2. What is the Dark Matter?

3. What about “ordinary” non-luminous matter (basically, made from proton, neutrons and electrons)? “Dead stars” (White Dwarfs, Neutron Stars, Back Holes) Planets

4. Increasing Time  (Decreasing Temperature) Mass Fraction  Species Figure: Burles, Nollett, &Turner Nuclei fall out of equilibrium, and freeze out at 75% Hydrodgen, 25% Helium Recall Nucleosynthesis:

5. Theory Data “Baryon Fraction” Nucleosynthesis predicts different abundances depending on the density of ordinary matter. Comparisons with data lead to constraints on the amount of ordinary matter % Helium

6. Using the CMB to learn about the Universe CMB anisotropy power 50 100 solid=inflation model dashed=defect models (magenta=desperate)

7. Characteristic oscillations in the CMB power Adapted from Bennett et al Feb 11 ‘03 WMAP “Active” models Inflation I.1 Successes Temperature Power   Angular scale Fits to CMB data show fix the total amount of “ordinary” matter

8. Supernova Preferred by modern data  Amount of gravitating matter   Amount of “antigravity” matter  (Dark Energy) Red line: No anti-gravity matter Mass-Energy of the a Universe made only out of the “ordinary” matter observed in laboratories Surprise factor CMB, Supernovae and other data tell us about the amount of ordinary and dark matter & energy

9. Preferred by modern data  Amount of gravitating matter  Red line: No anti-gravity matter Mass-Energy of the a Universe made only out of standard model matter  Amount of “antigravity” matter  (Dark Energy) Need to add dark energy here Need to add dark matter here

10. The Upshot: Ordinary matter could only be a small fraction of the total dark matter. (But still worth tracking down) For example: The search for Massive Compact Halo Objects (MACHO’s)MACHO’s

11. Most of the dark matter must be in the form of exotic matter (not yet ever observed in the laboratory).

12. Examples of exotic dark matter: Exotic Neutrinos (different from those observed in the lab). “Weakly Interacting Massive Particles” (WIMPS) [Example UKDM]WIMPSExample UKDM “WIMP-Zillas”

13. Different types of Dark Matter Time  t= today

14. Different types of Dark Matter Time  t= today Theoretical calculations (such as these) of the behavior of dark matter in the universe can be compared with data to test the viability of different theories of dark matter

15. Following slides from: http://cxc.harvard.edu/symposium_2005/proceedings/files/markevit ch_maxim.pdf

16. So far we have talked about explaining rotation curves, lensing data, etc using dark matter What if the laws of gravitational force are different instead?

17. So far we have talked about explaining rotation curves, lensing data, etc using dark matter What if the laws of gravitational force are different instead? This idea is also actively studied, but so far the case has been less compelling.

18. So far we have talked about explaining rotation curves, lensing data, etc using dark matter What if the laws of gravitational force are different instead? This idea is also actively studied, but so far the case has been less compelling. The following slides show the “bullet cluster” data, which many feel make a very strong case for dark matter (vs different laws of gravity). (See also Fig. 22.11 in the text)

19. So far we have talked about explaining rotation curves, lensing data, etc using dark matter What if the laws of gravitational force are different instead? This idea is also actively studied, but so far the case has been less compelling. The following slides show the “bullet cluster” data, which many feel make a very strong case for dark matter (vs different laws of gravity). (See also Fig. 22.11 in the text) Note that in the next slides, all blue and pink colors are the x-rays, and green contours represent that lensing data. This is a different graphing scheme that Fig 22.11.

20. X rays from colliding (“merging”) clusters of galaxies shows hot gas in the clusters (most of the ordinary matter)

21. 1) 2) Optical map from the Hubble Telescope In this image:

22. 1) x-ray map of hot gas (all blue and pink) 2) In this image:

23. The fact that the hot gas is not centered at the center of the contours supports the dark matter explanation. If there was not dark matter, but a different law of gravity instead, what would cause the lensing and why would it be centered away from the hot gas (which is most of the non-dark content of the clusters)? 1) x-ray map of hot gas 2) In this image: