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