Massive Neutrinos and Cosmology

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Massive Neutrinos and Cosmology
n-2004, Paris

• Brief history of Hot Dark Matter
• Limits on the total Neutrino mass from
• redshift surveys Mn lt 0.7-1.8 eV
• The CMB alone is not sensitive to Mn.
• Mixed Dark Matter?

Ofer Lahav University College London
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SDSS Galaxy images and Redshifts
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Brief History of Hot Dark Matter

• 1970s Top-down scenario with massive
  neutrinos (HDM)
• Zeldovich Pancakes
• 1980s HDM - Problems with structure formation
• 1990s Mixed CDM (80) HDM (20 )
• 2000s Baryons (4) CDM (26) Lambda (70)
  
• room for HDM?

e.g. Primack, astro-ph/0112336
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The model 95 of cosmologists favour today
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The Cosmic Budget (Post-WMAP)
Reality or Epicycles? More components? -
e.g. neutrinos?
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Density Fluctuations vs. Scale

Tegmark
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Precision Cosmology? Not Just Yet
Bridle, OL, Ostriker Steinhardt 2003 OL
Liddle 2003
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The 2dF Galaxy Redshift Survey

• APM selected
• Magnitude bJ lt 19.45
• Median z ? 0.1
• 230 K measured
• All public
• Cosmology
• Galaxy properties

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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/ On
2dF Sociology see OL, astro-ph/0105351
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The 2dF Redshift Machine

• 400 fibres in 2 deg Field

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The 2dFGRS Power Spectrum
l200
l1500

• 160 K (Percival et al.)
• Redshift space
• Convolved
• Good fit to LD CDM
• Wiggles ?

50 Mpc/h
7 Mpc/h
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2dF vs SDSS
50 Mpc/h

Pope et al. 2004
Tegmark et al. 2003
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Neutrino properties

• The number of neutrino species Nn affects
• the expansion rate of the universe, hence BBN.
• BBN constraints Nn between 1.7 and 3 (95 CL)
• (e.g. Barger et al. 2003).
• We shall assume Nn 3 and no annihilation
• (cf. Beacom et al. 2004)
• Wn h2 Mn/(94 eV)

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P(k)A kn T2(k)

Neutrino Free Streaming DP(k)/P(k) -8 Wn /Wm
(Hu et al. 1998)
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Weighing Neutrinos with 2dFGRS

• Free streaming effect
• Wn/Wm lt 0.13
• Total n mass Mlt 1.8 eV
• 0.001 lt Wn lt 0.04
• (Oscillations) (2dF)
• a Four-Component Universe ?

Wn 0.05
0.01
0.00
Elgaroy , Lahav 2dFGRS team, astro-ph/0204152
, PRL
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Absolute Masses of Neutrinos

• Based on
• measured
• squared mass
• differences
• from solar and
• atmospheric
• oscillations
• Assuming
• m1 lt m2 lt m3

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2dF limits on the neutrino mass
n 0.9
n1.0
Prior 0lt Wmlt0.5
n 1.1
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Galaxy biasing
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Galaxy Biasing
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To b or not to b ?
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Biasing from halo occupation redshift
distortion models


Total neutrino mass
Seljak 2001
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Biasing vs. neutrino mass
Pg(k) b2(k) Pm(k) b(k) a log(k) c
a
---- SAM for Lgt0.75 L
Total neutrino mass
Elgaroy Lahav astro-ph/030389
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The History of CMB observations
1965
Discovery
COBE
1992
2003
WMAP
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WMAP Results
T-T power spectrum
Polarisation T-E power spectrum

Bennett et al. 2003
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Neutrinos and the CMB

• The CMB alone in NOT sensitive to massive
• neutrinos.
• The WMAP result (Spergel at al. 2003) of
• Mn lt 0.69 eV (95 CL) is based on
• WMAP2dFLy-a
• 2dF is sensitive to Wn/Wm
• WMAP constrains Wm (and other parameters)

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X-ray galaxy clusters CMB
Allen, Schmidt Bridle (2003) Claimed a
preferred value Mn 0.56 0.30-0.26 eV
The idea Connecting small and large
scales (Fukugita et al. 2000)
But it depends on the M-Lx relation for
clusters. This really illustrates the
degeneracy between the amplitude of fluctuations
and the neutrino mass.
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Mixed Dark Matter?
WMAP

• Wm1, Wn0.2, h0.45
• Consistent with 2dF.
• To fit WMAP,
• a break is required in the
• Primordial power-spectrum
• (e.g. Blanchard et al. 2003).
• Also at odds with HSTs H0,
• SNIa , cluster evolution and
• baryon fraction.
• Elgaroy Lahav, JCAP 2003
• Astro-ph/030389

P(k) 2dF
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Neutrino mass from Cosmology

Data Authors Mn S mi
2dFGRS Elgaroy et al. 02 lt 1.8 eV
WMAP2dF Spergel et al. 03 lt 0.7 eV
WMAP2dF Hannestad 03 lt 1.0 eV
SDSSWMAP Tegmark et al. 04 lt 1.7 eV
WMAP2dF SDSS Crotty et al. 04 lt 1.0 eV
Clusters WMAP Allen et al. 04 0.560.30-0.26 eV
All upper limits 95 CL, but different assumed
priors !
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Summary

• Redshift surveys (supplemented by the CMB)
• constrain Mn lt 0.7-1.8 eV
• within the L-CDM scenarios, subject to
• priors.
• Alternatives - MDM?
• Future errors down to 0.1 eV
• using SDSSPlanck,
• and weak gravitational lensing of background
  galaxies and of the CMB.