I have designed and begun to test a novel technique for rotation-shearing interferometry on single filled apertures (Palomar 5-m and Keck 10-m telescopes), incorporating a 180-degree rotation shear, simultaneous quadrature-phase measurement, and a high-speed, low-noise CCD array. This technique promises to overcome the limitations that have plagued previous rotation-shearing interferometers. I have begun testing this design in the laboratory. In addition to the scientific capabilities of this technique, it is appealing because it is very low-cost and requires relatively little investment of human capital and time to implement.
I propose to continue this investigation, proving the quadrature-phase measurements on astronomical data, and expanding the capabilities of the interferometer to allow differential interferometric observations of the broad emission line regions of active galactic nuclei (AGNs). The differential measurement converts a phase difference between the red and blue wings of the broad H-alpha emission line into an angular displacement. This would be the first direct measurement of the size of broad-line emission regions in AGNs, and one of the first interferometric measurements on any extragalactic object. The quadrature-phase interferometer is uniquely suited to the differential measurement, which could provide positive results on as small an aperture as the Palomar 5-m telescope.
Brian is currently at NASA's Jet Propulsion Laboratory.
My current research has been in the area of modeling synthesis imaging with optical interferometers, studying effects of limited baseline coverage, confusion and noise issues. The other major area of interest has been gas and dust in the Galaxy and beyond. I believe that the Michelson fellowship would be a unique opportunity to work and expand on all these themes of research. After having worked on a variety of theoretical and modeling issues concerned with IR/optical/UV interferometry, my plans for the next stage of my career involve observing with and working on practical aspects of existing interferometers. A considerable part of my graduate school training was spent on implementing and observing with a ground-based single aperture optical interferometer. I believe that ground-based interferometry is currently poised to provide breakthroughs on a number of issues that have been beyond its reach till now. Star formation, structure and evolution of circumstellar disks and planetary systems are all areas with considerable overlap with my research interest in the ISM of our Galaxy and neighboring galaxies. Large apertures, and multiple baselines along with adaptive optics techniques in upcoming instruments like the Keck Interferometer, LBT and VLTI open up imaging and study of extended, moderate surface brightness sources.
Primarily motivated by these considerations, I am applying to take up the fellowship to work with Dr. William Danchi and his collaborators at NASA-GSFC. I describe next how the projects there fit in with my research interest and experience and what I envisage my contributions to be.
There are several exciting ongoing projects being pursued by Dr. Danchi and his collaborators. Of these, I wish to focus on two areas: 1) Multi- wavelength visibility observations of circumstellar material with the Keck interferometer and 2) Design and modeling of a mid-infrared imaging space- based interferometer.
With the existence of "exoplanets" only indirectly established, little is known about their formation, evolution, and physical characteristics. Knowledge of related circumstellars debris disks is similarly uncertain. Direct imaging of exoplanets is given the highest priority in the TPF Architecture Review. The work outlined in this proposal represents some of the initial steps required before TPF's goal of imaging Earth analogs is reached. In particular, the coronagraph being constructed at AMNH for the US Air Force's Advanced Electro-Optical System, a 941-actuator adaptive optics instrument on a 3.6-m telescope, will achieve unprecedented levels of contrast, enabling the first direct probe of companions and disks on solar-system scales and in the sub-brown dwarf mass range. I will make major contributions to the instrument testing, integration, observations and science of the AEOS Coronagraph ("The Lyot Project"), yielding significant advances in exoplanet, brown dwarf, and disk research, and in technologies such as corona graphic occulting mask design, dual-stage adaptive optics and active alignment systems that are crucial to future planet-finding missions. The results of this work will be incorporated into museum exhibits and space shows seen by over 3 million visitors each year.