Description:

Abstract: 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.

Speaker: Alexie Leauthaud, UCSC 

Website: https://alexie.sites.ucsc.edu

Host: Tjitske Starkenburg 

If you know someone who would be interested in attending this talk, please contact Yas Shemirani (yassaman.shemirani@northwestern.edu) to access the Zoom link.

Keywords: Physics, Astronomy, Astrophysics