1. TA: David Lin
Office hours:
For help with Cepheid variable lab,
Make an appointment
Discussion section meetings start this week

2. Mpc = 3 million light years
We are here
Approximate direction of 400 km/sec relative to Virgo & Ursa Major Group
Mpc = 3 million light years

3. => After subtracting out 250 km/sec around the Galaxy (can ignore motion in local group), we get a motion with respect to the CMB close to this direction in the Local Super Cluster => it all fits with the CMB being “far away”

4. Where MAP goes “bad”
First Peak
Red model gives 20% to L

5. Update, notice L not needed by CMB yet

6. Get the MAP results first hand in this room, April 18, 2003, at 4:00 p
Get the MAP results first hand in this room, April 18, 2003, at 4:00 p.m. or watch the new papers in early January 2003.
Results could disagree with Supernovae!
Also, Jan 18, same time same place come for same general topic

7. Concept of “Error Bars”:
Any measurement must have an uncertainty assigned to it.
e.g. my mass is [about] 70 kg plus or minus… 0.5 kg.
=>If my mass were to be measured, 67% of the time the reading would be within 0.5 kg of 70 kg

8. <= wrong
right =>

10. Position of first peak tells us the universe is flat!!
But this depends on interpretation
Why is flat or “not” flat such a key (and disturbing) issue?
Remember “flat” => k = 0, W0 = 1; W0 = 1 means relatively (20 times) higher density compared to the density of ordinary matter (as predicted, we see even less)

11. Key to interpretation:
Assume we can calculate angular size of CMB fluctuations

12. Matter and Size of Fluctuations:
Key “buzz word” is Adiabatic
= Light and Matter follow each other
Assume some sound speed in the gas and some ordinary (baryonic) and non-baryonic matter are mixed together WITH LIGHT
Mixed with light means Adiabatic in this context
With this model, calculate the angular size and intensity of the CMB (redshifted light) fluctuations from “acoustic waves.”

13. Observer Angles appear larger for closed case versus open
Photons free stream to the observer on geodesics analogous to lines of longitude to the pole. Thus the same angular scale represents a smaller physical scale in a closed universe Wayne Hu

14. Angles appear even smaller for open case
Acoustic features appear at harmonics of a fixed physical scale at last scattering, the sound horizon. Measurement of the angular scale that such features subtend on the sky can thus measure the curvature of the universe through an angular size distance test. Wayne Hu

15. Adiabatic Fluctuations, cont.
Use theory to match observed galaxies and clusters CMB measurements
Structure formation driven by “seeds”
Can make it all work
In part because the theory is so flexible

16. Keep adding things to make the model agree with observations
Dark Energy
non-baryonic matter (2 kinds)
most of bayronic matter not seen (yet)

17. 300 million light years on a side
What we are looking for!! The “Goldilocks ordinary matter (not too hot and not too cold) so as not to have been detected yet
300 million light years on a side