Chapter 21- Galaxy Birth and Evolution

Question 1

why are their different type of galaxies

Answer 1

conditions of formation and evolution

Question 2

why does condition of formation of galaxies form different types of galaxies

Answer 2

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

Question 3

why does collision of galaxies form different types of galaxies

Answer 3

irregulars form when galaxies collide. they turn into ellipticals later on

Question 4

starburst galaxies

Answer 4

are forming stars so quickly thatchy would use up all their gas in less than a billion years

Question 5

quasars

Answer 5

• very bright radio sources
• visually look like ordinary stars
• spectrally look very different to stars
• EXTREAME REDSHIFTS

Question 6

what do galaxies around quasars look like

Answer 6

• sometimes appear to be effected by collisions

- radiation of 1000 galaxies packed into a solar system size object

Question 7

what can explain all properties of quasars

Answer 7

• gas falling into a supermassive blackhole

- assuming that BH accretes at “Eddington rate”

Question 8

active galactic nuclei (AGN)

Answer 8

-catchall term for all rapidly accreting black holes in galactic centers (aka quasars, seyferts, radio galaxies, blazers)

Question 9

bigger galaxies have bigger what

Answer 9

• 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

Question 10

what is the food source for BH’s

Answer 10

• galaxy collisions can fuel AGN

- collisions were more communion early universe because things were closer together