Paul Shah and Tamara Davis tell us about how they have used this wonderful supernova catalogue from the Dark Energy Survey to detect the weak lensing magnification signal for the first time. There has been evidence of this signal in earlier catalogues, but at no bigger than 1.4σ. They’ve got it at 6σ!
They do this by correlating the scatter in the magnitude of the supernovae with the over-under density in galaxy catalogues along the same lines of sight of the supernovae. Where there is more matter, the light from the supernova should be magnified, and where there is less matter it should be de-magnified. And they do indeed see that along overdense lines of sight the supernovae are, on average, ever so slightly brighter, and on underdense lines of sight the are ever so slightly dimmer.
I can’t wait to see how this observable is used in the future to constrain all sorts of bits of cosmology. Nice work everyone!
Paper: arXiv: 2406.05047
Paul: paulshah.github.io
Cosmology Talks 