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How were elliptical galaxies formed, from dwarfs to giants?

I'm reviewing galaxy formation models for my thesis, and the monolithic collapse versus hierarchical merger paradigms seem to give different predictions for ellipticals. Observational data on stellar populations and dynamics in dwarfs versus giants appear to tell conflicting stories. I need a clear synthesis of the evidence to understand if a single mechanism can explain all ellipticals.

 

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By Vishal Answered 1 year ago

From my work comparing simulations to observational surveys, I can say the formation pathway depends critically on mass. For the most massive giant ellipticals, the evidence from their old, metal-rich stars and high central velocities strongly points to a history of major, gas-rich mergers often called "dissipative mergers" that funnel material inward. However, for many lower-mass dwarf ellipticals, I have seen properties consistent with an early, rapid collapse of gas or even the transformation of dwarf irregulars via environmental effects like ram-pressure stripping in clusters. It's not a one-size-fits-all story.

 

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