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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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