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The goal of the Pangloss project is to understand, model and account for the mass structure along the line of sight to various interesting objects in the Universe, whose apparent position, brightness and shape are all affected by the combined gravitational lensing effect of all that mass between them and us. In particular, we want to make accurate measurements of distances (cosmography) and high redshift luminosity functions, both of which count line of sight structure as one of their most serious systematic errors.
Pangloss is scientific code still under development. If you do want to see what we are doing, and play around with the code, you should contact Phil ([email protected]) to to let us know you are here, and then see the README for more advice.
The documentation of the code is in-place, but hopefully this page will help you navigate it.
"Reconstructing Every Galaxy - Is It Worth It, for Lens Cosmography?" Collett et al
This project grew in to our first paper, "Reconstructing the lensing mass in the universe from photometric catalogue data", Collett et al (2013).
"Application to the COSMOGRAIL Lens Sample" Marshall, Collett, Suyu, et al
We'll need some way of estimating the systematics introduced by the calibration step...
"Including Groups and Clusters - Can we avoid the calibration step?" Marshall and anyone else
Should be a straightforward extension to include a suitable group catalog. It is to be seen how good such catalogs are though. Can we include voids? Work with the simulations in 3D?
"Inferring Dark Mass Hierarchically, from Weak Lensing Data" Vanderplas? Hogg? Marshall, Brewer? etc
This is a big problem to take on... but would be a great one to solve! Starting with a simplified toy example will be essential: its the huge dimensionality inference that's the issue.
- Improve ray-tracing scheme beyond the current simple summation of lens planes. Keeton et al weights? Blandford propagation matrices? These will need testing, with suitable simulations...
- Keep track of shear as well as convergence: this is something the lens model can help constrain, after all. Shear calculation is already included - it's just not yet used in the calibration step (since everything goes through kappah_median).
- Include groups and clusters: optical cluster finders exist, and the latest ones even attempt a probabilistic assessment of cluster membership. The outputs from these codes will fit very nicely into our probabilistic framework.
- Move to 3D modeling of the smooth component: We tried to make this work, but couldn't quite. It deserves a bit mores tudy...
- Include voids, filaments and sub-galactic halos. This is probably three upgrades - but since we don't know which is most important yet, it seems sensible to keep these together...