Sample of realistic strong lens sightlines

[drphilmarshall]

Listening to @tcollett 's talk just now, here at the STRIDES/H0LiCOW meeting, it occurred to me that at some point soon we are going to want to be able to generate mock strong lens sightlines, in order to investigate their local environment (as well as their line-of-sight) mass distributions. I think we can only do this for non-central galaxies (because we cannot easily remove the effect of that galaxy on the ray-traced convergence and shear). An algorithm could be:

1. Select a Type 1 MS galaxy with i-band magnitude, stellar mass, and redshift "close to" a z~zs OM10 lens galaxy (somehow)
2. Find it's radius $r$ and azimuth $\phi$ relative to its central galaxy
3. Sample 50 random azimuths at this radius, and choose the one with the lowest ray-traced convergence (to make sure we don't land on another group galaxy, but instead in empty space)

While the ray-traced shear and convergence are not quite the quantities we need for strong lens modeling, they can (I think) at least be treated as reasonable indicators - in the sense that if we can predict shear and convergence accurately, its not implausible that we could also accurately predict the actual strong lens environment corrections. (This is the same working assumption as in our current weak lensing prediction program.)

Once we have a sample of such "mock lenses" we can make mock weak lensing catalogs for 40'x40' fields around them, and do our WL tests in the context of strong lens correction. Thoughts? @sweverett