Connection between dynamically derived IMF normalisation and stellar populations

TL;DR

This study explores how the normalization of the stellar initial mass function (IMF) correlates with stellar population properties in early-type galaxies, revealing complex relationships influenced by age, metallicity, and velocity dispersion.

Contribution

It presents new insights into the connection between IMF normalization and stellar populations using a large galaxy sample and dynamical measurements, highlighting discrepancies with previous low-mass star detection methods.

Findings

IMF normalization varies with age and metallicity indicators.

Accounting for velocity dispersion removes some trends but introduces others.

Weak correlations suggest tension with low-mass star detection studies.

Abstract

In this contributed talk I present recent results on the connection between stellar population properties and the normalisation of the stellar initial mass function (IMF) measured using stellar dynamics, based on a large sample of 260 early-type galaxies observed as part of the Atlas3D project. This measure of the IMF normalisation is found to vary non-uniformly with age- and metallicity-sensitive absorption line strengths. Applying single stellar population models, there are weak but measurable trends of the IMF with age and abundance ratio. Accounting for the dependence of stellar population parameters on velocity dispersion effectively removes these trends, but subsequently introduces a trend with metallicity, such that `heavy' IMFs favour lower metallicities. The correlations are weaker than those found from previous studies directly detecting low-mass stars, suggesting some degree of tension between the different approaches of measuring the IMF. Resolving these discrepancies will be the focus of future work.