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

F 2MASS Galactic chart (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) / R D 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/r 0 ) -  Madgwick et al. 03

Halo model for LSS Picture credit: Cooray & Sheth (2002)

The halo model – the ‘new biasing’ Collister & Lahav, astro-ph/ Truncated NFW fit with C=2.4 § 0.2 using 2dF Groups P(k) = P lin +P halo

Neutrinos decoupled when they were still relativistic, hence they wiped out structure on small scales 112 neutrinos per cm 3  WDMCDM+HDMCDM 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 superclusters anomalous? Baugh et al., Erdogdu et al., Murphy & OL  Abell clusters 77 groups (>8)  Abell clusters  groups (>8)

MegaZ-LRG *Training on ~13,000 2SLAQ *Generating with ANNz Photo-z for ~1,000,000 LR over 5,000 sq deg  z = Collister, Lahav, Blake et al.

power spectra out to 1 Gpc vary 4 parameters Non-linear P(k) Linear P(k) Minimum fitted multipole Blake et al., astro-ph/

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 deg 2 camera on the CTIO Blanco 4m Construction Survey (~525 nights) 5000 deg 2 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 10 6 – 10 8 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