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Upper limits on neutrino masses from cosmology: new results

Upper limits on neutrino masses from cosmology: new results. Øystein Elgarøy (Institute of theoretical astrophysics, University of Oslo) Collaborator: Ofer Lahav (UCL, London) SNOW06. Room for neutrinos?. NASA/WMAP Science Team. Absolute Masses of Neutrinos. E & Lahav, NJP 05.

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Upper limits on neutrino masses from cosmology: new results

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  1. Upper limits on neutrino masses from cosmology: new results Øystein Elgarøy (Institute of theoretical astrophysics, University of Oslo) Collaborator: Ofer Lahav (UCL, London) SNOW06

  2. Room for neutrinos? NASA/WMAP Science Team

  3. Absolute Masses of Neutrinos E & Lahav, NJP 05

  4. What do we mean by ‘systematic uncertainties’? • Cosmological (parameters and priors) • Astrophysical (e.g. Galaxy biasing) • Instrumental (e.g. ‘seeing’)

  5. Neutrinos decoupled when they were still relativistic, hence they wiped out structure on small scales k > knr = 0.026 (m /1 eV)1/2m1/2 h/Mpc Colombi, Dodelson, & Widrow 1995 CDM CDM+HDM WDM Massive neutrinos mimic a smaller source term

  6. P(k)=A kn T2(k) Neutrino Free Streaming DP(k)/P(k) = -8 Wn /Wm (Hu et al. 1998)

  7. Neutrino mass from Cosmology All upper limits 95% CL, but different assumed priors !

  8. Example of “model” systematics: Dark energy • Most cosmological neutrino mass limits have assumed that the dark energy is a cosmological constant • There are (too!) many alternatives • Common parameterization: p = w where w is a constant (can be < -1)

  9. Hannestad, PRL95 (2005) 221301

  10. Why this degeneracy? • P(k) sensitive to the combination fm • But mh2 eV • If one allows for w <-1, SNIa data allow large values of m • The degeneracy is indirect, the effect of varying w on P(k) corresponds roughly to varying the amplitude

  11. Modified gravity TeVeS vs LCDM (D. F. Mota et al., in preparation)

  12. Primordial power spectrum

  13. The 2dF Galaxy Redshift Survey • APM selected • Magnitude bJ < 19.45 • Median z  0.1 • 230 K measured • All public • Cosmology • Galaxy properties

  14. The 2dFGRS Team Members I.J. Baldry, C.M. Baugh, J. Bland-Hawthorn, T.J. Bridges, R.D. Cannon, S. Cole, C.A. Collins, M. Colless (PI),W.J. Couch, N.G.J. Cross, G.B. Dalton, R. DePropris, S.P. Driver, G. Efstathiou, R.S. Ellis, C.S. Frenk, K. Glazebrook, E. Hawkins, C.A. Jackson, O. Lahav, I.J. Lewis, S.L. Lumsden, S. Maddox (PI), D.S. Madgwick, S. Moody, P. Norberg, J.A. Peacock (PI), B.A. Peterson, W. Sutherland, K. Taylor http://www.mso.anu.edu.au/2dFGRS/

  15. The 2dFGRS Power Spectrum l=200 l=1500 • 160 K (Percival et al.) • Redshift space • Convolved • Good fit to CDM • Wiggles ? 50 Mpc/h 7 Mpc/h

  16. Empirical test of bias • Red galaxies are more common in the centres of rich clusters than blue galaxies • The opposite is the case in the rest of the universe • Can get a feeling of the significance of bias for m limits by splitting the 2dF sample into red and blue galaxies

  17. From Cole et al. 2005

  18. Preliminary results • Fix mh=0.18, fb=0.17, n=1 • Vary f, marginalize over amplitude and non-linear correction parameter Q (see Cole 2005) • Look at various cuts in k • Gives an idea of the importance of bias

  19. ØE,OL,Percival, Cole & Peacock (in preparation)

  20. ØE, OL, Percival, Cole & Peacock (in preparation)

  21. Summary • Cosmological neutrino mass limits start to probe the sub-eV range • Need to focus on systematics • No data set can do the job alone • Dark energy: degeneracy with w understood and can be dealt with, but not much has been done on “weird” models • Bias: red and blue galaxies cluster differently, is it taken properly into account?

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