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Chapter 17: Formation of Structure
Terms in this set (34)
a compact group of galaxies
Local group size
2 Mpc diameter
-Abell 1689; a rich cluster
-Lianiakea; the local supercluster
Hubble law used to measure galaxy distances and map large scale structures in universe
Which of the following is mainly
responsible for forming the large-scale structures we see today in the universe?
What is needed to simulate the formation of structures in the Universe?
the level of primordial random density fluctuations, the amount of normal matter/dark matter/dark energy/ radiation and their values of Omegas, an assumption on the properties of the dark matter
-formation of structures in the early universe collapsed to form galaxies
-structure formation is calculated by computer models
-models need the following input;
--amount of matter, radiation, and dark energy
--size of primordial density fluctuations
--dark matter properties
the universe was clumpier on smaller scales than it as on larger scales, so small objects formed first and then grouped together to form larger structures
Further Evidence of Dark Matter
-big bang nucleosynthesis correctly predicts the amounts of light isotopes
-inferred density of normal matter is much less than the density of dark matter
*without dark matter we would not have seen the rich structures in the universe
Dark Matter forms Structures quickly
-dark matter distribution was much clumpier than normal matter because they cannot be smoothed out by radiation pressure
-dark matter provides "seeds" needed to grow structures
Stages of structure formation:
1.Primordial density fluctuations at inflation were inherited by both dark matter and normal matter
2.Gravitational instability led to the growth of dark matter clumps, while normal matter was smoothed with radiation
3. After recombination — normal matter decoupled from radiation field, and started to collapse along with DM halos
4. Normal matter continue to collapse by radiating away energy until disks form, and first stars and galaxies began to form
Galaxies form in Dark Matter Halos/Clumps:
1. at recombination, dark matter clumps exits in uniform background of normal matter/radiation
2. a few million yrs later, gravity slows expansion of dark matter clump
3. within hundred million yrs, clump reaches max size. normal matter has been drawn into clump
4. normal and dark matter collapse until dark matter can't anymore
5. normal matter, which can cool by radiation, continues to collapse; first into stellar clumps
6. the result is a spiral galaxy
Cold Dark Matter
-slows speeds down
-weakly interacting massive particles WIMPS
-less massive candidates; axion and photinos
---works best to form galaxies and large-scale structures we observe today
Which of following structure is the largest?
What does the large-scale structure of the universe look most like?
a sponge with many large holes
What is the method used to measure the distances to the farthest galaxies when mapping out large-scale structures?
redshift and Hubble's law
If the quantum fluctuation imprinted on the dark matter halos at the time of the formation of the cosmic microwave background radiation were 10 times larger, galaxies would likely be:
Why can't dark matter halos collapse to be the same size as the visible parts of galaxies?
dark matter can't dissipate its energy through radiation
Axions and Photinos are examples of?
cold dark matter
Which of the following provides the gravity to form galaxy fragments in the early universe?
cold dark matter halos
What are the ingredients needed to build cosmological simulation of large-scale structure formation?
the density of dark matter and luminous matter int the universe, the spectrum of density fluctuations that quantum mechanics imprints on the early universe, and the density of dark energy in the universe
How much of the total mass of the universe is made up of hot dark matter?
Stars of the first generation were:
more massive than today's average star
What did first generation stars form when the stars died?
The fact that we do not observe any stars with chemical compositions matching our predictions for the very first generation of stars implies:
the first stars died quickly, which implies a high mass
The first galaxies formed:
within dark matter halos
We expect the kinds of galaxies that we see at a redshift of 4 to be?
smaller and much more irregular looking than today
Structure formation of our universe:
proceeds from the bottom and moves up
Which part of the milky way galaxy is the oldest?
What do astronomers believe will be the final state of our universe?
an ever-expanding universe filled with photons and elementary particles
During which era will the final black holes decay
Black hole era
Which era corresponds to the final stage of the universe?
In order from first to last, the specific eras in the history of the universe are known as:
Primordial, stelliferous, degenerate, black hole, and dark era
THIS SET IS OFTEN IN FOLDERS WITH...
Chapter 12:Evolution of Low-Mass Stars
Chapter 15: Our Galaxy, The Milky Way
Chapter 4: Light and Telescopes
Stars chapter 10: Measuring the Stars
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