The State of the Universe

1. The State of the Universe David Weinberg, Ohio State University

2. The State of the Universe (as we know it) David Weinberg, Ohio State University

3. The State of the Universe (as we think we know it) David Weinberg, Ohio State University

4. Bottom Line • A wide range of current data are well explained by a cosmological model with • A spatially flat Universe • Dominated by cold dark matter and a cosmological constant •  ≈ 0.75, m ≈ 0.25, b ≈ 0.05, H0 ≈ 70 km s-1 Mpc-1 • Gaussian, adiabatic, primordial fluctuations that are approximately (but not perfectly) scale-invariant. • Ongoing/planned experiments will substantially improve the precision of cosmological tests and could poke holes in this picture.

5. How Far We’ve Come • In the mid-’80s, the main data to be explained were: • galaxy clustering • properties of galaxies • existence of high-redshift quasars • upper limits on CMB anisotropy

8. How Far We’ve Come Today: We argue about the parameters of flat inflationary cold dark matter models.

9. The Path to CDM • COBE: Gravitational instability is right, inflation OK.

10. The Path to CDM • COBE: Gravitational instability is right, inflation OK. • Improving galaxy clustering and H0 data: harder to accommodate with m=1.

11. The Path to CDM • COBE: Gravitational instability is right, inflation OK. • Improving galaxy clustering and H0 data: harder to accommodate with m=1. • Ly forest: Explains phenomenon not designed to explain.

12. The Path to CDM • COBE: Gravitational instability is right, inflation OK. • Improving galaxy clustering and H0 data: harder to accommodate with m=1. • Ly forest: Explains phenomenon not designed to explain. • Type Ia supernova Hubble diagram: direct evidence for cosmic acceleration. Riess et al. 1998

13. The Path to CDM • COBE: Gravitational instability is right, inflation OK. • Improving galaxy clustering and H0 data: harder to accommodate with m=1. • Ly forest: Explains phenomenon not designed to explain. • Type Ia supernova Hubble diagram: direct evidence for cosmic acceleration. • BOOMERANG/MAXIMA: Flat universe, clear acoustic peak. Strengthens supernova evidence for dark energy. Jaffe et al. 2001

14. Developments since 2000 • Substantial improvements in precision and dynamic range of measurements (WMAP, DASI, CBI, ACBAR; 2dFGRS, SDSS; larger and more distant supernova samples; precise Ly forest measurements) • Addition of: Weak lensing, CMB polarization, CMB/BBN consistency on b. • “Vanilla” CDM, with tot=1, w=-1, free parameters m, b, h, ns, As, looks close to consistent with all current data, though some tension on parameter values.

15. Dark Matter • The Silver Bullet Cluster: qualitatively new evidence for dark matter vs. modified gravity.

16. Clowe et al. 2006; fig. courtesy Doug Clowe

17. Dark Matter • The Silver Bullet Cluster: qualitatively new evidence for dark matter vs. modified gravity. • Small scale problems of cold dark matter: • Excess of small scale structure (satellite galaxies). • Wrong rotation profiles of disk galaxies. • My take: The case that these problems are related to dark matter not baryonic physics isn’t strong enough, and probably won’t become so. • Ly forest lower limit on dark matter particle mass: 2.5 keV for thermal equilibrium decoupling, 14 keV for sterile neutrino (95% confidence; Seljak, McDonald, & Trac 2006)

18. Ly forest flux power spectrum: cold dark matter vs. 6.5 keV sterile neutrino Seljak, Mcdonald, & Trac 2006 (astro-ph/0602430)

19. WMAP l ≈ 100 degs /  Spergel et al. 2006

20. WMAP 3-yr data vs 1-yr data: Smaller error bars throughout. Key difference is new polarization measurement, changing central value and error bar on optical depth. Changes central values on m and 8: a lighter, less clustered universe. Substantially reduces degeneracies among cosmological parameters. Spergel et al. 2006

21. WMAP + SDSS LRGs SDSS adds turnover scale, tilt, and acoustic oscillation scale measured in km/s at z ~ 0.35. Tegmark, Eisenstein et al. 2006

22. WMAP + SDSS LRGs Tegmark, Eisenstein et al. 2006

23. WMAP + SDSS LRGs Tegmark, Eisenstein et al. 2006

24. WMAP + SDSS LRGs Tegmark, Eisenstein et al. 2006

25. Supernova Hubble Diagram Riess et al. 2004 Astier et al. 2006

26. Supernova Hubble Diagram + SDSS BAO Scale Astier et al. 2006

27. Developments since 2000 • Substantial improvements in precision and dynamic range of measurements (WMAP, DASI, CBI, ACBAR; 2dFGRS, SDSS; larger and more distant supernova samples; precise Ly forest measurements) • Addition of: Weak lensing, CMB polarization, CMB/BBN consistency on b. • “Vanilla” CDM, with tot=1, w=-1, free parameters m, b, h, ns, As, looks close to consistent with all current data, though some tension on parameter values.

28. Game Over?

29. Game Over? The tyranny of vanilla: Will we be cursed by a successful standard model with key elements that we don’t understand?

30. Game Over? • Things we might find with improved data: • w = -0.9 • w = -1.1 • dw/dz|0.5 = 1, or (z=10) = 0.1. • Inconsistency of gravitational and distance constraints on w: modified gravity, not dark energy. • tot = 1.02 • r = 0.1 (gravity waves), dns / d ln k = -0.03 • Primordial fluctuations have non-Gaussian or isocurvature component

31. Future Experiments Improved measurements of supernovae, weak lensing, galaxy clustering/baryon oscillations, Ly forest, CMB temperature and polarization anisotropies An incomplete list: Current: SDSS-II, CFHT Legacy Survey Near Future: PAN-STARRS, Planck, South Pole Telescope Medium Term: Dark Energy Survey, SDSS-III Long Term: LSST, Square Kilometer Array, JDEM, CMBPOL

32. Bottom Line • A wide range of current data are well explained by a cosmological model with • A spatially flat Universe • Dominated by cold dark matter and a cosmological constant •  ≈ 0.75, m ≈ 0.25, b ≈ 0.05, H0 ≈ 70 km s-1 Mpc-1 • Gaussian, adiabatic, primordial fluctuations that are approximately (but not perfectly) scale-invariant. • Ongoing/planned experiments will substantially improve the precision of cosmological tests and could poke holes in this picture.