Sally Oey investigates massive stars and their effects on their host galaxies. One of her interests is whether massive stars can form not only in huge clusters but also more independently. Her group is using spectroscopic data from Magellan to look at the mass and velocity distribution of field massive stars in the Small Magellanic Cloud. These provide clues as to whether the stars formed in relative isolation, or are mostly runaways from clusters. Another interest is the fate of these stars’ ionizing radiation. Since this harsh, UV light isn’t detected directly, Oey’s team is using a new imaging technique to map the transparency of gas in galaxies. This is allowing them to better evaluate the role that ionizing radiation plays in the energy budget of the universe.
Oey has solved a 50-year-old problem on the origin of the so-called Salpeter stellar initial mass function. The ratio in the number of low- to high-mass stars within clusters always shows slightly fewer high-mass stars than would be expected if matter is distributed evenly among all masses. A star cluster forms when a giant molecular cloud fragments; Oey found that the formation of high-mass stars is slightly suppressed if the smallest fragments have less mass than the highest-mass stars. This simple solution agrees perfectly with observations.
AB, Bryn Mawr College; PhD, University of Arizona. Postdoctoral Fellow, Institute of Astronomy/Cambridge, UK; Institute Fellow, Space Telescope Science Institute/Baltimore, MD; Staff Astronomer, Lowell Observatory/Flagstaff, AZ.
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