NOAO >   Observing Info >   Approved Programs >   2009A-0424

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Proposal Information for 2009A-0424


PI: Julia Greissl, University of Arizona, jgreissl@as.arizona.edu
Address: Steward Observatory, 933 N Cherry Ave., Tucson, AZ 85721, USA

CoI: Michael Meyer, University of Arizona
CoI: Robert Blum, NOAO

Title: Probing the IMF Beyond the Milky Way: Spectroscopy of Two Young Super- Star Clusters in NGC 5253 and NGC4038/9

Abstract: Understanding the origin of the Initial Mass Function (IMF) remains one of the most challenging problems in star formation. What are the physical parameters that control its shape? The stellar IMF has been studied extensively in nearby star-forming regions and studies suggest that it does not vary greatly with initial conditions (Meyer et al. 2000). This leads to the necessity of exploring extreme regions of parameter space not accessible in the Milky Way, to investigate the dependence of the IMF on initial conditions. We propose to obtain high signal-to-noise integrated H- and K-band spectra of massive young clusters in the low-metallicity starburst galaxy NGC 5253 as well as the closest major merger NGC 4038/9 using OSIRIS on SOAR. In these clusters, low-mass stars are still on the pre-main sequence and thus bright enough to be detected through late-type stellar absorption lines in high signal-to-noise near-infrared spectra (Meyer & Greissl 2005) in unresolved stellar populations. Equivalent width ratios tracing low- and intermediate-mass stars will allow us to construct a two-bin IMF and constrain the power-law slope to 0.5 dex within massive star clusters associated with both galaxies.


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



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