Chapter 15 Flashcards
What is an irregular cluster?
A cluster that shows no particular symmetry and consists mainly of spiral galaxies
What is a regular cluster?
A cluster that is roughly spherical or ellipsoidal and are dominated by elliptical galaxies
What is a cluster of galaxy clusters called?
A supercluster
What is top-down structure formation?
The theory that the superclusters formed first and broke down into the smaller galaxy clusters
What is bottom-up structure formation?
The theory that galaxies form first and are drawn to each other by gravity to form clusters and consequentially superclusters.
When did the first stars appear?
Approx. 200mn years after the big bang
What is the significance of finding iron in quasars?
Quasars are among the most ancient things we can see.
Iron is only formed in stars and supernovae
THEREFORE Quasars must have been formed in an environment with stars in it
What is the significance of finding quasars that are part of galaxies?
Proves that galaxies as well as stars must have formed very early after the recombination
What was the nature of elliptical galaxy formation?
The galaxies formed violently, with collisions and mergers before settling into their final form
This helped the stars form quickly
What is it called when nearby galaxies swallow other galaxies
Galactic cannibalism
What is the evidence for the existence of DM?
The rotation speed of the outermost parts of the galaxies was exactly the same as that of the innermost parts of the galaxies
Kepler’s law tells us that this shouldn’t happen, so there must be bunch more mass on the outsides of the galaxy
What is the issue with x ray gas and dark matter?
there is gas contained around certain galaxies that is of sufficient temperature that it would supersede the escape velocity, however it does not
This gas is detected via x rays
There must be a greater mass at hand than in the galaxy
How does gravitational lensing relate to dark matter?
The curvature in the light is greater than the mass of the galaxy in itself would suggest
How does the omega valuation for baryonic matter factor in to DM?
The omega for baryonic matter is higher than what we can see. Therefore, some of the baryonic matter must be dark
