Implications of galaxy buildup for putative IMF variations in massive galaxies

Understand

Recent observational evidence for initial mass function (IMF) variations in massive quiescent galaxies at $z = 0$ challenges the long-established paradigm of a universal IMF.

• While a few theoretical models relate the IMF to birth cloud conditions, the physical driver underlying these putative IMF variations is still largely unclear.
• Here we use post-processing analysis of the Illustris cosmological hydrodynamical simulation to investigate possible physical origins of IMF variability with galactic properties.
• We do so by tagging stellar particles in the simulation (each representing a stellar population of $\approx10^{6}~\mathrm{M}_{\odot}$) with individual IMFs that depend on various physical conditions, such as velocity dispersion, metallicity, or SFR, at the time and place the stars are formed.