Mass models

setlens Ngal Nmod
  ID p[1] x y e te g tg p[8] p[9] p[10]     # galaxy #1
  ID p[1] x y e te g tg p[8] p[9] p[10]     # galaxy #2
  ...
  0 0 0 0 0 0 0 0 0 0
  0 0 0 0 0 0 0 0 0 0
  ...

(The command used to be called startup instead of setlens. I think setlens is more intuitive, but you can still use startup as well.)

Here Ngal is the number of galaxies per model, while Nmod is the number of different models you are giving.

Each galaxy is specified by a text label and 10 parameters. The parameters are as follows:

• p[1] : some lensing strength
• (x,y) : position
• (e,te) : ellipticity and its position angle
• (g,tg) : shear and its position angle
• p[8], p[9], p[10] : utility parameters

After giving the model parameters, you give a set of flags (the rows of 0's above). These indicate which parameters are allowed to vary in modeling.

Here is a table of the mass models available in gravlens/lensmodel.