Connection Between Dynamically Derived Initial Mass Function Normalization and Stellar Population Parameters

We report on empirical trends between the dynamically determined stellar initial mass function (IMF) and stellar population properties for a complete, volume-limited sample of 260 early-type galaxies from the ATLAS 3D project. We study trends between our dynamically derived IMF normalization α dyn ≡ ( M / L ) stars /( M / L ) Salp and absorption line strengths, and interpret these via single stellar population-equivalent ages, abundance ratios (measured as [α/Fe]), and total metallicity, [Z/H]. We find that old and alpha-enhanced galaxies tend to have on average heavier (Salpeter-like) mass normalization of the IMF, but stellar population does not appear to be a good predictor of the IMF, with a large range of α dyn at a given population parameter. As a result, we find weak α dyn –[α/Fe] and α dyn −Age correlations and no significant α dyn −[Z/H] correlation. The observed trends appear significantly weaker than those reported in studies that measure the IMF normalization via the low-mass star demographics inferred through stellar spectral analysis.