My Research Interests:
A. Observational Cosmology:
One of the
fundamental problems in modern cosmology is the question of how galaxies evolved after their formation. There is a considerable evidence to support the view that most galaxies were formed at z < 3 (e.g.
Pascarelle, et al. 1996). However, there is no single consistent theory to explain the diverse morphology of galaxies that we observed nearby and distant parts of the universe. One possible theory to relate
different morphological types is through interaction of galaxies and merging galaxies (Hernquist 1993). A systematic search for interacting galaxies and mergers (galaxies that merged) in deep sky surveys will enable
us to evaluate the importance of interaction and merging to galactic evolution at diferent redshifts.
I have developed a systematic search criterion for interacting and merging galaxies that could directly
apply to deep sky surveys (Kao 2002). Currently, I am studying the evolution of merger rate of galaxies as a probe on galaxy formation and evolution theories. CCSF
students may involve themselves in developing computer algorithms to automatically detect these objects in deep sky surveys (such as the Hubble Deep Field
data set which is in the public domain, and the early-release Sloan Digital Sky Survey data set through colloboration with the University of Chicago, or be directly involved in observations to gather their own data set to analyze. I am planning to obtain observing time in various observatories through different collaborations.
B. Extragalactic Astronomy:
As mentioned previously, interacting and
merging galaxies may have cosmological implication. They do, however, definity have significant evolutionary changes during the process. In order to understand qualitatively the evolutionary process, we need to
study these systems in detail. I have obtained multiband photometric data of a sample of thirty systems of interacting and merging galaxies. Spectroscopic data from ultraviolet to near-infrared will be obtained
through colloboration (with Marianne Takamiya, and others) will be used to constrain chemical evolution, masses (Takamiya, et al. 2001), etc. of these systems.
Students involved in this area of
research will have the opportunity to learn about astronomical spectroscopy through participation in observational runs at observatories and through the analysis of the spectra from these systems.
C. Near-Infrared Studies of the Outer Solar System:
In collaboration with Professor Takeshi Oka at the University of Chicago. I am studying the variation of molecular hydrogen and protonated
molecular hydrogen ion (H3+) emission from spectroscopy and
narrow band imaging. Emission lines from both species are good probes to study plasma conditions in the ionosphere's of Jupiter, Saturn, and Uranus (Miller, Lam, & Tennyson 1994). this project is on going.
Some of the ground-based observations will be carried out at the Apache Point Observatory of the Astronomical Research Consortium and Yerkes Observatory. Students would be able to participate in gathering, reducing and analyzing the data, and do modeling (either the plasma conditions on Jupiter, the
aerosol structure of the atmosphere of Uranus, etc.).
Henquist, L. 1993. "Mergers and the Origin of Early-Type Galaxies". The Environment and Evolution of Galaxies, M. Shull & H. Thronson, Jr., Kluwer Acad. Pub,. p37.
Kao, L., 2002. "The Appearance of High Redshift Interacting and Merging Galaxies", (In preparation for publication)
Miller, S., H. A. Lam, & J. Tennyson 1994.
"What Astronomy has learned from Observation of H3+", Can. J. Phys. 72:760.
Pascarelle, S. M., et al 1996. "Sub-galactic Clumps at a Redshift of 2.39 and Implications for Galaxy
Formation", Nature 383:45.
Takamiya, M., M. Chun, I. Jorgensen, & L. Kao 2001. "Masses of Nearby Galaxies from WIYN IFU Spectroscopy", Proceeding of the Mass of Galaxies at Low and High Redshift.