cosmic structures: challenges for astro-statistics ofer lahav department of physics and astronomy...
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Cosmic Structures:Challenges for Astro-Statistics
Ofer Lahav Department of Physics and Astronomy University College London
* Data compression – e.g. P(k) * Features in P(k) * Parameter estimation and model selection* Beyond the 2-point statistic* The big questions: dark matter, dark energy, galaxy formation
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FF
2MASS Galactic chart 2MASS Galactic chart (Tom Jarrett)(Tom Jarrett)
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Redshift Surveys
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The Cosmic Web
CfA Great Wall
SDSS
Great Attractor 2dFGRS
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Is the universe a fractal?A short answer: NO
N(<R) / RD
D=1.2
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clumpiness
Small scales
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Correlation Function per Type
Why a power law?
different slopes for blue and red explained by different halo Occupation numbers
dP / n [1+(r)] dV
r) = (r/r0)-
Madgwick et al. 03
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Halo model for LSS
Picture credit: Cooray & Sheth (2002)
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The halo model – the ‘new biasing’
Collister & Lahav, astro-ph/0412516
Truncated NFW fit with C=2.4§ 0.2 using 2dF Groups
P(k) = Plin+Phalo
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Neutrinos decoupled when they were still relativistic,hence they wiped out structure on small scales
112 neutrinos per cm3
WDMCDM+HDM
CDM
From 2dF < 0.04 ; M < 1.8 eV (Elgaroy & OL 2003)From Ly-a+SDSS +CMB M < 0.17 eV (Seljak et al. 2006)
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Mock Universes:Models vs. Epoch
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Same amplitudes, different phases
Chiang & Coles 2000
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Non-Gaussianity in LSS
Guassian density contrast pdf will turn into (roughly) a log-normal pdf.
Gravity is an amplifier: the rich gets richer
the poor gets poorer
• Needed: non-G tests, shape finders
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CiC
2dF early type
Wild et al 2004
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Minkowski functionals
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( )2
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Martinez et al.
Wavelet MF V3 applied to 2dF
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Are the 2dFGRS superclustersanomalous?
Baugh et al., Erdogdu et al., Murphy & OL
Abell Abell clustersclusters77 groups 77 groups (>8)(>8)
Abell Abell clustersclustersgroups groups (>8)(>8)
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MegaZ-LRG *Training on ~13,000 2SLAQ*Generating with ANNz Photo-z for ~1,000,000 LR over 5,000 sq deg
z = 0.046
Collister, Lahav, Blake et al.
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power spectra out to 1 Gpcvary 4 parameters
Non-linear P(k)
Linear P(k)
Minimum fitted
multipole
Blake et al., astro-ph/0605303
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Baryon Wiggles as Standard Ruler
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The Dark Energy Survey
• 4 complementary techniques:
* Cluster counts & clustering * Weak lensing * Galaxy angular clustering * SNe Ia distances
Build new 3 deg2 camera on the CTIO Blanco 4m Construction 2005-2009 Survey 2009-2014 (~525 nights)
5000 deg2 g, r, i, z 300, 000, 000 galaxies with photo-z
Science goal: w to ~5-10% on each technique
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LSS - The Steps Ahead
* Spetcroscopic and photometric Surveys
Of 106 – 108 galaxies
* Beyond the 2-point statistic:
higher meoments, MF, shape finders, phases…
* The interplay with galaxy formation
* Dark energy surveys (BAO, WL)
* The VO infra-structure