A common aim of my astronomical research is to understand the structure of our own Galaxy, external galaxies, and the universe via parameterized computer models which can be compared directly with observations and catalogs using maximum likelihood analysis.

The Hubble Space Telescope Medium Deep Survey ( MDS ) has been the focus of most of my research since 1992. I have been a co-investigator of this survey project led by Prof. Richard Griffiths which has now been expanded via HST funded archival projects of which I am PI. The MDS database with 2-dimensional maximum likelihood image analysis, of over 200,000 galaxies in over 500 WFPC2 field has been put online via an user searchable interactive web browser interface archive.stsci.edu/mds/. The survey has also resulted in the discovery of many new faint Gravitational Lens Candidates.

After a 1st-class honors B.Sc. degree (1976) from the Dept. of Physics, University of Ceylon, in Colombo, Sri Lanka, my astronomy career started at the University of Pittsburgh where I completed a MS degree (1979) at the Dept. of Physics and Astronomy. I then moved to the Mount Stromlo and Siding Spring Observatories, of the Australian National University. For my PhD thesis (1983), I developed a survey procedure to locate and study the kinematics of in-situ field K-giants in the outer regions our Galaxy, with Ken Freeman as my thesis advisor.

I completed three post-doctoral research appointments. First at the Institute of Advanced Study in Princeton, during 1984/86, Dominion Astrophysical Observatory in Canada during 1986/88 and NASA Goddard Space Flight Center during 1989/91. I joined Space Telescope Science Institute in Spring 1992 to work on the HST-MDS key project and relocated to the Dept. of Physics and Astronomy, Johns Hopkins University in fall 1992 and then to the Dept. of Physics Carnegie Mellon University in fall 1996 with the same group.

I have continued to create computer algorithms and use them for my astronomical research. The increasingly popular trend of using generic software packages does not necessarily get maximum information from the available observations, or produce unbiased estimates of model parameters from an astronomical catalog.

Selected Publications

ApJ = Astrophysical Journal
AJ = Astronomical Journal

Ratnatunga, K. U. Griffiths, R. E. & Ostrander, E. J. 1999, "Disk and Bulge Morphology of WFPC2 galaxies: The HST Medium Deep Survey database" A. J. 118 86-107.

Ratnatunga, K. U. Griffiths, R. E. & Ostrander, E. J. 1999, "The Top Ten List of Gravitational Lens Candidates from the HST Medium Deep Survey" A. J. 117 2010-2023 .

Ratnatunga, K. U., Upgren, A. R. 1997, "Kinematics of Common Dwarf Stars: A Maximum Likelihood Analysis." Ap. J. 476: 811-828.

Ratnatunga, K. U., Ostrander, E. J., Griffiths, R. E., & Im, M. 1995, "New 'Einstein Cross' Gravitational Lens Candidates in Hubble Space Telescope WFPC2 Survey Images." Ap. J. 453 L5-L8.

Ratnatunga, K. U., Griffiths, R. E., Casertano, S., Neuschaefer, L. W., & Wyckoff, E. W. 1994, "Calibration of HST wide field camera for quantitative analysis of faint galaxy images." A. J. 108 2362-2382.

Ratnatunga, K. U., & Yoss, K. M. 1991, "Metalicity and Velocity distribution of Giants towards the Galactic Poles." Ap. J. 377 442-461.

Ratnatunga, K. U., & Casertano, S. 1991, "Absolute magnitude calibration using Trigonometric Parallax: Incomplete, Spectroscopic samples." A. J. 101 1075-1088.

Ratnatunga, K. U. 1990, "Comparison of GSC photometry in three Southern Fields." A. J. 100 280-289

Ratnatunga, K. U., & van den Bergh S. 1989, "The rate of Stellar Collapses in the Galaxy." Ap. J. 343 713-717.

Ratnatunga, K. U., & Freeman, K. C. 1989, "Field K giants in the Galactic Halo II." Ap. J. 339 126-148. 1989ApJ...339..126R

Ratnatunga, K. U., Bahcall, J. N., & Casertano, S. 1989, "Kinematic Modeling of the Galaxy I. The Yale Bright Star Catalog." Ap. J. 339 106-125.

Ratnatunga, K. U. 1988, "Distance independent Study of Moving Groups." A. J. 95 1132-1148.