Early Galaxy Formation and the Hubble Constant Tension

Abstract

Tension between local determinations of the Hubble constant and the value found in fits to the cosmic microwave background (CMB) acoustic power spectrum have emerged as finer angular scales (higher multipoles ℓ) have been measured in the latter. Independent observations indicate that massive galaxies emerged at higher redshift than anticipated in the standard ΛCDM structure formation paradigm. If genuine, these early galaxies would cause excess gravitational lensing of the CMB, adding an anomalous source of power at high ℓ. I suggest that accommodating this anomalous source of power in multiparameter fits might be the root cause of the Hubble tension rather than systematics in local measurements.