Astroseminar Series - Gerrit Farren - HYBRID

Gerrit Farren is a final year PhD student at the University of Cambridge working primarily on CMB lensing and CMB lensing cross-correlations. Originally from Mönchengladbach in Germany, Gerrit studied at Haverford College in Philadelphia working with Bruce Partridge and Daniel Grin, before moving to Cambridge to pursue his PhD under the supervision of Blake Sherwin. He has previously worked for example on testing axion-like dark matter with the kinetic Sunyaev-Zeldovich effect and shedding light on the Hubble tension through sound horizon-free analyses of galaxy clustering. Gerrit is an active member of the ACT collaboration, and has been serving on the Simons Observatory Collaboration’s Talks Panel for the past year.

Title: The Atacama Cosmology Telescope: Probing the large scale structure with ACT DR6 CMB lensing and cross-correlation with unWISE

Abstract: I will present work on probing the large scale structure of the universe using CMB lensing from the Data Release 6 of the Atacama Cosmology Telescope (ACT) and cross-correlations with galaxies from the unWISE galaxy catalog. My talk will focus on how our highly competitive constraints from CMB lensing and CMB lensing cross-correlations can provide insight into the widely discussed “S8/sigma8 tension”. For this purpose I will briefly introduce the high fidelity CMB lensing reconstruction obtained by the ACT Collaboration and results from the analysis of the lensing auto-correlation. I will discuss new results from the cross-correlation between ACT CMB lensing and unWISE galaxies, highlighting improvements to the analysis pipeline compared to previous work on the cross-correlation between Planck CMB lensing and unWISE by some of my collaborators (Krolewski et al. 2021). I will also show a reanalysis of Planck CMB lensing x unWISE and a joined analysis of the ACT and Planck CMB lensing cross-correlations with unWISE.