Organized by: Prof. Lu Lu

Events During the Week of May 7th through May 14th, 2023

Monday, May 8th, 2023

No events scheduled

Tuesday, May 9th, 2023

No events scheduled

Wednesday, May 10th, 2023

No events scheduled

Thursday, May 11th, 2023

Gravitational Wave Science with Gamma Rays

Time: 2:30 pm - 3:30 pm

Place: CH4274/https://wipac-science.zoom.us/j/98113285101?pwd=RlNKY2I4Uzg5K2QxVWJmZTJ4eVpWQT09

Speaker: Matthew Kerr , US Naval Research Laboratory

Abstract: The Fermi Large Area Telescope (LAT) has now detected gamma-ray pulsations from over 100 millisecond pulsars, and its <300ns times tamping and nearly-unchanged experimental setup enable high-precision pulsar timing over its 15-year baseline. It is thus a "Gamma-ray Pulsar Timing Array" (PTA). Gamma rays are unaffected by propagation through the ionized interstellar medium, and the high-energy data thus enable the separation of propagation effects from the "spin noise" intrinsic to pulsars, perhaps arising from crustal superfluid turbulence. This capability in turns provides a clean measurement the correlated signals expected to be induced by nHz gravitational waves from merging supermassive black holes. I will compare this approach with radio PTAs and present recent results from the Gamma-ray PTA. In a second part, I will also present an overview and early results from Glowbug, a sensitive gamma-ray burst experiment built at NRL and recently launched to the International Space Station. Its large area and sensitive onboard burst detection algorithm will improve the odds of detecting short gamma-ray bursts associated with neutron star mergers, and its primary mission will completely overlap the O4 observing run of LIGO/Virgo/Kagra.

Host: Ke Fang

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Friday, May 12th, 2023

Probing The Impact of Cluster Weak Lensing Bias On DES Y1 Cluster Cosmological Results

Time: 12:00 pm - 1:00 pm

Place: Chamberlin 5280

Speaker: Johnny Esteves, University of Michigan

Abstract: Over the last two decades of large photometric surveys, optical cluster cosmology has presented a promising way to improve cosmological measurements and our current understanding of dark matter and dark energy. The Dark Energy Survey (DES) Y1 cluster's analysis has revealed a new systematic effect that affects weak lensing measurements, called weak lensing bias. The weak lensing bias arises from the correlation between the mass proxy (such as richness or λ) and the lensing profile for a given mass. The effect is mainly caused by the presence of projected red galaxies along the line of sight, which can bias the mass estimate. However, how this systematic effect impacted the Y1 cosmology is still unclear.

In this talk, I will present a novel forward modeling methodology that was developed specifically for Y3 and outline the technical computing challenges involved in solving multi-dimensional integrals. These challenges have been overcome by utilizing graphics processing units (GPUs), which provide exceptional computational speed and accuracy. In addition, I will present my work on the commissioning of the Rubin Observatory, which will provide invaluable data for advancing our cosmological understanding of the Universe.

Host: Keith Bechtol

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