Connection between dynamically derived IMF normalisation and stellar population parameters

TL;DR

This study investigates the relationship between dynamically derived IMF normalisation and stellar population parameters in early-type galaxies, revealing weak correlations and highlighting differences from spectral analysis methods.

Contribution

It provides empirical analysis of the connection between IMF normalisation and stellar populations using dynamical methods, contrasting with spectral analysis results.

Findings

Old, alpha-enhanced galaxies tend to have heavier IMF normalisation.

Weak correlations between IMF normalisation and [alpha/Fe] or age.

No significant correlation between IMF normalisation and [Z/H].

Abstract

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 Atlas3D project. We study trends between our dynamically-derived IMF normalisation and absorption line strengths, and interpret these via single stellar population- (SSP-) equivalent ages, abundance ratios (measured as [alpha/Fe]), and total metallicity, [Z/H]. We find that old and alpha-enhanced 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 normalisation at a given population parameter. As a result, we find weak IMF-[alpha/Fe] and IMF-age correlations, and no significant IMF-[Z/H] correlation. The observed trends appear significantly weaker than those reported in studies that measure the IMF normalisation via low-mass star demographics inferred through stellar spectral analysis.