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The significance of s 8 and W m measurements

The significance of s 8 and W m measurements. Sarah Bridle, IoA, Cambridge. Current status of s 8 , W m plane Importance of study Future non-velocity work -> s 8 , O m Some questions. The two structure formation parameters:. W m = density of the universe dark + baryonic matter

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The significance of s 8 and W m measurements

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  1. The significance of s8 and Wm measurements Sarah Bridle, IoA, Cambridge • Current status of s8, Wm plane • Importance of study • Future non-velocity work -> s8, Om • Some questions

  2. The two structure formation parameters: Wm = density of the universe • dark + baryonic matter • in units of the critical density s8 = clumpiness of the universe • rms fluctuation in 8 Mpc spheres • present day (z=0) • calculated from linear theory prediction

  3. WMAP results

  4. WMAP is a massive improvementFix H0=72, Wbh2=0.02, ns=1, Wk=0, zre=17 • Pre-MAP • WMAP + l>800 data (VSA, CBI, ACBAR)

  5. Which parameters?Allow H0, Wbh2, ns to be free • Contours balloon

  6. Which parameters?Has a big effect on the error bars... Bridle, Lahav, Ostriker & Steinhardt (2003) Science

  7. Cluster counts: results summary

  8. Cosmic shear: results summary • comparison of latest results plot

  9. Bridle, Lahav, Ostriker & Steinhardt (2003) Science

  10. Feldman et al astro-ph/0305078

  11. Why is this important? • Cosmology not 'solved' if errors ~ 30% • Many data sets cross in s8, Wm plane • agreement tests the model • Implications for other parameters: • non-Gaussian primordial perturbations • shape of primordial power spectrum • neutrino mass

  12. Take 3 data sets...

  13. Compare XLF with CMB+2dF+fgas Allowing free mn Allen, Schmidt & Bridle astro-ph/0306386 Assuming mn=0 • non-zero mn fits better • non-zero mn fits better • non-zero mn fits better

  14. CMB + 2dF + fgas + XLF -> mn • ~1.5 % of Wcrit • ~5 % of Wm • mn=0.21 eV • Use Wnh2= 3mi / 94eV Allen, Schmidt & Bridle astro-ph/0306386

  15. The future of other probes • Cluster counts • need M-T calibration • CMB • limitation is in extrapolation to 8 Mpc • tells us about other parameters eg. mn • Cosmic shear • psf removal is dominant question • but SNAP should solve most problems...

  16. Questions about 6dF-> s8, Wm • What uncertainty levels on s8, Wm ? • which statistics to use? (v12, Pv(k)) • Treatment of non-linear effects • Calibration and reliability of Dn-s

  17. 'Competition' with cosmic shear • Need checks on cosmic shear systematics • Velocities cf density -> tests gravity law • Redshift evolution of fluctuations useful? • Velocities z < 0.05 • Cosmic shear z > 0.2 • Helps to constraining recent w(z) +? • High resolution in z -> ? • helps with cluster masses...?

  18. Conclusions • CMB alone cannot constrain s8, Wm well • Clusters cf cosmic shear -> need checks • Feldman et al results look v promising • What will the random and systematic uncertainties from 6dFv on s8, Wm? • How interesting will this be cf. eg. cosmic shear?

  19. END

  20. Effect of mn on cosmology • CMB affected very little • Supress growth of fluctuations on small scales • Matter power spectrum: • multiplied by ~0.7 • on scales <~10 Mpc

  21. Particle physics -> mn • Standard model -> mn=0 • mne < 2eV (95% confidence) • laboratory tritium-b decay • mM < 0.35 eV (90% confidence) • effective Majorana mass • neutrinoless double-b decay • Dm212Y0.012 eV2 Dm322Y0.052 eV2 • Solar, atmospheric oscillations

  22. Recent cosmology -> mn • Assuming 3 neutrinos of degenerate mass: • (See Hannestad 2003, Pierpaoli 2003 for nn) • mn < 0.23 eV (95%) • Spergel et al 2003: CMB+2dF+Lyman-a • mn<0.14 eV (68%) • Lewis & Bridle 2002: CMB+2dF+HSTKP+BBN+SN • mn < 0.73 • Elgaroy et al 2002: 2dF+ weak priors

  23. Dependence on assumptions Without tensors Without 2dF

  24. CMB constraints • low-ð amplitude • s8, Wm, WÉ, tensors • 1st peak height • Wmh2, s8e-t • 2:1 peak heights • Wbh2, n • 3:1 peak heights • n • 1st peak position • WK, w, Wbh2, t0 • low-ðTE amplitude • zre

  25. Weighing the neutrino using the CMB and galaxy clustersAllen, Schmidt & Bridle 2003 • A non-negligible neutrino mass is preferred! • Implies mn=0.21G0.11 eV (1s) per species • Assumes • w=-1, nrun=0, Wk=0 • Can rely on clusters.. - CMB+2dF+fgas - CMB+2dF+fgas+XLF

  26. Post WMAP: Remaining questions • Is the current cosmological model correct? • What happened in the early universe? • What is the dark matter? • What is the dark energy? But also simpler questions remain...

  27. Feldman et al astro-ph/0305078

  28. Feldman et al astro-ph/0305078

  29. Combining CMB and galaxy cluster observations • Galaxy clusters measure • Matter content Wm (from baryon fraction) • Intermediate scale fluctuation amplitude (XLF) • Cosmic microwave background (CMB) -> • Fluctuation amplitude on large scales • Neutrinos = fast moving dark matter (HDM) • Massive neutrinos would smear out collapsing structures on intermediate to small scales

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