ALIAS

Astrophysics Lasso Inverse Abel Solver

The data and code provided here are supplementary information for the paper

Non-parametric estimation of galaxy cluster's emissivity and point source detection in astrophysics with two lasso penalties

Authors: Jairo Diaz-Rodriguez, Dominique Eckert, Hatef Monajemi, Stephane Paltani and Sylvain Sardy

Abstract of the article:

Astrophysicists are interested in recovering the 3D gas emissivity of a galaxy cluster from a 2D image taken by a telescope. A blurring phenomenon and presence of point sources make this inverse problem even harder to solve. The current state-of-the-art technique is two step: First identify the location of potential point sources, then mask these locations and deproject the data. We instead model the data as a Poisson generalized linear model (involving blurring, Abel and wavelets operators) regularized by two lasso penalties to induce sparse wavelet representation and sparse point sources. The amount of sparsity is controlled by two quantile universal thresholds. As a result, our method outperforms the existing one.

C++ version: https://gitlab.com/philippeganz/alias (Credits to Phillippe Ganz)

PRELIMINARY REQUIREMENTS

- This code is implemented in MATLAB

Download and extract 'ALIAS.rar', available here.
Add folders 'ALIAS/FISTA', 'ALIAS/simfunc' and 'ALIAS/code' to MATLAB path.
Download and Install WAVELAB 850, available here.
Compile 'ALIAS/deprojection.C' in your own Operative System and locate it in folder 'ALIAS'. This file allows to do the inversion using the conventional method.

INSTRUCTIONS FOR USAGE

To perform all the analysis and generate all figures (and tables) in the paper with the existing simulated results, go to the root folder ‘ALIAS’ in MATLAB and run 'reproduceAnalysis’.
To perform all simulations in the paper, go to the root folder ‘ALIAS’ in MATLAB and run 'reproduceALL'.
By default it runs using parallel computations, you can change it by uncommenting options.parallel=0 and replacing 'parfor' by 'for', in all simulation files ('runSimTable1parallel.m', 'runSimFigure3parallel.m', and 'runRealDataParallel.m').
To get the estimates in a single image, use 'astrosolveWS.m'.
To simulate a telescope image and get the estimates, use 'astrosimPS.m'.
To get the estimates of a single image and obtain pointwise confidence interval by bootstrap use 'astrobootWS.m'.

REAL DATA

Real data concerning images from abell2142 (Chandra and XMM telescope) and from a3667, bullet, and perseus (XMM telescope) is available in file ‘realdata.mat’ as a 1x5 structure containing the telescope image (F), telescope sensitivity (E), and telescope background (O) for each of the 5 real data settings.

MIT license