NOAO >   Observing Info >   Approved Programs >   2004A-0022

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Proposal Information for 2004A-0022


PI: Deidre Hunter, Lowell Observatory, dah@lowell.edu
Address: 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA

Title: The Stellar Edges of Irregular Galaxies: What's Going on Out There?

Abstract: There is considerable interest in, and ignorance of, the outer parts of disk galaxies. Galactic outer edges are the interaction zone between galactic and intergalactic material and are also most sensitive to galaxy-galaxy interactions. Dwarf irregular (Im) galaxies, in particular, may be particularly sensitive to their external environment. Therefore, I am proposing to continue my exploration of the stellar populations in the outer parts of nearby Im galaxies through very deep BV imaging. These data are used to determine how far out various stellar populations extend, how the stars are distributed, and what the star formation history at the edges of irregular galaxies has been. Results so far have been surprising: 1) The starlight continues without an edge well beyond where stars are seen forming today, contrary to predictions of several models; 2) The radial surface brightness profile abruptly changes slope in one galaxy and not in another; and 3) The color remains constant, implying continuous and normal star formation even in the outer parts. I want to see if these unusual features are found in other Im systems.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2004A-0022

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