Holger Israel (AIfA Bonn)

Cosmology with Weak Lensing Clusters: The 400d Survey and Beyond
When Nov 30, 2012 from 10:30 AM to 12:00 PM
What
  • Colloquium
Where SH, Lecture hall
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Galaxy clusters are of particular interest to cosmology: Their mass function, depending on both the expansion history of the Universe and structure formation enables us to constrain cosmological parameters, e.g. the equation-of-state parameter (time variability) of Dark Energy.

Here, I present the current status of the 400d Weak Lensing Programme, following up a sample of relatively distant (0.35<z< 0.90) X-ray selected clusters. Determining cluster masses by weak lensing, we obtain an independent test of the X-ray analyses for the 400d clusters. Once completed, the WL follow-up allows us to cross-calibrate X-ray and WL mass measurements. Such scaling relations will be contributing crucially to next-generation surveys.

I present the analyses for the first eight clusters for which we determined weak lensing masses based on observations with MMT/Megacam, which we demonstrate to be well-suited for weak lensing. Determining masses for all clusters despite unfavourable data conditions, our analyses highlight the capabilities of WL as well as directions for technical improvement. I highlight the case of a cluster seen through a filament, for which we are able to model the massive foreground structure.

Showing the first results for lensing - X-ray scaling relations with our distant sample of "average-mass" clusters, I conclude with an outlook on some of the planned Dark Energy surveys including galaxy clusters and weak lensing.