Han Wang
Welcome!
Hi, I am Han Wang. I come from Xi'an, China, a city rich in history and beauty. I am currently a PhD student at the Max Planck Institute for Astrophysics, working with Prof. Dr. Sherry Suyu, Dr. Aymeric Galan and Dr. Raoul Canameras. I am also a member of the TDCOSMO collaboration.
My research focuses on two areas :
1) Precise measurement of the Hubble constant in the late universe
2) Galaxy evolution, measure dark matter/baryon distribution at relatively small scales
I perform joint strong lensing and dynamical modeling to conduct these two types of studies. I developed a GPU-accelerated joint modeling code based on A. Yıldırım et al 2019, which allows us to efficiently model the lensing systems in the upcoming LSST and Euclid surveys.
Other research interests
Supermassive blackholes: their dynamics and coevolution with galaxies.
Schwarzschild's orbit modeling: I plan to update my dynamics modelling in the current code to improve its handling of slow rotators!
Dark matter: The core-cusp problem. I am interested to see how my measurements can help the theorists in particle physics side.
Galaxy evolution: Baryonic effects and their imprints on the total mass distributions of galaxies.
Programming skills
Proficient in JAX, Python
Basic skills in C, C++
Research Projects (First author paper)
Hubble constant measurement
Multiply lensed sources experience a relative time delay in the arrival of photons. This effect provides an independent method to measure the Hubble constant (H0). However, the lensing potential cannot be uniquely determined from lensing-only modeling. Adding a constant mass sheet on top of the true lens mass leaves many observables invariant, such as image positions and the product of time delays and H0. This phenomenon is known as the Mass Sheet Degeneracy (MSD), and it represents the main source of error in time-delay cosmography.
Combining the stellar kinematics from high spatially resolved NIRSpec IFU data allows us to break MSD and achieve ~4 % precision for H0 measurement from a single lens (H.Wang et al 2024 in prep).
Investigate the mass measurement of the secondary lens
A spiral galaxy at z = 1.49 is lensed by a massive elliptical galaxy at z = 0.68. Simultaneously, it acts as a secondary deflector along the line of sight, deflecting light from sources at higher redshifts ( from z ~2 to 4).
We investigate whether we can constrain the mass of the secondary lens using multi-plane lens modeling and probe it with kinematics (see H.Wang et al 2024 ).
Constraining the multi-scale dark matter distribution in CASSOWARY 31 with strong lensing and stellar dynamics
CSWA 31 is a peculiar lens system. The brightest group galaxy (BGG) is an ultra-massive elliptical galaxy at z = 0.68 with a velocity dispersion of 432 km/s. It is surrounded by group members and several lens arcs probing up to 150 kpc.
We construct the mass model for CSWA 31 using the lensed extended images and the stellar dynamics of the BGG. We find that CSWA 31 is a fossil group, strongly dark-matter dominated towards the center region, and with a projected total mass profile similar to higher-mass cluster-scale halos. The total mass-density slope within the effective radius is shallower than isothermal, consistent with previous analyses of early-type galaxies in overdense environments ( see H.Wang et al 2022 ).
Education
March 2022 - 2025 (expected) PhD candidate Max Planck Institute for Astrophysics, Germany
Technical University of Munich, Germany
Apri 2019 - Nov 2021 Master Technical University of Munich, Germany
Oct 2015 - Dec 2018 Bachelor Karlsruher Institute für Technologie, Germany