ASTR-1010 Lecture Notes - Lecture 18: Disk Density, Galaxy Formation And Evolution, Solar Mass
6 Oct 2016
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Observing galaxies at different distances shows how they age. Our best models for galaxy formation assume that matter originally filled all of space almost uniformly and gravity of denser regions pulled in surrounding matter. H and he gases in these clouds formed the first stars. Supernova explosions from first stars kept much of the gas from forming stars. Leftover gas settled into . (keivan changed the damn slide) Spin: initial angular momentum of protogalactic cloud could determine size of resulting disk. Density: elliptical galaxies could come from dense protogalactic clouds that were able to cool and form stars before gas settled into a disk. We must also consider the effects of collisions. Collisions were much more likely early in time, because galaxies were closer together. Many of the galaxies we see at great distances (early times) indeed look violently disturbed. Modeling such collisions on a computer shows that two spiral galaxies can merge to make an elliptical.
