Accelerated Structure Formation: the Early Emergence of Massive Galaxies and Clusters of Galaxies

Galaxies in the early universe appear to have grown too big too fast, assembling into massive, monolithic objects more rapidly than anticipated in the hierarchical $\Lambda$CDM structure formation paradigm. The available photometric data are consistent with there being a population of massive galaxies that form early ($z \gtrsim 10$) and quench rapidly over a short ($\lesssim 1$ Gyr) timescale, consistent with the traditional picture for the evolution of giant elliptical galaxies. Similarly, kinematic observations as a function of redshift show that massive spirals and their scaling relations were in place at early times. Explaining the early emergence of massive galaxies requires either an extremely efficient conversion of baryons into stars at $z>10$ or a more rapid assembly of baryons than anticipated in $\Lambda$CDM. The latter possibility was explicitly predicted in advance by MOND. We discuss some further predictions of MOND, such as the early emergence of clusters of galaxies and early reionization.