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The goal of the Pangloss project is to model and understand massive structures in the Universe, given photometric and gravitational lensing information about galaxies in wide field surveys. The original motivation was to be able to account for objects along the line of sight to various interesting targets, 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), high redshift luminosity functions, and cluster masses, all of which count line of sight structure as one of their most serious systematic errors. More generally, we are interested in making maps for their own sake: the connection between galaxies and their dark matter halos is of fundamental importance for understanding galaxy formation and evolution.
Pangloss is scientific code, still under development, for holistically modeling mass in the Universe on galaxy and cluster scales. This wiki tries to show what we are doing with it; if you want to play around with the code yourself, please contact Phil Marshall to let us know you are here, and then see the README for more advice.
The code is documented in-place, but hopefully this page will help you navigate it.
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"Reconstructing Every Galaxy - Is It Worth It, for Lens Cosmography?" Collett, Marshall 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).
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"Inferring the Mass Map of the Observable Universe from 10 Billion Galaxies" Marshall, Everett, Wechsler, Becker, Skillman, Collett et al, in progress. This is a big one: calibrating to weak lensing data, rather than simulations. One issue is the huge dimensionality integral involved when inferring the hyperparameters of the halo-based model; another is the need to include group and cluster mass distributions. This was the subject of a 2014 Stanford Data Science Initiative proposal, PI'd by Wechsler - dive in to read what we wrote. Spencer Everett worked on this project as a SLAC summer intern in 2015, and then for his senior undergraduate thesis in Winter 2016.
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"Calculating Weak Magnification PDFs for Survey Fields" Mason, Collett et al. Calculating magnification pdfs from Millennium Simulation data - for sources at z
8! Then matching to survey data fields (in this case BoRG) via overdensity. Used in _"Correcting the z8 Galaxy Luminosity Function for Gravitational Lensing Magnification Bias"_, Mason et al (2015).