calculation of critical lines

[Guido Davoli]

Dear all,

I'm a student and I'm new to Lenstool and lensing modeling. I'm trying to understand how Lenstools works and I'm performing some tests.
I built a distribution of clumps on the lens plane at zlens=0.544, I placed the source plane at zsource=1.0 and I asked Lenstool to calculate convergence (k) and shear (s) maps on the lens plane. Then I calculated the tangential eigenvalue map as 1-k-s. Points on this map with value=0 should represent the tangential critical line.
If I compare them with the critical points calculated by lenstool (on ds9, with the command pcl critic ) I find no match.

In the runmode section of the .par file convergence and shear are calculated with:

mass   1 1024 0.544 convergence.1.fits
shear  1 1024 1.0 shear.1.fits

the source section is:

source
  z_source   1.0
  end

the cline section is:

cline
  nplan   1 1.0
  dmax   180.0
  algorithm   MARCHINGSQUARES
  pas   1.0
  limitHigh   2.0
  limitLow   0.2
  end

Where I'm wrong?
Thanks!

Best regards,

Guido Davoli

[Johan Richard]

Dear Guido,

The critical line will correspond to the points where det(A)=(1-kappa)^2-gamma^2=0, where

kappa is the convergence and gamma the shear. I am not sure what would your tangential

eigenvalue map correspond to ?

Johan

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[Johan Richard]

Sorry I just understood what you meant and you are right the critical line should cover the zero values.

Can you show a picture of the difference between the map and the critical line ?

Did you check anything from the information on screen that would look suspicious ?

Johan

[keren sharon]

In some cases the redshift for kappa should be the source redshift rather than the cluster redshift, can you check that that's the case? 

It would also be useful to compare the critical curves to the magnification map that lenstool produces, this way you'll know which one is incorrect (your calculation vs. the critical curves). I find that the critical curves always agree well with the magnification output of lenstool.

Cheers,

-keren

 

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Keren Sharon
Assistant Professor
University of Michigan, Department of Astronomy

[Guido Davoli]

Dear all,

I just found a mistake in my code for the calculations of critical lines. Lenstool works fine!
Thank you all for your help.

Cheers,

Guido

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Da: lens...@googlegroups.com <lens...@googlegroups.com> per conto di keren sharon <sharon...@gmail.com>
Inviato: mercoledì 7 dicembre 2016 20.57.21
A: lens...@googlegroups.com
Oggetto: Re: [lenstool 215] calculation of critical lines

 

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