## Cosmology Talks: Marika Asgari on Kids 1000

It’s time I shared another one of those interesting cosmology talks on the Youtube channel curated by Shaun Hotchkiss. This channel features technical talks rather than popular expositions so it won’t be everyone’s cup of tea but for those seriously interested in cosmology at a research level they should prove interesting. Since I haven’t posted any of these for a while I’ve got a few to catch up on – this one is from September 2020.

In this talk Marika Asgari tells us about the recent Kilo-Degree Survey (KiDS) cosmological results. These are the first results from KiDS after they have reached a sky coverage of 1000 square degrees. Marika first explains how they know that the results are “statistics dominated” and not “systematics dominated”, meaning that the dominant uncertainty comes from statistical errors, not systematic ones. She then presents the cosmological results, which primarily constrain the clumpiness of matter in the universe, and which therefore constrain Ω_{m} and σ_{8}. In the combined parameter “S_{8}“, which is constrained almost independently from Ω_{m} by their data they see a more than 3σ tension with the equivalent parameter one would infer from Planck.

P. S. The papers that accompany this talk can be found here and here.

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January 18, 2021 at 6:05 pm

It is now common to show the likelihood between two sigma contours as a uniform colour. Why? That contains no more information than just the contours. OK, on a busy plot, as long as you are not colorblind (or want to impress Dick Bond), then colour can help. Fair enough. But in that case, why not colour-code the likelihood, so that one can see not just the contours at some sigma level (which should still be there as well, of course), but rather the likelihood itself? In other applications (CMB map, say), it is common to use a colour bar to represent values of a continuous function.