Sunshine Coast Centre RASC

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Speaker for 9 October: Arif Babul

At 7:00 PM, 2020 October 9, online on Zoom, the Sunshine Coast Centre of the RASC presents Dr. Arif Babul, whose topic is Probing the Large-Scale Structure of the Universe Using Galaxy Clusters.

Cosmic structures in the universe span a broad range of masses, from dwarf galaxies at the one end of the spectrum to clusters of galaxies at the other.    Clusters of galaxies, the focus on Arif’s talk, are the largest, most massive gravitationally bound objects in the Universe.  They are also the most recent of the cosmic objects to form.   In currently accepted model for the formation of cosmic structure, the increase in the number density of galaxy clusters (i.e., the number of clusters per unit volume) over the recent past, cosmologically speaking of course, depends sensitively on the parameters describing the large-scale geometry and the expansion history of the universe. For this reason, galaxy clusters are regarded as important cosmological probes.    Using clusters as such, however, is not straightforward.  For example, we need to be able to “weigh” them.   Here, Arif will discuss what “weighing them” entails, explain some of the challenges involved,  highlight new insights that Arif and his collaborators were able to bring to the problem, and describe what the resulting cosmological analysis yielded.    One intriguing outcome is that values of the  parameters describing our universe are subtly but non-trivially different from those derived from the cosmic microwave background.   More intriguingly,  this tension may be hinting at new physics.   Arif will speculate about what these might be.  

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