ASTR/PHYS 328/428 - HW 6
This HW set consists solely of integrative essays. Each essay should be ~ 1.5 single-spaced pages long, and include good physical descriptions that answer the questions being posed. No equations should be used. Sketches are fine, but don't count towards the length requirements.
1. Describe in detail
pieces of evidence discussed in class that
tell us that *nonbaryonic* dark matter is needed in LCDM. Note: you
*cannot* use galaxy rotation curves or galaxy cluster kinematics to
make these arguments.
2. Describe in detail
three pieces of evidence that tell us that dark
energy is needed in LCDM.
3. Describe three pieces of evidence that the population of galaxies in
the universe has evolved strongly from high redshift (say, z=3) to
today. Explain how this evolution may or may not be consistent with
the conceptual model of hierarchical growth of galaxies. Describe the fundamental difference between the evolution of a galaxy destined to grow up as a spiral like the Milky Way versus one that turns out to be an elliptical galaxy like, say, M87.
4. On one single plot, make a sketch of how the scale factor
with time for the following cosmological models:
Your curves should have the x-axis as t-t0, and at t-t0=0 they should
all have R=R0=1. In other words, all curves should go through the point
need not be perfectly precise, but
should be qualitatively correct relative to one another in shape and
in what time they show R=0. Make sure your sketch shows not only
past, but the future evolution of these universes. And please take the
time to sketch this carefully and neatly, in a way such that the curves
can be differentiated from one another.
- OM=1, OL=0, H0=70 km/s/Mpc
- OM=0.3, OL=0, H0=70 km/s/Mpc
- OM=0.04, OL=0, H0=70 km/s/Mpc
- OM=0.3, OL=0.7, H0=70 km/s/Mpc
- OM=0.3, OL=0, H0=50 km/s/Mpc
- OM=2, OL=0, H0=70 km/s/Mpc
Then for each
explain physically why the curves have the shape they do, how they
depend on the cosmological parameters, and why they give different
values for t(R=0). Also describe and explain physically how structure evolves differently in each universe, including on into the future.