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GLAMERDOC++
Gravitational Lensing Code Library
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GLAMER is a flexible computer code for doing simulations of gravitational lensing and modelling of gravitational lenses.
This page describes the steps to doing a simple simulation and where in the documentation to find further information. The installation and usage of GLAMER is described on the installation page. If you would like to obtain the code, please see the appropriate section.
The code can be made available to you through GitHub.com upon request. Requests should be sent to Ben Metcalf at robertbenton.metcalf@unibo.it.
GLAMER is in the form of a C++ library that can be linked into your code.
For instructions on installing and linking the library see here
An overview of how the code is structured follows.
Originally all objects where constructed from a parameter file through the InputParams class. Many of these constructors still exist, but this method has been deprecated. It is recommended that the classes be constructed from their other constructors now.
First you must create an instance of the COSMOLOGY class. This is taken as an argument to many of the constructors and contains functions for calculating cosmological quantities. Several standard cosmological parameters sets are available or a new set can be chosen.
To represent the mass that causes the lensing one or more LensHalo objects must be constructed. A full list of LensHalos can be found here. Some examples are:
LensHaloNFW - a NFW halo
LensHaloMassMap - a mass sheet represented with a pixelized map
LensHaloParticles - a mass distribution represented by particles or point masses possibly from a simulation
LensHaloRealNSIE - a non-singular isothermal elliptical lens
LensHaloPowerLaw - a lens with a power-law mass profile
LensHaloUniform - to create a uniform shear and/or convergence
Sources represent anything that produces a visible image in front of, within or behind the lens.
Some of them are:
SourceUniform : Makes the source a uniform surface brightness circle
SourceGaussian : Source with a Gaussian profile
SourceShapelets : a source made from a shapelet decomposition
SourceSersic : a source with a Sersic profile
SourcePixelled : a source made from a pixelized image of an object
The lens class contains the LensHalos and keeps the information about the light-cone.
LensHalos are inserted into the Lens object with there redshift and angular position. Once it is created the Lens owns copies of the LensHalos. (Large LensHalos can be moved into the Lens using a move copy to avoid too much memory use.)
Lens::ResetSourcePlane() is used to change the redshift of the source plane. It can be at lower redshift than some or all of the LensHalos.
Main halos are ones that are inserted into the lens. Field halos are those that are generated within the Lens as a population throughout the light cone. These are stored differently within the Lens.
The Grid structure contains the image points and their source points along with other information. Without further grid refinement the Grid can be used to make a map of deflection, convergence, shear or time-delay. Grid contains functions for outputting these. If no further grid refinement is desired for image or caustic finding, the GridMap structure can be used which requires significantly less memory overhead and is faster.
When a Grid is constructed the initial grid of rays are shot. If no more refinement is needed the Lens is no longer needed. If source plane is changed a new Grid needs to be constructed for that source plane.
To change the source plane surface brightness use Grid::RefreshSurfaceBrightnesses (). This takes a Source object.
The mean functions used for image finding are
ImageFinding::find_images_kist()ImageFinding::map_images_fixedgrid andImageFinding::map_images(). And for finding critical curves / causticsImageFinding::find_crit()These take a Grid and a Lens object. The found images are then stored in an array of ImageInfo structures.
The Observation class is used to simulate pdf, noise, etc.
A PixelMap is an all purpose class to represent regular grids such as images and mass maps. It also allows for input / output with fits files.
The Grid has some direct output functions for making maps that do not depend on sources (kappa, gamma, etc.). The ImageInfo structure has information about the images found and contains a linked list of all the points within the image. Each point contains information about the kappa, gamma, source position, time-delay and in some cases the the surface brightness at that image position.
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