Astronomy Professor Chris De Pree Awarded NSF Grant to Study Time Variable Sources of Massive Star Formation

Head shot of Professor of Astronomy, Chris DePree

Charles A. Dana Professor of Astronomy Chris De Pree has been awarded a Research at Undergraduate Institutions (RUI) grant from the Division of Astronomical Sciences, Galactic Astronomy Program of the National Science Foundation (NSF). The $255,233 three-year grant, entitled “Dynamic UltraCompact Ionized Gas regions in the Star Forming Region W49A: Continuing the Search for Flickering Sources,” will enable De Pree and his research students to further their studies of the earliest stages of massive star formation.

Poster describing time variable sources of massive star formation

Understanding the evolution of low mass stars like the Sun is relatively straightforward, because such stars are plentiful and live for billions of years. But high mass stars, like the ones studied in this research, are rare and live for only a few million years, making studies of their early evolution challenging. Early models suggested that when high mass stars were hot enough to ionize the material around them, the gas would quickly expand. New models indicate that as massive stars continue to collect material via their gravitational attraction, the regions of ionized gas around a star may not just grow but also interact with the still infalling material. This interaction will cause regions of ionized gas (also called HII regions) to change (“flicker”) in size and brightness.

De Pree’s recently concluded grant, “Dynamic UC HII regions in Sgr B2: Flickering and Ionized Flows”, which ran from 2012 to 2016, found that a subset of the smallest HII regions in the Galactic center star-forming region Sgr B2 experienced significant changes in brightness on 10 to 20 year timescales. De Pree’s previous NSF grant supported his summer research, and that of seven Agnes Scott students: Katy Butler ’15, Melissa Hutcheson ’15, Kimberly Luong ’15, Ashley Monsrud ’15, Charlee Amason ’17, Kira Fritsche ’18 and Theresa “Terry” Melo ’19. Both Hutcheson and Amason received honorary mentions for their Goldwater Scholarship proposals based on this research.

The success of the previous observational program in detecting changes in Sgr B2 has motivated new observations and analysis of the Galactic W49A star-forming region. In 2014, De Pree and collaborators were awarded sixteen hours of Expanded Very Large Array time to reimage the W49A star-forming region, and these observations have been made over the past year. More recently, this past summer, students Fritsche and Melo worked on making images of W49A from these new observations, partly sponsored by the Goizueta Foundation STEM Scholars Program. This fall, Terry Melo is continuing her summer work to create a radio frequency image of the region to compare to data from 1996.

In January 2017, De Pree and Melo will attend the 229th American Astronomical Society (AAS) meeting in Grapevine, Texas, to present early results. During the period of the newly awarded NSF research grant, the recently completed observations will be compared with observations of W49A made in 1996. The primary goal will be to determine if any of the sources have changed in brightness over the past 20 years and to test theoretical models of the early evolution of high mass stars in the presence of filamentary material. De Pree and his students will use the grant support to carry out research during the summer, to travel to national meetings, and to visit the Very Large Array in New Mexico to utilize the computing facilities and expertise available for data reduction.

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