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Paper: The Odd Meanderings of the IMF Across Cosmic Time
Volume: 440, UP2010: Have Observations Revealed a Variable Upper End of the Initial Mass Function?
Page: 353
Authors: Davé, R.
Abstract: It is difficult to reconcile the observed evolution of the star formation rate versus stellar mass (SFR-M*) relation with expectations from current hierarchical galaxy formation models. The observed SFR-M* relation shows a rapid rise in SFR(M*) from z=0→ 2, and then a surprising lack of amplitude evolution out to z∼ 6+. Hierarchical models of galaxy formation match this trend qualitatively but not quantitatively, with a maximum discrepancy of ∼× 3 in SFR at z∼ 2. One explanation, albeit radical, is that the IMF becomes modestly weighted towards massive stars out to z∼ 2, and then evolves back towards its present-day form by z∼ 4 or so. We observe that this redshift trend mimics that of the cosmic fraction of obscured star formation, perhaps hinting at a physical connection. Such IMF evolution would concurrently go towards explaining persistent discrepancies between integrated measures of star formation and present-day stellar mass or cosmic colors.
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