Lenstool FAQ¶

Does the organization of the potentials in the .par file matter?¶

Yes. Internally in Lenstool, the potentials are all saved into a large array or pointers. Here is the assumed order in the lens[] array

             Indiv. optim. pot. | Fixed pot. |Potfile 0 | Potfile 1 | Accelerated pot. |
             ^                  ^            ^          ^           ^                  ^
             0              G.no_lens    G.nplens[0]  G.nplens[1]  G.nmsgrid         G.nlens

The G structure contains a set of indexes that mark each section in the lens[] array. During processing, each section might be processed differently according on its particular type. Some indexes are set by the user

Internal name	Name in the _.par file	Description
G.no_lens	grille / nlens_opt	End of the individually optimized potentials with limit section
G.nmsgrid	grille / nmsgrid	Beginning of the potentials optimized with the multiscale grid method (no limit section)
G.nlens	grille / n_lentille	Total number of potentials (reset automatically by Lenstool if too large)

The potfile indexes saved in the array nplens[] for the different potfiles are set automatically, according to the number of galaxies in each potfile. They mark the beginning of the potfile sections.

How can I speed up the calculations?¶

The optimization of the potfile can severly slows down the calculations, because Lenstool will compute the derivatives of the potential of all the potfile galaxies. If it happens that you already have an approximative idea of the potfile values, you can fix the "sigma" and "cutkpc" parameters. This will significantly speed up the calculations.

However, note that if you also optimize the redshift of the multiple images or the cosmological parameters, you will necessarily have to recompute the potfile.

In Ubuntu, I get a compilation error with Lenstool version 6.8¶

The error message contains many missing math functions (log, pow, sin, etc).

The solution is to type the gcc command line by hand, moving the "-lm" option to the end of the command line.

gcc -g -O2 -fopenmp -lcfitsio -o lenstool_tab e_nfwg.o lenstool_tab.o midpnt.o nrutil.o polint.o qromo.o read_bin.o -lm

How can I interact with DS9?¶

Lenstool package contains scripts to display regions in DS9, using the XPA binaries.

You can download the executables and install them anywhere. In your .bashrc, you then need to add them to the PATH

For bash shell (to know your shell, you can type echo $SHELL),

export PATH=$PATH:<your path to the xpa binaries>

For csh shell,

setenv PATH $PATH:<your path to the xpa binaries>

Once, you restart your shell, you should be able to open an image with DS9

ds9 my_image.fits

and display a Lenstool catalog of images

pelli image_wcs.cat