Universe seen through weak gravitational lensing

Events Calendar

 Time:  Tuesday, December 27, 2022, 02:00pm
 Title:  Universe seen through weak gravitational lensing
 Speaker:  Dr. Mijin Yoon (GCCL)
 Location:  Online via Zoom

ABSTRACT

We are facing an exciting era of discovering the nature of dark matter and dark energy with upcoming large-scale surveys, such as Chinese Survey Space Telescope (CSST), Rubin, and Euclid. One of the major analysis methods of the surveys, weak lensing (WL), uses the shape distortion of background sources for detecting the foreground matter distribution. It is a powerful method for studying dark matter because it can detect matter that does not emit light by itself. By observing the unprecedented depth, it will also be sensitive to the evolution of dark energy. I will introduce my main research topics with WL analysis, which will be expanded and crucial for these surveys.

For the success of precision cosmology, astrophysical/observational systematics should be taken under control. I will discuss WL systematics from baryonic feedback and shape measurement and the mitigation strategies. To mitigate the bias from baryonic feedback, I constrained baryonic feedback amplitude simultaneously with cosmology from WL data for the first time. For better calibration of measured galaxy shapes, I built a new shape measurement pipeline by implementing metacalibration for Kilo-Degree Survey.

I will also present my recent galaxy cluster studies with WL analysis. WL analysis can provide accurate cluster masses without a dynamical equilibrium assumption, which is advantageous for high-z and merging cluster studies. Especially, I would like to highlight the importance of cluster studies for cosmology. For example, the existence of rare massive high-z clusters can challenge the standard cosmological model. Also, merging clusters can be used to reveal dark matter properties when their collisions are reconstructed based on WL masses and multi-wavelength data.


BIO

Dr. Yoon is a senior research fellow affiliated with the German Centre for Cosmological Lensing. She received her PhD in 2016 from the University of Michigan.

As a cosmologist and astrophysicist, her research focus has been on large-scale structure studies through weak lensing and various statistical analysis techniques.  Currently, in a wide-field imaging survey team for cosmology, Kilo-Degree Survey, she is building a new shape measurement/shear calibration pipeline by implementing metacalibration.  With her weak lensing image analysis skills, Dr. Yoon also works on estimating cluster masses for high-z and merging clusters to study cosmology and dark matter properties.  She has simultaneously constrained baryonic feedback effect and cosmology for the first time from the weak leasing survey catalogs (Deep Lens Survey and Kilo Degree Survey), which emphasized the importance of better understanding astrophysical dynamics for future cosmological studies.


Host: Dandan Xu