NOAO >   Observing Info >   Approved Programs >   2011B-0379

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Proposal Information for 2011B-0379


PI: Hongxin Zhang, Lowell Observatory, hxzhang@lowell.edu
Address: Lowell Observatory, 1400 W Mars Hill Rd, Flagstaff AZ 86001, Flagstaff, USA

CoI: Deidre Hunter, Lowell Observatory
CoI: Kim Herrmann, Lowell Observatory
CoI: The LITTLE THINGS team

Title: Deep JH Imaging of the LITTLE THINGS Galaxies: Stellar Mass Assembly in Dwarf Galaxies

Abstract: We propose to obtain deep broadband JH images for 2 dwarf irregular galaxies (dIm) which are part of a larger sample assembled by the LITTLE THINGS project (a VLA Large Proposal). Using the NIR data requested here and other multi-band data we have collected, we will, for the first time, construct high-quality spectral energy distributions (SEDs) covering the whole spectral range of stellar emission for a representative sample of dIm galaxies. dIm galaxies numerically dominate the local universe, yet our understanding of the star formation processes in dIm galaxies is very poor. For example, the star formation rate profile often correlates closely with the stellar surface brightness profile of the older stars, but not with the gas, and we do not know why. Also, abrupt changes in the slope of the stellar exponential profile imply a change in the star formation process at the surface brightness breaks according to some models, but this has not been shown observationally. With the SEDs constructed as a function of radius within each galaxy and our stellar population synthesis technique, we will answer the questions: 1) How is the stellar mass across the disks assembled throughout the lifetime of dwarf irregular galaxies? 2) Are there corresponding surface \it mass density breaks at the surface \it brightness breaks seen in many dIm galaxies? 3) Is there any difference in the stellar populations before and beyond the surface brightness breaks?


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