Reconciling M/L Ratios Across Cosmic Time: a Concordance IMF for Massive Galaxies

Understand

The stellar initial mass function (IMF) is thought to be bottom-heavy in the cores of the most massive galaxies, with an excess of low mass stars compared to the Milky Way.

• However, studies of the kinematics of quiescent galaxies at 2<z<5 find M/L ratios that indicate lighter IMFs.
• Light IMFs have also been proposed for the unexpected populations of luminous galaxies that JWST has uncovered at z>7, to reduce tensions with galaxy formation models.
• Here we explore 'ski slope' IMFs that are simultaneously bottom-heavy, with a steep slope at low stellar masses, and top-heavy, with a shallow slope at high masses.