Constraints on the Field Star IMF from Resolved Stellar Populations based Star Formation Histories

TL;DR

This study uses HST observations of nearby galaxies to assess how well star formation histories derived from color-magnitude diagrams can constrain the stellar initial mass function, finding limited sensitivity to IMF variations.

Contribution

It demonstrates that CMD-based star formation histories have a broad minimum with respect to IMF slope variations, indicating weak constraints on the IMF from this method alone.

Findings

CMD-SFH fitting shows minor changes with IMF slope variations

Broad minimum in parameter space indicates weak IMF constraints

Resolved stellar populations can complement other methods to study IMF variations

Abstract

Using HST/ACS observations of resolved stellar populations in nearby galaxies, I explore the constraints one can place on the field star IMF from star formation histories (SFHs) derived from synthetic color-magnitude diagram (CMD) fitting. In particular, I show how reasonable variations in the slope of the IMF, relative to a Salpeter slope, lead to only minor changes in the SFHs. This shows that CMD-SFH fitting parameter space has a broad minimum with respect to IMF variations and implies that CMD based SFHs can only provide weak explicit constraints on the stellar IMF. However, observations of resolved stellar populations in dwarf galaxies can be used to tandem with other methods to search for variations in the upper IMF.