On disentangling initial mass function degeneracies in integrated light

The study of extragalactic integrated light can yield partial information on stellar population ages, abundances, and the initial mass function (IMF). The power-law slope of the IMF has been studied in recent investigations with gravity-sensitive spectral indicators that hopefully measure the ratio between KM dwarfs and giants. We explore two additional effects that might mimic the effects of the IMF slope in integrated light, the low-mass cutoff (LMCO) and a variable contribution of light from the asymptotic giant branch (AGB). We show that the spectral effects of these three (IMF slope, LMCO, AGB strength) are subtle compared to age–abundance effects. We illustrate parameter degeneracies and covariances and conclude that the three effects can be disentangled, but only in the regime of very accurate observations, with enhanced effectiveness if high-precision photometry is combined with spectroscopy.