Chapter 21- Galaxy Birth and Evolution Flashcards
why are their different type of galaxies
conditions of formation and evolution
why does condition of formation of galaxies form different types of galaxies
1) Angular Momentum
- more AM= spiral
- less AM= elliptical
2) Density of original protogalaxy
- high density= formed stars fast= elliptical
- less density= formed stars gradually= spiral
why does collision of galaxies form different types of galaxies
irregulars form when galaxies collide. they turn into ellipticals later on
starburst galaxies
are forming stars so quickly thatchy would use up all their gas in less than a billion years
quasars
- very bright radio sources
- visually look like ordinary stars
- spectrally look very different to stars
- EXTREAME REDSHIFTS
what do galaxies around quasars look like
- sometimes appear to be effected by collisions
- radiation of 1000 galaxies packed into a solar system size object
what can explain all properties of quasars
- gas falling into a supermassive blackhole
- assuming that BH accretes at “Eddington rate”
active galactic nuclei (AGN)
-catchall term for all rapidly accreting black holes in galactic centers (aka quasars, seyferts, radio galaxies, blazers)
bigger galaxies have bigger what
- bigger black holes
- the mass of a galaxies central BH is closely related to the mass of its bulge
- but not all BH’s are actively accreting gas
- BH’s need a source of “food” (supply of gas) for it to be active
what is the food source for BH’s
- galaxy collisions can fuel AGN
- collisions were more communion early universe because things were closer together