Remy Indebetouw Discusses His Work in Space Science

Fast Moving Fronts Commentary, March 2011

Remy Indebetouw

Article: The wavelength dependence of interstellar extinction from 1.25 to 8.0 mu m using glimpse data

Authors: Indebetouw, R, et al.
Journal: ASTROPHYS J, 619 (2): 931-938 Part 1, FEB 1, 2005
Addresses: Univ Virginia, Dept Astron, POB 3818, Charlottesville, VA 22903 USA.
Univ Wisconsin, Dept Astron, Madison, WI 53706 USA.
Univ Colorado, Space Sci Inst, Boulder, CO 80303 USA.
(Addresses have been truncated)

Remy Indebetouw talks with and answers a few questions about this month's Fast Moving Fronts paper in the field of Space Science.

SW: Why do you think your paper is highly cited? Does it describe a new discovery, methodology, or synthesis of knowledge? Would you summarize the significance of your paper in layman's terms?

The paper describes a measurement of interstellar extinction at mid-infrared wavelengths. Most of our insight about the universe is gleaned from light emitted by distant objects. That light is absorbed by dust between the source and Earth, and different wavelengths of light are attenuated by different amounts. It is critical to know the wavelength dependence of that "extinction curve" to determine the intrinsic, unattenuated spectrum of any object being studied. The wavelength dependence of the extinction also gives us information about the composition and size of the dust grains themselves, and thus about the physics and processing of interstellar material.

"Although this work is quite detailed and of immediate interest primarily to astronomers, the broader question of how gas and dust are created and processed in galaxies is of general interest to the public."

This paper presents a measurement of the extinction curve at wavelengths between 3 and 10 microns where it had previously been poorly measured, because observations at those wavelengths are very difficult to make from below Earth's atmosphere. The high sensitivity of the Spitzer Space Telescope allowed large parts of the sky to be mapped quickly at those mid-infrared wavelengths, in particular the Galactic Legacy Infrared MidPlane Survey Extraordinaire (GLIMPSE) imaged most of the Milky Way.

Sensitive measurements of many stars in our Galaxy are required to make this extinction measurement, in order to average over variations in the distribution of interstellar material (and resulting attenuation caused by it), and determine the average or universal behavior.

I believe that the high citation rate is in part because the extinction curve is a critical tool for all observers of distant objects, and also because the wavelength dependence that was measured here requires revision of our understanding of interstellar dust, possibly the inclusion of a new population of small grains that had previously not been accounted for.

SW: How did you become involved in this research, and how would you describe the particular challenges, setbacks, and successes that you've encountered along the way?

I worked as a postdoctoral researcher for the GLIMPSE project, with the principal investigator Ed Churchwell at the University of Wisconsin, Madison. I was deeply involved with the data processing and measurement of fluxes for the hundreds of thousands of stars in the images. My interest in interstellar physics and the opportunity to work with one of the world's leading dust experts, John Mathis, also at the University of Wisconsin, motivated me to use the new data to make this new measurement.

SW: Where do you see your research leading in the future?

The measurement has been confirmed independently, e.g., by Flaherty et al. and others.

I am working with graduate student Gail Zasowski and others to refine the measurement, in particular to study whether the wavelength dependence of interstellar extinction varies with location in our Galaxy—the metallicity (fraction of heavy elements present relative to the amount of Hydrogen) of our Galaxy decreases with increasing distance from the center, and the composition and abundance of dust should depend on the metallicity.

Modest changes with Galactocentric radius were published in Zasowski et al. in 2009. Gail Zasowski (ApJ submitted) is also building on these techniques to map the 3D distribution of stars and dust in our Galaxy.

SW: Do you foresee any social or political implications for your research?

Although this work is quite detailed and of immediate interest primarily to astronomers, the broader question of how gas and dust are created and processed in galaxies is of general interest to the public. New stars form from clouds of gas and dust in space, and in their deaths, stars eject new diffuse matter back into their surroundings. This cycle determines the evolution of galaxies, and strongly affects most of our observations and studies of the universe, since all light must travel through that interstellar medium.End

Remy Indebetouw
Assistant Professor
University of Virginia
Charlottesville, VA, USA
Assistant Staff Scientist
National Radio Astronomy Observatory
Charlottesville, VA, USA



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