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under construction

Research

Here is a brief summary of my research activities past and present, with links to some of the relevant papers.

Young Circumstellar Debris Disks
The evolution from primordial disks of gas and dust to debris disks is intimately associated with the formation of planetesimals and planets. However, relatively little is known about the nature of this transition. We are using sensitive IR and sub-mm observations of young stars near Earth to better understand the crucial 10-100 Myr epoch. A highlight from this work is the discovery and characterization of the disk around the young M dwarf AU Microscopii, a low-mass coeval version of the archetypical debris disk system beta Pictoris.

 

Adaptive Optics Imaging of Extrasolar Planetary Systems
Little is known about the substellar constituents in the outer regions of other solar systems. Exploring this domain calls out for direct imaging, as radial velocity and astrometric surveys of these regions are hampered by the very long orbital periods. Adaptive optics (AO) systems on the largest ground-based telescopes (Keck, Gemini, and Subaru) provides a powerful new capability towards direct imging of brown dwarfs and planets around other stars. AO systems correct for the blurring of astronomical images due to the atmospheric turbulence, leading to angular resolution many times better than even the Hubble Space Telescope.  I am leading the the new Gemini Planet-Finding campaign, which will be the largest ground-based program ever devoted to direct imaging of exoplanets.

 

Origins of Brown Dwarfs
Brown dwarfs are now being found in abundance, but their origins remain a mystery. Current and future deep field surveys can place the old field brown dwarf population in the context of the stellar components of galactic structure.  Another potential insight is whether these objects possess circumstellar disks in their youth. We have found that disks around young brown dwarfs are just as common as disks around the higher mass stars.  Finally, we are using new laser guide star adaptive optics systems on large 8-10m telescopes to study brown dwarf binaries with near diffraction-limited imaging in the IR.

 

Surface Brightness Fluctuations
Surface brightness fluctuations (SBFs) of early-type galaxies provide a unique tool for cosmological distance measurements and stellar population studies. We have been pursuing near-IR SBFs measurements using data from a variety ground and space-based telescopes, from as large as the 10-meter Keck Telescope to as small as the 1.3-meter 2MASS telescopes. Our observational efforts have been closely coupled with testing and employing the latest stellar population synthesis models.

 

Formation of Elliptical Galaxies
Elliptical galaxies are key laboratories for understanding galaxy formation and evolution: their high luminosities mean they can be detected at high redshifts (if they exist), and their star formation histories are believed to be simple compared to other galaxies. We have used multi-wavelength measurements of surface brightness fluctuations as a novel probe of recent star formation in early-type cluster galaxies in the local Universe. At high redshift (z~1), spectroscopic studies of extremely red galaxies (EROs) find that some EROs are spatially concentrated, perhaps indicative of young massive clusters.

 


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Last modified on May 11, 2006