Jonathan Elias

Tucson Nighttime Scientific Staff


Areas of Interest

Star Formation and Evolution, Magellanic Clouds

Recent Research Results

Elias's most recent research project has been an investigation of stellar mass loss in the Magellanic Clouds. In the later stages of their evolution, stars become red giants and lose mass. As material flows out from the star, it cools and dust forms. The dust is detectable at infrared wavelengths; if there is enough of it, it will also hide the star itself from view. The abundance of dust in the circumstellar material and the rate and velocity of mass loss may all depend on the abundance of heavy elements in the star losing mass -- but it is not known in which ways. In order to see what actually happens, it is necessary to compare observations of stars with different heavy element abundances. As stars in the Magellanic Clouds have lower abundances than similar stars in the Galaxy, and since these galaxies are close enough for individual stars to be readily observable, they provide a useful basis for comparison.

Future Research Plans

Elias's work to date shows that the data are consistent with the hypothesis that only the amount of dust depends on the heavy element abundance, and that the two are directly proportional, while the overall mass loss rate is insensitive to abundance variations. Other workers suggest, though, that mass loss rates should be lower in stars with lower heavy element abundances. Few Magallanic Cloud mass-losing stars have been identified, especially in the Small Magellanic Cloud, so the evidence does not strongly favor one hypothesis over the other. Elias will be obtaining data from the Infrared Space Observatory (ISO) on selected regions of the Large and Small Magellanic Clouds. The new data will provide much larger samples of mass-losing stars than have been available up to now, and should settle the issue.

Service

Elias's primary service activities during the last year have been in several areas. He began serving officially as project scientist for the Gemini Near-Infrared Spectrometer (GNIRS) in March 1995, and transferred from Chile to Tucson in January 1996 as a consequence. This position also entails service on the Gemini Infrared Instrumentation Science Working Group. In addition, he was one of the three scientific staff members responsible for the CTIO infrared program up until his departure. He also acted as the CTIO telescope scheduler, and was a member of the CTIO Time Allocation Committee, the CTIO Advisory Committee on Technical Resources (which provides scientific oversight of the CTIO instrumentation program) and the NOAO Instrument Projects Advisory Committee (which performs similar functions for NOAO as a whole). His membership on IPAC has continued after his transfer to Tucson. He has also been involved with review of CTIO's cost structures.


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Posted: 06Dec1996