NOAO >   Observing Info >   Approved Programs >   2007A-0005

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Proposal Information for 2007A-0005


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

CoI: Bruce Elmegreen, IBM T. J. Watson Research Center
CoI: Ed Anderson, NAU

Title: Star Formation at the Stellar Edges of Dwarf Galaxies

Abstract: Dwarf irregular (dIm) galaxies already challenge models of star formation because of their low gas densities even in their centers, but their outer parts present a particularly difficult test of our understanding of the cloud/star formation process. We are proposing to continue our study of the extreme outer parts of dIm galaxies by obtaining very deep B and V images of NGC 4163. We are addressing three questions: 1) Where do dIm stellar disks end? 2) How are stars distributed in the outer regions? and 2) What is the star formation history at the edges? In one dIm system that we observed to (mu)_V=29 mag/arcsec^2, for example, we found that the starlight continues without an edge as far as we can measure it, 2) the radial surface brightness profile changes slope, and 3) the color remains constant throughout the galaxy, implying the same star formation history even to the extreme outer parts. We want to see if these unusual features are found in other dIm systems. Our stellar population studies in the regime of low density stable gas coupled with HI maps, will form a crucial test of a new model of star formation.


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 >   2007A-0005

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