Inputting Fits Mass Map

Lens planes in GLAMER can be input as fits maps. There are two formats for these input maps. One is called a MOKA map and one we call a pixel map. The MOKA format is particular to another code for producing cluster lenses so we will just describe the pixel maps here which are of more general interest.

###Parameters in the Parameter file

To input mass maps as lens planes you must set the fallowing two parameters in the parameter file:

pixelmaps_on - This turns on the lensing by the planes if set to 1. They can be turned off by setting it to 0 or leaving the parameter out.

pixelmaps_input_file - Path to density map(s) to be read in as main lens. This can be a single map (*.fits) or a file with a list of fits files in which case it should not have the .fits suffix.

In addition there is the optional parameter you can set the zero pad

pixelmaps_padding_factor - An integer that sets the factor by which the map is padded when doing FFTs. The default is 4.

###Header keyword requirements:

Besides the dimensions of the map in number of pixels, the mass map must have the following key words in its header to be read in.

PHYSICALSIZE - This is the size of the map in n the x-direction in degrees 
PIXELUNITS   - This is the mass units of the pixels in solar masses.  Factors of h 
              must be included.

The code then has several ways to set the distance to the lens plane. It first searches for the key words

DLLOW, DLUP - These are the comoving angular size distances to the nearest and furthest 
               walls of the shell that has been extracted from a simulation.

If those keywords are not found the code uses the redshift of the map set by

REDSHIFT or ZLENS  - This is the redshift of the mass sheet that is being entered.
              The redshift of lens plans can be changed through the Lens class 
              but in general it is better to have these set by the header information 
              and leave it unchanged.

If the header is missing this information GLAMER will print a warning and then might pick default values appropriate for a particular set of simulations that have been used in the past.

###Other issues

The deflection, shear and time-delay potential are calculated by use of the FFT. The maps are automatically zero padded to reduce boundary effects.