Investigating the Nature of Dark Matter with Gravitational Lenses

Prof. Chris Fassnacht (UC Davis) [via Zoom]
Tuesday, April 7, 2020 - 11:00am

The nature of dark matter is one of the major questions facing not only astrophysics, but also high-energy physics.  Our "standard model" of cosmology, Lambda CDM, provides an excellent match to observations of the Universe on large scales, but there are some indications that the model may not adequately reproduce observations on galaxy scales and smaller.  As a result, alternative dark matter models have been proposed to explain the discrepancies.  A powerful way to test these non-CDM models is to determine the statistics of low-mass halos, since some of the models (e.g., warm dark matter) predict fewer halos at low masses than CDM.  In the interesting mass range where the predictions from WDM diverge strongly from those of CDM, halos are expected to host very few to no stars, making their detection difficult.  Strong gravitational lensing provides an excellent complement to Local Group observations, especially because it can detect purely dark halos at even cosmological distances.  In this talk I will discuss two methods of using gravitational lenses to detect low-mass halos and present some recent results, as well as giving some thoughts about future efforts to use these techniques.

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