monolithiccollapse

Monolithiccollapse is a term used in astrophysics to describe a theoretical scenario in which a large gas cloud collapses rapidly and coherently to form a bound stellar system, such as an elliptical galaxy or a dense star cluster, in a relatively short timescale. In practice the more common spelling in the literature is monolithic collapse, but the variant monolithiccollapse appears in some online and simplified sources.

Historically, the concept was proposed to account for the old, metal-rich stellar populations and the smooth, spheroidal morphologies observed in many elliptical galaxies. The basic mechanism involves rapid dissipative collapse of gas, intense bursts of star formation, and subsequent feedback that quenches further activity. A characteristic prediction is a strong chemical enrichment in a short period, leading to metallicity gradients with more metal-rich inner regions.

Observational evidence cited in support of monolithic collapse includes early-type galaxies that exhibit old stellar ages, alpha-element enhancement consistent with rapid star formation, and metallicity gradients. However, many galaxies show signs of later accretion and mergers, suggesting that formation histories are diverse and often facet of hierarchical growth.

Modern cosmology largely favors hierarchical assembly within the Lambda-CDM framework, where galaxies grow through the merging and accretion of smaller systems. Monolithic collapse remains a useful simplifying model for explaining rapid star formation episodes and certain chemical abundance patterns observed in some systems, even as it coexists with more complex, merger-driven formation pathways.