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
FF
2MASS Galactic chart 2MASS Galactic chart (Tom Jarrett)(Tom Jarrett)
Redshift Surveys
The Cosmic Web
CfA Great Wall
SDSS
Great Attractor 2dFGRS
Is the universe a fractal?A short answer: NO
N(<R) / RD
D=1.2
clumpiness
Small scales
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
Halo model for LSS
Picture credit: Cooray & Sheth (2002)
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
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)
Mock Universes:Models vs. Epoch
Same amplitudes, different phases
Chiang & Coles 2000
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
CiC
2dF early type
Wild et al 2004
Minkowski functionals
( )2
Martinez et al.
Wavelet MF V3 applied to 2dF
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)
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.
power spectra out to 1 Gpcvary 4 parameters
Non-linear P(k)
Linear P(k)
Minimum fitted
multipole
Blake et al., astro-ph/0605303
Baryon Wiggles as Standard Ruler
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
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