Connection between Dynamically Derived Imf Normalisation 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 project. We study trends between our dynamically-derived IMF normalisation αdyn ≡ (M/L)stars/(M/L)Salp and absorption line strengths, and interpret these via single stellar population(SSP-) equivalent ages, abundance ratios (measured as [α/Fe]), and total metallicity, [Z/H]. We find that old and alphaenhanced galaxies tend to have on average heavier (Salpeter-like) mass normalisation of the IMF, but stellar population does not appear to be a good predictor of the IMF, with a large range of αdyn at a given population parameter. As a result, we find weak αdyn-[α/Fe] and αdyn−Age correlations and no significant αdyn−[Z/H] correlation. The observed trends appear significantly weaker than those reported in studies that measure the IMF normalisation via the low-mass star demographics inferred through stellar spectral analysis. Subject headings: galaxies: abundances galaxies: elliptical and lenticular, cD galaxies: kinematics and dynamics galaxies: stellar content