AST-0707563/0707426/0707468/0707835 Hunter/Elmegreen/Simpson/Young
This is a collaborative project led by Dr Deidre Hunter of Lowell Observatory, along with Dr Bruce Elmegreen at the IBM Thomas J. Watson Research Center, Dr Caroline Simpson of Florida International University, and Dr Lisa Young from the New Mexico Institute of Mining and Technology.
The team will obtain and analyze high angular and velocity resolution neutral hydrogen interferometric data of dwarf irregular galaxies and combine these with their extensive optical, ultra-violet, and infra-red images, in order to determine how these galaxies form star-forming gas clouds that propel their evolution. This study will lead to an improved understanding of star formation in all disk galaxies, by addressing a number of questions: what regulates star formation in small galaxies; what is the relative importance of sequential triggering; what regulates turbulence; how important is triggering by random turbulence; what is happening in the far outer parts of dwarf galaxies; what aspect of star formation changes in blue compact dwarf galaxies? These questions need to be answered because dwarf galaxies are the most common galaxy, the most pristine chemically, and the type most closely connected to the earliest star-forming systems in the universe.
High school students, undergraduates, graduate students, and post-doctoral researchers have been, and will continue to be, involved in this journey of scientific discovery. Many of these participants have in the past been women, and some were also from under-represented groups. The team will continue this preference. The investigators are all also involved in continuing public and K-12 outreach activities.
Most galaxies are continually recycling and reinventing themselves as they form new stars out of cold gas -- the same process that is going on, for example, in the Orion Nebula in our own Galaxy. In the neighborhood of our Galaxy there are also dozens of very small dwarf galaxies, and the essence of the LITTLE THINGS project has been to study how gas turns itself into young stars in these dwarf galaxies. In many respects they are probably quite similar to the very first generation of galaxies which formed early in the universe, and a greater understanding of the star formation process in local dwarf galaxies should also give insights into how the first galaxies came to be. The data obtained for this project include more than 400 hours of observing time with the National Radio Astronomy Observatory's Very Large Array (VLA) radio telescope, covering 41 dwarf galaxies, plus data from optical telescopes and the GALEX ultraviolet satellite telescope. A significant effort from the team involved the complicated process of making gas maps out of the VLA data, and this effort has now produced the largest existing collection of high quality, high resolution gas maps for local dwarf galaxies. The gas maps are also coupled with optical and ultraviolet images which reveal the locations of stars of various ages, giving the past histories of star formation activity in the dwarf galaxies. These results are being used to try to understand why some galaxies have much higher rates of star formation than others. Team members are working through several techniques to measure temperatures and densities in the gas, as colder and denser gas ought to form stars more effectively. They are also studying the internal structure of the gas, as young stars sweep out voids or bubbles and cause noticeable turbulent, stirring motions in the gas. They are measuring the effects of elemental abundances (chiefly carbon, nitrogen, and oxygen) on the properties of the gas and on its ability to form stars. Finally, they are using the velocities of gas and stars to measure the gravitational fields of the galaxies and to compare the inferred quantities of dark matter to theoretical models of galaxy formation. The data and maps produced in this project are now available online, and they should serve as a legacy resource for the entire astronomical community. Future work by others using these resources will undoubtedly include projects that the team hasn't even thought of yet. The quality of these gas maps in dwarf galaxies are not likely to be superseded for a decade or more. NSF funding for this project directly supported four graduate students and one postdoctoral researcher. It also enabled the team to engage in collaborative work between their host institutions and colleagues at the National Radio Astronomy Observatory, Universidad de Chile, University of Hertfordshire (UK), and CEA Saclay (France), among others. Team members were able to provide research experiences for seven undergraduate students. They also conducted an extensive outreach program for 5th to 8th graders through the Lowell Observatory Navajo-Hopi Astronomy Outreach Program, which includes visits of astronomers to classrooms in rural Arizona, as well as visits by the students to Lowell Observatory.
