Neutrino Mass & the Lyman-α Forest. Kevork Abazajian University of Maryland

Transcription

1 Neutrino Mass & the Lyman-α Forest Kevork Abazajian University of Maryland INT Workshop: The Future of Neutrino Mass Measurements February 9, 2010

2 Dynamics: the cosmological density perturbation spectrum Power spectrum of cosmological density fluctuations P (k) = δ k 2 Primordial Harrison-Zeldovich: from scale invariance P (k) k Natural solution to perturbation spectrum: self-similar evolution Predicted by inflation P (k) k n n 1 P(k) k

3 The Cosmological Matter Power Spectrum? Perturbations enter horizon: Matter Domination [δφ mat const] Radiation Domination [δφ rad decays] P(k) horizon size k

4 How does probe neutrinos? (Assuming thermal equilibrium) ρ ν = m i n νi Matter Domination Radiation Domination Ω ν mνi 93 h 2 ev P(k) E 2 = p 2 + m 2 Is this a coincidence? k

5 Distinguishing Features in the Power Spectrum Σm νi =0.14 ev P(k) Galaxy Surveys Σm νi =1.4 ev k Relative Lesgourgues Amplitude:CMB+Lya & Pastor (2006) 1. Shape Information: Galaxy Surveys (Future: Weak Lensing Surveys) 2. Relative Amplitude Information: CMB plus Lyman-alpha Forest, Galaxy Bias P(k) P(k) = 12 Ω ν Ω m

6 Relative Large Scale Amplitude: PLANCK (Martin White)

7 Forecast Precision Cosmology: PLANCK (Martin White)

8 P(k) k The Primordial Spectrum: Precision Determination at Large Scales P (k) =Ak n WMAP 5 + BAO + SN: (Komatsu et al. 2008) A = ± (3.4%) n = 0.96 ± (1.4%) PLANCK + SDSS LRG: (Eisenstein, Hu, Tegmark 1998) A = ± (0.35%) n = ± (0.8%) forecast!

9 Measuring P(k) CMB SDSS Ly-α SDSS w(p)

10 Ωm Degeneracy Ω m

11 The Onset of Nonlinearity at Small Scales

12 The Lyman-alpha Forest (Croft et al 1999)

13 Example Lyman-alpha Forest Flux Spectrum the flux power spectrum measured here λ (Å) 13

14 The SDSS Ly-α Flux Power Spectrum Measurement Simply a 1D power spectrum of the flux in relevant bins However, power is measured simultaneously in the: the transmitted flux/absorption intrinsic quasar spectrum variation sky, continuum quasar, and count noise S/N ~ 3 Leads to a need to accurately disentangle sources of power and noise in the measurement

15 Lyman-alpha Forest Constraints on mν Only public set: McDonald et al. (2006) SDSS PF(k) Measurement

16 WMAP+ACBAR+CBI + SDSS + HST: ν mass limits WMAP+SDSS P g (k) WMAPext+SDSS P g (k) + HST H 0 + SDSS Ly-α Preliminary

17 Summary of Cosmological Neutrino Mass Constraints WMAP1 WMAP7 2dFGRS Shape (conservative but very important limits on ) [Elgaroy et al 2002]: SDSS 3D Pg(k) shape + WMAP I [Tegmark et al, 2003]: CMB + SDSS 2-point correlation function (nonlinear modeling): [Abazajian et al 2005]: WMAP 7 alone [Komatsu et al 2010]: Σm νi Σm νi Σm νi Σm νi SDSS Ly-alpha forest + WMAP 3-year [Seljak et al., 2006]: Σm νi 1.8 ev 1.8 ev 0.69 ev < 1.3 ev 0.17 ev WMAP 7 + SDSS LRG BAO + H0 [Komatsu et al, 2010]: Ω m 95% CL... Σm νi < 0.58 ev

18 SDSS+WMAP3 Lyman-alpha Constraints (Seljak et al 2006) WMAP3: σ 8 = P(k) WMAP Ly-a SDSS Ly-alpha (Seljak et al 2003): σ 8 = k Ly-alpha N ν = Seljak et al. Lyα WMAP3 N ν = BBN, Cyburt et al N ν = 3.04 (standard model)

19 Problems in Temperature Requirements of the IGM? (CDM & WDM analysis) Very high T0 Viel & Haehnelt (2005); Viel et al 2006 ~35000 K

20 Abazajian, Lidz, Ricotti, in prep.

21 The SDSS Ly-α Flux Power Spectrum Measurement Simply a 1D power spectrum of the flux in relevant bins However, power is measured simultaneously in the: the transmitted flux/absorption intrinsic quasar spectrum variation sky, continuum quasar, and count noise S/N ~ 3 Leads to a need to accurately disentangle sources of power and noise in the measurement

22 SDSS Lyα Flux Power & Noise There exists a positive correlation between an increase in spectral noise and increased primordial power Noticed in McDonald et al 2005 Abazajian et al in prep.

23 SDSS Lyα Flux Power & Noise McDonald et al 2005 noticed, but was it properly corrected? - split of data into high-noise and low noise halves - found same P(k) at zero noise for both splits - did linear fit to all data

24 SDSS Lyα Flux Power & Noise Corrected in our analysis via removal of highest noise bins to a point where the linear fit is statistically sound

25 Done for each k at each z

26 Noise-Bias Quantification Dependence Amplitude shift, larger errors: mν, σ8? and implications for CDM / WDM? Abazajian et al in prep.

27 Summary of Cosmological Neutrino Mass Constraints WMAP1 WMAP7 2dFGRS Shape (conservative but very important limits on ) [Elgaroy et al 2002]: SDSS 3D Pg(k) shape + WMAP I [Tegmark et al, 2003]: CMB + SDSS 2-point correlation function (nonlinear modeling): [Abazajian et al 2005]: WMAP 7 alone [Komatsu et al 2010]: Σm νi Σm νi Σm νi Σm νi SDSS Ly-alpha forest + WMAP 3-year [Seljak et al., 2006]: Σm νi 1.8 ev 1.8 ev 0.69 ev < 1.3 ev 0.17 ev SDSS LRG BAO + H0 + WMAP 7 [Komatsu et al, 2010]: Ω m 95% CL... Σm νi < 0.58 ev

28 Estimating Upcoming Cosmological Neutrino Mass Constraints P P 1% 12 Ω ν Ω m Hu, Eisenstein & Tegmark 1998; Abazajian & Dodelson 2003 Ω ν mνi 93 h 2 ev = m ν (1%/12) Ω m (93h 2 ev) = m ν 0.01 ev Kaplinghat et al PRL 2003 (CMB WL) Wang et al PRL 2005 (WL Clusters) De Bernardis et al (Opt. WL)

29 Summary The Lyman-alpha forest is a sensitive probe of gas and dark matter clustering at small scales. However, the Lyman-alpha forest may not be as robust as a precision cosmology tool as originally proposed. Degeneracies in the gas temperature-density relation, allowed conservatively to vary, lower sensitivities. The SDSS Lyman-α forest flux power spectrum is has strong noise correlations with power that must be corrected appropriately, modifying the amplitude of power. An independent analysis is forthcoming.