PHYS 005 Lecture Notes - Lecture 12: Star Formation, Bullet Cluster, Gravitational Lens
5 Jul 2018
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5/02- Session 12 Colliding and Evolving Galaxies
Ch. 24 Sections 7,8,9
Redshift
z= ƛ-ƛ0/ƛ0
ƛ- expected unshifted wavelength of light
ƛ0- observed shifted wavelength of light
●Equivalent to LOOK BACK TIME
○How far in the past we’re looking at the object
○Look back time changes
as the proportions of dark matter, baryonic matter, dark energy
change
Colliding Galaxies
●Dominant gravitational force fr another area- ex. Bigger galaxy pulls smaller galaxies
●STARS DO NOT COLLIDE
○Distance btw stars & stars are so tiny that they rarely collide
●GASES COLLIDE- bc they are spread out
○Gas collisions FORM STARS
○Get super hot due to friction- emit x-rays (from clouds straight to x-ray)
■Only way in universe that we make gas hot-> CAN’T MAKE STARS if they’re too
hot to collapse
Starburst Galaxies
●Depend on LESS VIOLENT collisions to FORM STARS
●Merging galaxy
●Surrounded by warm dust- most luminous when looked through infrared
Tidal Forces & Galactic Mergers
●Don’t have to collide, flybys- pass by very closely to another galaxy and touch it
○Makes tidal forces- gravitational pull that acts on THINGS THAT AREN’T SOLID- (galaxies)
■Similar to what moon & sun does
○Disturb & change things, BUT DOESN’T RIP APART
●Evidence of past collisions
○Sticky evidence- trails of gas emission
■Streams of hydrogen
○**close flybys may also be a 3rd way to make SPIRAL ARMS
●Colliding galaxies can end up merging together *depends on how fast it’s going
Milky Way & Andromeda will collide in 4 billion years
●Andromeda makes more gravity & pulling us toward them (5x bigger than us)
●Final product: older elliptical
galaxies w. red/yellow stars
Document Summary
How far in the past we"re looking at the object. Look back time changes as the proportions of dark matter, baryonic matter, dark energy change. Dominant gravitational force fr another area- ex. Distance btw stars & stars are so tiny that they rarely collide. Gases collide- bc they are spread out. Get super hot due to friction- emit x-rays (from clouds straight to x-ray) Only way in universe that we make gas hot-> can"t make stars if they"re too hot to collapse. Depend on less violent collisions to form stars. Surrounded by warm dust- most luminous when looked through infrared. Don"t have to collide, flybys- pass by very closely to another galaxy and touch it. Makes tidal forces- gravitational pull that acts on things that aren"t solid- (galaxies) Disturb & change things, but doesn"t rip apart. Similar to what moon & sun does. **close flybys may also be a 3rd way t o make spiral arms.
