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Paper: Upper End IMF Variations Deduced from HI-Selected Galaxies
Volume: 440, UP2010: Have Observations Revealed a Variable Upper End of the Initial Mass Function?
Page: 189
Authors: Meurer, G. R.
Abstract: Much of our understanding of modern astrophysics rest on the notion that the Initial Mass Function (IMF) is universal. Our observations of a sample of HI-selected galaxies in the light of Hα and the far-ultraviolet (FUV) challenge this result. The flux ratio F/fFUV from these star formation tracers shows strong correlations with surface-brightness in Hα and the R band: Low Surface Brightness (LSB) galaxies have lower F/fFUV ratios compared to High Surface Brightness (HSB) galaxies as well as compared to expectations from equilibrium models of constant star formation rate (SFR) using commonly favored IMF parameters. I argue against recent claims in the literature that attribute these results to errors in the dust corrections, the micro-history of star formation, sample issues or escaping ionizing photons. Instead, the most plausible explanation for the correlations is the systematic variations of the upper mass limit and/or the slope of the IMF. I present a plausible physical scenario for producing the IMF variations, and suggest future research directions.
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