8.9 Flashcards
1
Q
Composition of the Universe after the first minutes
A
- Plasma with
– p+
– 4He+2
– e- - Radiation
- Neutrinos: hot (relativistic, low mass), weakly interacting
- WIMPS: cold (non-relativistic), weakly interacting massive particles
2
Q
Which component forms the first structures?
A
-
WIMPS, because:
– only feel gravity
– no counteracting gas pressure -
Not plasma or gas because:
– increased T and gas pressure counteracts -
Not relativistic particles because:
– too fast to cluster by gravitation
3
Q
Steps for structure formation before re-combination phase
A
- Dark matter fluctuations from big bang
- Density fluctuation δρ/ρ grows in a matter dominated Universe
- Plasma attracted by dark matter gravity
- Gas pressure causes plasma to bounce back, creating sound waves
4
Q
Evidence from the CMB
what does it show / provide
A
- CMB shows pressure waves with δT/T ≈ 10-5
- provides a map of the dark matter distribution
5
Q
During the dark ages (5)
A
- Dark matter accumulates in growing potentials
- Gas cools and falls into dark matter potentials
- Formation of first stars in proto-galaxies
- Proto-galaxies and quasars start to re-ionize the Universe
- Bright sources trace dominant dark matter distribution
6
Q
Baryonic processes on small scales define:
A
- galaxy structures
- super-massive black-hole evolution
- intergalactic gas properties
- chemical evolution (nucleosynthesis) of the Universe
7
Q
Observational evidence for structure formation?
A
High-redshift observations.
8
Q
Dark energy vs Dark Matter vs Black holes
A
In summary, dark energy is an unknown form of energy causing the accelerated expansion of the universe, dark matter is an unseen form of matter influencing cosmic structures through gravity, and black holes are extremely dense objects with intense gravitational fields formed through the collapse of massive stars.
