Documentation {#mainpage}

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](@ref install). If you would like to obtain the code, please see the [appropriate section](@ref copying).

The code can be made available to you through GitHub.com upon request. Requests should be sent to Ben Metcalf at [email protected].

Getting started

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.

Read in Parameters

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.

Cosmology

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.

LensHalo classes

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

Source Class

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

Lens class

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.

Grid & GridMap

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.

Image finding and Grid refinement

The mean functions used for image finding are

• ImageFinding::find_images_kist()
• ImageFinding::map_images_fixedgrid and
• ImageFinding::map_images(). And for finding critical curves / caustics
• ImageFinding::find_crit()

These take a Grid and a Lens object. The found images are then stored in an array of ImageInfo structures.

Observational effects

The Observation class is used to simulate pdf, noise, etc.

PixelMap class

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.

Output

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.