KICP Colloquium:  Alexie Leauthaud (University of California, Santa Cruz)

3:30–4:30 pm Zoom

Alexie Leauthaud (University of California, Santa Cruz) "Cosmology, Correlations, and Conundrums"

I will begin this talk with an overview of galaxy-galaxy lensing and how it informs us about the connection between galaxies and their dark matter halos. I will then present a variety of new results in this field. First, I will discuss the “lensing is low” effect whereby the lensing signal around massive galaxies has a lower amplitude than predicted based on the galaxy auto-correlation function from BOSS. I will present some new updates on this topic and discuss the cosmological implications of this effect. I will further present “Lensing without Borders”, an inter survey collaborative effort to empirically test the accuracy of galaxy-galaxy lensing measurements in current day surveys. I will also present new results suggesting that the light from central galaxies is a much better tracer of halo mass than previously recognized and I will discuss how this effect might be used to improve optical cluster finding algorithms. Finally, I will present the Merian survey: a new program that will use 60 nights on the Blanco telescope and two custom made filters to detect 100,000 dwarf galaxies and measure their halo masses via gravitational lensing.

Event Type


Jun 2