Preliminary Exam |
Events During the Week of April 16th through April 23rd, 2023
Monday, April 17th, 2023
- No events scheduled
Tuesday, April 18th, 2023
- No events scheduled
Wednesday, April 19th, 2023
- Reconstruction of the Radial Velocity Field of the Universe with a joint CMB and Large Scale Structure likelihood analysis
- Time: 11:00 am - 6:00 pm
- Place: 4274 Chamberlin
- Speaker: Yurii Kvasiuk, Physics Graduate Student
- Abstract: We develop an optimization-based maximum likelihood approach to analyze the cross-correlation of the Cosmic Microwave Background (CMB) and the Large-Scale Structure (LSS) induced by the kinetic Sunyaev-Zeldovich effect. Our main goal is to reconstruct the radial velocity field of the universe. While the existing quadratic estimator (QE) is statistically optimal for current and near-term experiments, the likelihood can extract more signal-to-noise in the future. Our likelihood formulation has further advantages over the QE, such as the possibility of jointly fitting cosmological and astrophysical parameters. We implement an auto-differentiable likelihood pipeline in JAX, which is computationally tractable for a realistic survey resolution, and evaluate it on the Agora simulation.
- Host: Moritz Muenchmeyer
Thursday, April 20th, 2023
- Unraveling the Dynamics of the Milky Way: Investigations into the Asymmetries of the Galactic Disk
- Time: 11:00 am - 1:00 pm
- Place: 2124 Chamberlin or
- Speaker: Lekshmi Thulasidharan, Physics Graduate Student
- Abstract: "The Radcliffe wave (RW) is a recently discovered sinusoidal vertical feature of dense gas in the proximity of the Sun. In the disk plane, it is aligned with the Local Arm. However, the origin of its vertical undulation is still unknown. This study constrains the kinematics of the RW, using young stars and open clusters as tracers, and explores the possibility of this oscillation being part of a more extended vertical mode. We study the median vertical velocity trends of the young stars and clusters along with the RW and extend it further to the region beyond it. We discovered a kinematic wave in the Galaxy, distinct from the warp, with the amplitude of oscillation depending on the age of the stellar population. We performed a similar analysis in the N-body simulation of a satellite as massive as the Sagittarius dwarf galaxy impacting the galactic disk. When projected in the plane, the spiral density wave induced by the satellite impact is aligned with the RW, suggesting that both may be the response of the disk to an external perturbation. However, the observed kinematic wave is misaligned. It appears as a kinematic wave travelling radially, winding up faster than the density wave matched by the RW, setting its origins into question. If a satellite galaxy is indeed responsible for the presence of this kinematic wave, we predict the existence of a vertical velocity dipole that would be expected to form across the disk. The reality of this prediction may be measurable with the upcoming Gaia DR3 and DR4."
- Host: Prof. Elena D'Onghia
Friday, April 21st, 2023
- No events scheduled