Weak Lensing with the Lyman-α Forest Prakruth Adari Anže Slosar 1
What? ● Remapping quasars and then using the displacement map we can get, to create a kappa map 2
Method We can create a displacement field and use that to get the kappa map Observed distance should be true distance + noise Can get likelihood for true positions 3
Least Squares For each pair, we have a solution so least squares fit for each quasar against its nearest neighbors Use first degree taylor expansion of great circle distance Set overdetermined system of linear equations for each i and find best fit A= = 4
Least Squares Fit 250, 000 points uniformly over a sphere with the 100 nearest neighbors 5
250 k points 6
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Samantha Prakruth 10
Limitations ● Computationally intensive due to iterations (149, 000 points is 3360 seconds per iteration on a single core) ● Doesn’t do well with edges/holes which can stem from not enough data ○ ○ Can find the unlensed positions but going from displacement field to kappa map is not good Correlation is resolution dependent 24 k points 11
Conclusions ● Able to get unlensed points in a non-ridiculous amount of time ○ ○ Able to get an accurate displacement map Non-ridiculous because of cluster access so it’s only kind of ridiculous ● Not able to get an accurate kappa map ○ Too many “holes” in the data lead to it being really spotchy 12