Astr 222 Final Exam Study Questions
Short Answer Questions
(Eight questions total will be on the
final, taken from the list below; they will be worth 5 points each)
- How can globular clusters be used to constrain
the
cosmological
parameters of the Universe? Give an example of a cosmology that is
ruled
out by globular clusters.
- Describe the Fundamental Plane for elliptical
galaxies. Why is it a useful tool for studying galaxies?
- Give a quick rundown on the structure of the
Milky
Way. What
is its size, mass, and luminosity (rough numbers are fine), and what
are the different
structural components?
- Briefly describe what is meant by "Big Bang
Nucleosynthesis". What cosmological parameter does it constrain?
- Describe the general properties of starburst
galaxies and explain how these starbursts might be triggered.
- What is the Tully-Fisher relationship? Describe
how you would use it to get a distance to a galaxy, and what
measurements you would need to make.
- You are studying a galaxy cluster whose
distance you have determined from its redshift, and
you calculate a
virial
mass of 1015 Msun for it. How and why does your answer
depend on
the
Hubble constant? If the Hubble constant was actually 20% larger than
you
thought, how would your answer for the mass change?
- What is the microwave background, and where
does it
come
from?
- Why is a very massive galaxy cluster at z=1 a
problem for OmegaM=1?
- Sketch and label what's going on in the inner
regions of an active galactic nucleus.
- Explain what is meant by a standard candle, and
give two examples of standard candles that can be used to get distances
to other galaxies.
- Describe why we think our galaxy is embedded
in a large "dark matter halo", and why it is hard to determine the
total
mass of the galaxy.
- Sketch the Hubble "tuning fork" diagram and
describe how galaxies are classified this way.
- Describe the differences between the gas in
spiral and elliptical galaxies. How do we detect the gas in these
different kinds of galaxies?
- Describe the evidence for a black hole at the center of our
galaxy. Roughly how massive is this black hole?
- Describe the "winding problem" for spiral arms.
- In a cosmological context, what is meant by "the era of
recombination"?
- What is the difference between hot and cold dark matter, and
how does structure (galaxy clusters and galaxy) grow differently under
these two models?
- Explain the "smoothness problem" and
how the concept of inflation solves this issue.
- Sketch an R(t) plot for universes with a few different
cosmologies (ie different values for H0, OmegaM, and OmegaL). Describe
how and why changing those three parameters changes the plots.
- Describe Cepheid stars and explain why they are
important for studying galactic structure.
- Carefully sketch and describe a merger tree that applies to
the formation of an elliptical galaxy. Do the same for a spiral
galaxy. How do they differ?
- Describe how the population of galaxies in clusters
appears to have changed over time. Why might these changes have occured?
Essay Questions
(Two essay questions will be on the
final, taken from the list below; they will be worth 15 points each.)
- Describe the Supernovae Cosmology Project. How
does
it work,
and what results has it obtained?
- Describe the early history of the Universe from
inflation
to recombination.
- Describe the unified model for quasars and
active galaxies. How does it
explain
differences between Type I and Type II Seyferts? What differences
between
active galaxies does it not explain?
- Describe (in detail) 3 pieces of evidence for
dark
matter
in the Universe.
- Describe how the Universe and the structures
inside it (ie galaxies and galaxy clusters) would have formed and
evolved if
dark matter
were entirely made up of neutrinos. Why can we rule out that scenario?
- Give plausible values for the cosmological
parameters: age,
H0, Omega(Matter), Omega(Lambda). For each, describe two pieces of
evidence which supports
the value you've given.
- Why couldn't the dark matter be all baryonic --
i.e., "normal
matter" that just doesn't shine (say dark clouds of dust, for example).
Give several reasons.
- How can we contrain the value of Omega(Matter)
using galaxy clusters and the large scale structure in the Universe?
Calculations
(There will be three calculation
problems on the final, worth 10 points each. These are not the actual
problems, but they will be similar....)
- A distant galaxy cluster has a velocity
dispersion
of sigma=800
km/s and a half-light radius of 120 arcminutes. It has a average
recession
velocity of 8000 km/s. How far away is it? Use the virial theorem to
show
that the mass of the cluster is ~ 5Rsigma2/G. Calculate the
mass of the cluster.
- If you had a telescope that could detect
objects
down to
mB=22, what is the maximum distance a galaxy could be at if
you wanted to study its globular clusters (which have a typical
luminosity
of LB ~ 6x105 Lsun)?
- You are studying two galaxies which have both
had
Type Ia
supernovae in them. The supernova in Galaxy 1 had a maximum brightness
of mB=12, while the one if Galaxy 2 had a maximum brightness
of mB=15.5. How much further is Galaxy 2 than Galaxy 1? You
do not need to know the absolute maximum magnitude of supernovae Ia to
answer this!
- Use the Friedman equation to calculate the mass
density of
a flat universe without a cosmological constant. If H0=72
km/s/Mpc,
what is the density?