Analysis of luminosity distributions of strong lensing galaxies:
  subtraction of diffuse lensed signal
  Strong gravitational lensing gives access to the total mass distribution of
galaxies. It can unveil a great deal of information about the lenses dark
matter content when combined with the study of the lenses light profile.
However, gravitational lensing galaxies, by definition, appear surrounded by
point-like and diffuse lensed signal that is irrelevant to the lens flux.
Therefore, the observer is most often restricted to studying the innermost
portions of the galaxy, where classical fitting methods show some
instabilities. We aim at subtracting that lensed signal and at characterising
some lenses light profile by computing their shape parameters. Our objective is
to evaluate the total integrated flux in an aperture the size of the Einstein
ring in order to obtain a robust estimate of the quantity of ordinary matter in
each system. We are expanding the work we started in a previous paper that
consisted in subtracting point-like lensed images and in independently
measuring each shape parameter. We improve it by designing a subtraction of the
diffuse lensed signal, based only on one simple hypothesis of symmetry. This
extra step improves our study of the shape parameters and we refine it even
more by upgrading our half-light radius measurement. We also calculate the
impact of our specific image processing on the error bars. The diffuse lensed
signal subtraction makes it possible to study a larger portion of relevant
galactic flux, as the radius of the fitting region increases by on average
17\%. We retrieve new half-light radii values that are on average 11\% smaller
than in our previous work, although the uncertainties overlap in most cases.
This shows that not taking the diffuse lensed signal into account may lead to a
significant overestimate of the half-light radius. We are also able to measure
the flux within the Einstein radius and to compute secure error bars to all of
our results.
