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Studies of stellar populations in early-type galaxies (ETGs) show that themore massive galaxies form earlier and have a shorter star formation history(SFH). In this study, we investigate the initial conditions of ETG formation.The study begins with the collapse of non-rotating post-Big-Bang gas clouds inMilgromian (MOND) gravitation. These produce ETGs with star-forming timescales(SFT) comparable to those observed in the real Universe. Comparing thesecollapse models with observations, we set constraints on the initial size anddensity of the post-Big-Bang gas clouds in order to form ETGs. Theeffective-radius-mass relation of the model galaxies falls short of theobserved relation. Possible mechanisms for later radius expansion arediscussed. Using hydrodynamic MOND simulations this work thus for the firsttime shows that the SFTs observed for ETGs may be a natural occurrence in theMOND paradigm. We show that different feedback algorithms change the evolutionof the galaxies only to a very minor degree in MOND. The first stars have,however, formed more rapidly in the real Universe than possible just from thehere studied gravitational collapse mechanism. Dark-matter-based cosmologicalstructure formation simulations disagree with the observed SFTs at more than 5sigma confidence.

The formation of early-type galaxies through monolithic collapse of gas clouds in Milgromian gravity