the image-plane positions of the point source in the dataset.

The fit may use one or combinations of the above components to compute the log likelihood, depending on what components are available in the point source dataset and the model point source profiles input. For example:

  • The ps.Point object has a centre but does not have a flux, so the fluxes are not fitted, meaning only positions are fitted.

  • The ps.PointFlux object has a centre and a flux, therefore both the positions and fluxes are fitted.

The fit performs the following steps:

  1. Fit the positions of the point source dataset using the input fit_positions_cls object, which could be an image-plane or source-plane chi-squared.

  2. Fit the fluxes of the point source dataset using the FitFluxes object, where the object type may be

extended in the future to support different types of point source profiles.

  1. Fits the time delays of the point source dataset using the FitTimeDelays object, which is an image-plane evaluation of the time delays at the image-plane positions of the point source in the dataset.

Point source fitting uses name pairing, whereby the name of the Point object is paired to the name of the point source dataset to ensure that point source datasets are fitted to the correct point source.

When performing a model-fit`via an `AnalysisPoint object the figure_of_merit of this object is called and returned in the log_likelihood_function.

Parameters:

  • dataset (PointDataset) – The point source dataset which is fitted.

  • tracer (Tracer) – The tracer of galaxies whose point source profile are used to fit the positions.

  • solver (PointSolver) – Solves the lens equation in order to determine the image-plane positions of a point source by ray-tracing triangles to and from the source-plane.

  • fit_positions_cls – The class used to fit the positions of the point source dataset, which could be an image-plane or source-plane chi-squared.

  • profile – Manually input the profile of the point source, which is used instead of the one extracted from the tracer via name pairing if that profile is not found.

Methods

Attributes

figure_of_merit

The figure_of_merit of the point source dataset, which is the value the AnalysisPoint object calls to perform a model-fit.

log_likelihood

Returns the overall log_likelihood of the point source dataset, which is the sum of the log likelihoods of each individual component of the point source dataset that is fitted (e.g. positions, fluxes, time delays).

model_obj

property model_obj#
property log_likelihood: float#

Returns the overall log_likelihood of the point source dataset, which is the sum of the log likelihoods of each individual component of the point source dataset that is fitted (e.g. positions, fluxes, time delays).

property figure_of_merit: float#

The figure_of_merit of the point source dataset, which is the value the AnalysisPoint object calls to perform a model-fit.