NOAO >   Observing Info >   Approved Programs >   2009B-0084

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Proposal Information for 2009B-0084


PI: Stacey Alberts, University of Massachusetts, salberts@astro.umass.edu
Address: Department of Astronomy, 710 N. Pleasants St., Amherst, MA 01003, USA

CoI: Daniela Calzetti, University of Massachusetts

Title: H(alpha) Observations of Star Forming Regions in XUV disks: Breaking the IMF - Age Degeneracy

Abstract: Tracing the evolution of galaxies is dependent on our understanding of the mechanisms and evolution of star formation, and its dependence on environmental factors. GALEX observations have revealed the existence of extended UV emission beyond the optical disks of spiral galaxies, together with scarce H(alpha) emission in the same locales. These low- density regions are prime candidates for studies of environment- dependent variations of the stellar Initial Mass Function (IMF). We want to investigate whether the sparse outer-disk H(alpha) emission is a consequence of a natural spread in age of the regions responsible for the UV emission or is due to a dearth of massive stars in these low- density regions, similarly to what has been recently suggested for low surface brightness galaxies. In this proposal, we seek to combine deep U, B, V, R, and H(alpha) images with existing GALEX UV and Spitzer IRAC data of the outer disks of NGC0628, NGC2841 and NGC5055, to derive accurate ages of the UV-emitting regions and to compare them with expectations for the ionizing flux, by using U-B colors and spectral energy distributions to constrain the ages and H(alpha) to measure the ionizing photons surrounding the UV regions.


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NOAO >   Observing Info >   Approved Programs >   2009B-0084

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