KIAA postdoc Hassen Yesuf won a PKU Outstanding Postdoc Award, one of 24 granted across PKU, while postdoc Rui Xu won a second 2-year PKU Boya Fellowship. Yesuf is currently a Kavli Astrophysics Postdocotral Fellowship, funded by KIAA, Kavli IPMU, and the Kavli Foundation, while Xu is currently a PKU Boya Fellow with support from KIAA. These prestigious awards are granted to PKU postdoctoral scholars whose research has important scientific significance and academic values or have outstanding economic or social benefits.
Yesuf’s research focuses on applying advanced statistical and artificial intelligence (AI) methods to analyze and interpret multidimensional and complex data of galaxies. One of the major challenges in understanding galaxies has been lack of large samples of hydrogen gas data. While optical images and spectra of about a million galaxies exist, only about 0.1% of them have direct gas information from radio observations. Their method can predict the gas masses of these galaxies using their other observable properties to an adequate accuracy. Furthermore, they also published two application papers that study tens of thousands of galaxies by creatively analyzing gas masses estimated by applying their new method with other data on properties of galaxies. For example, in one of their papers, Dr. Yesuf and Prof. Ho used principal component analysis (PCA) and clustering analysis to track how and why properties of galaxies evolve as their stars age. Their results provide crucial evidence that challenges the current framework of galaxy evolution, and point to the need to revise our understanding of galaxies. In the past two years at KIAA/PKU, Dr. Yesuf published four first-author papers and contributed to three other papers.
Xu’s research focuses on investigating alternatives to general relativity. The standard theory to describe gravity, general relativity, was formulated over a hundred years ago by Albert Einstein. Though general relativity has passed all the tests from terrestrial experiments to astrophysical observations, the existence of dark matter and dark energy are defects that make the theory less satisfactory. Dark matter is necessary if we want to explain the motion of stars in galaxies using the theory, while dark energy is required to generate the acceleration at which our universe expands. Xu investigates a class of scalar-tensor theories that provide explanations for dark matter and dark energy and are motivated by string theory. As the first step in their scheme of testing the scalar-tensor theories, Xu calculated the structure of neutron stars in these theories and predicted the x-ray radiation flux that one might observe using a simple model where neutron stars emit x-ray radiations at certain hot spots on their surfaces. The prediction will be compared with the data from NASA’s Neutron star Interior Composition Explorer mission (NICER). In his first two years at KIAA/PKU, Xu has published four first-author papers and contributed to one additional papers.