Research Interests
(1)Theoretical Astrophysics: relativistic jets, accretion disks, MHD
Astrophysical jet near the last stable orbit around a black hole is able to extract the orbital energy most efficiently, where the physics of inner accretion disks plays a critical role. For example, how the disk material is loaded onto the jet in a non-contriving manner? How to get the jet accelerated to a relativistic speed? Can the jet phenomenon exert sufficient torque to make disk accretion?
(2)Cosmology: Sunyaev-Zeldovich effects and gravitational lensing of galaxy clusters, CMB polarization, galaxy formation
SZ effects and gravitational lensing are two complementary probes to reveal a galaxy cluster. SZ probes the intra-cluster baryons and gravitational lensing probes the intra-cluster dark matter. Even a massive gravitationally bound object that has a low galaxy density may also be found by either method. A blind survey with either SZ effect or gravitational lensing can help construct the mass function, which in turn reveals how the large-scale structures of universe formed.
Odd-parity CMB polarization, the so called B-mode polarization, has great importance in early-universe cosmology. The B-mode polarization is extremely difficult to detect, and various methods for extracting the B-mode polarization that is void of conteminations are under consideration, in an attempt to push this area of observational cosmology forward.
Why galaxies form in various sizes? What are the main parameters that determine the scale of galaxy formation? Do mergers of two small galaxies trigger much more active star formation? If so, what parameters control the amount of activities? These are questions under investigation.
(3)Astrophysics Instrumentation: Graphic-card based supercomputer, millimeter-wave interferometer telescope
Can a desktop computer become an IBM Blue Gene? The answer is affirmative for some specific problems, thanks to the advent of GPU in the recent past. For general problems, the major bottleneck is the amount of available memory for computation. Therefore a desk-top supercomputer can only tackle a small problem. To alleviate this bottleneck, we have demonstrated 1GByte/s IO bandwidth from/to the storage devices, leading to a possibility for hard disks to play the role of a memory and to a possibility that a desktop supercomputer can handle a problem needing tera-bytes memory.
Millimeter-wave telescopes are at the forefronts of Radio Astronomy. In terms of frontend devices, millimeter wave detectors can presently be made with solid-state ICs. In terms of integrability, many solid-state ICs can be integrated into a single chip, making the detector highly compact and providing the opportunity to have many compact pixel detectors in one receiver. A prototype multi-pixel receivers are under construction, in collaboration with an electrical engineering team. In addition, NTU-Array located in US has entered its final construction phase. The array consists of six single-pixel receivers, operates at 78Ghz-112Ghz, and employs a high-speed digital correlator to measure the Fourier components of the sky. The science goal of NTU-Array is to detect the SZ effect in the CMB sky.
