Galaxy clusters across cosmic time


I attended this conference in Aix-en-Provence this week. I gave a talk on my hierarchical analysis of galaxy clusters and there was a great turn out from the cluster community but lots of cluster environmentalists! Anyway some of the most interesting talks I found were:

Michael Gregg from UC Davis, gave a really nice talk on some gigantic dust features observed in galaxies infalling in the Coma cluster and believe they were created from the interation between the intercluster medium with the interstellar medium. These structure appear similar to more local structures like the Eagle Nebula but are much much larger and more impressive!

Chris Haines from Arizona University (and previous post-doc at Birmingham)spoke about the newly detected groups infalling onto the LocuSS galaxy clusters. These objects have multi-wavelength follow-up. The X-ray luminosity derived masses suggest that the number density of objects are much higher than that expected from observationally derived cluster mass function suggesting that groups could be biased tracers of the mass distribution.

Fabio Gastaldello who is based in INAF Milano talked about the ongoing problem we have selection functions and in particular the difference in properties of Planck (Sunyaev Zeldovich) detected cluster sample and those detected in X-ray. SZ clusters tend to be deficient in relaxed, cool core objects.

Michael West from the Lowell Observatory gave a lovely talk with many pretty pictures showing the results from his study on the alignment of BCG’s (Brightest cluster galaxies) within superclusters. It seems that the BCG’s are aware of the supercluster/filamentary environment whereas other cluster members are oblivious. They also suggest that AGN within the BCG’s could potentially be aligned with filamentary structure too!

Nicolas Martinet from the University of Bonn presented cosmological results from the KiDS-450 weak lensing peak counts analysis and showed consistent results with the cosmic shear analysis but slightly less in tension with the Planck results. He believes that this method of cosmological analysis should be a much stronger probe of S8 than cosmic shear analysis despite currently having larger uncertainties.