9,000,000,000 Years of Gravity at Work in the Cosmic Factory

9,000,000,000 Years of Gravity at Work in the Cosmic Factory

Centre de Physique ThéoriqueUniversité de Provence

Christian Marinoni

Nice 25-27 Jan 2005

• Galaxy bias - Biasing from a theoretical & observational perspective • The survey of the LSS at high z - Results : biasing properties up to z=1.5

• Cosmological implication of our results - Test of the Gravitational Instability Paradigm (GIP)

Outline

Marinoni et al. 2005 A&A in press (astro-ph/0506561)

Theoretical Background:Theoretical Background:

t

Dynamics of matter fluctuations

So what’s the problem? So what’s the problem? Formation and evolution of luminous matterFormation and evolution of luminous matter

Dynamics of galaxy fluctuations

• Where and when did galaxies form?

• How do they evolve?

• Formal problem:

g g ()

g

Biasing scheme

From an observational point of view....From an observational point of view....

• Biasing must exist on both small and large cosmological scales! - Halo and galaxy profiles - Galaxies of different types cluster differently - Void phenomenon

From an observational point of view....From an observational point of view....

• Biasing must exist on both small and large cosmological scales! - Halo and galaxy profiles - Galaxies of different types cluster differently - Void phenomenon

• Biasing relation depends in principle on some “hidden” variable ...

g=g(, A1, A2, A3 ... t) Stochasticity in the plane g

From an observational point of view....From an observational point of view....

• Up to now most measurement methods constrain i.e. measure only linear bias (scalar parameter)

g b

• Biasing must exist on both small and large cosmological scales! - Halo and galaxy profiles - Galaxies of different types cluster differently - Void phenomenon

• Biasing relation depends in principle on some “hidden” variable ...

g=g(, A1, A2, A3 ... t) Stochasticity in the plane g

Where do we stand with observationsWhere do we stand with observations

No bias locally. At present time ligh follows matter

Where do we stand with observationsWhere do we stand with observations

At high z , blue galaxies more correlated than matter

Where do we stand with observationsWhere do we stand with observations

Extremely red objects at z~1 more clustered w/r to blue

Where do we stand with observationsWhere do we stand with observations

Where do we stand with observationsWhere do we stand with observations

Conflicting evidences about biasing evolution!

• Galaxy bias - Biasing from a theoretical & observational perspective • The survey of the LSS at high z - Results : biasing properties up to z=1.5

• Cosmological implication of our results - Test of the Gravitational Instability Paradigm (GIP)

Outline

The : Vimos-VLT Redshift SurveyThe : Vimos-VLT Redshift Survey

French-Italian teamFrench-Italian team : P.I. Olivier LeFèvre

– Laboratoire d ’Astrophysique (Marseille): Adami, Arnouts, Foucaud, Ilbert, Le Brun, Mazure, Meneux, Paltani, Tresse

– OABo, IRA-CNR (Bologna): Bardelli, Bondi, Bongiorno, Cappi, Ciliegi, Marano, Pozzetti,Scaramella (Rome), Vettolani, Zamorani, Zanichelli, Zucca

– IASF, OABr (Milan): Bottini, Cucciati, Franzetti, Garilli, Guzzo, Iovino, Maccagni, Marinoni, Pollo, Scodeggio

– IAP (Paris): Charlot (MPA), Colombi, McCracken, Mellier

– OAC (Naples): Arnaboldi, Busarello,Radovich– OMP (Toulouse): Contini, Mathez, Pello, Picat,

Lamareille

Imaging Survey (CFHT, ESO-MPI 2.2, ESO-NTT)

16 sq.deg in 4 fields 22 deg L~100h-1 Mpc at z~1

(U)BVRI(K) filters, ~3x10 objects

The in a nutshell

2

6

McCracken et al 2004, Radovich et al. 2004, Iovino 2005McCracken et al 2004, Radovich et al. 2004, Iovino 2005

Public data release on http://cencosw.oamp.fr

LeFèvre et al 2004 AA in press (astroph/0409133)LeFèvre et al 2004 AA in press (astroph/0409133)Spectroscopic Survey (Vimos at VLT):

Purely flux -limited survey, No preselections

16 deg down to I=22.5, z<1.3, 36000 observed

1 deg down to I=24,z<2, 13000 observed

Sample: Deep Sample: Deep “cone” “cone” (2h Field: first-epoch data)(2h Field: first-epoch data)

• ~7000 galaxies with secure redshifts, IAB24

• Coverage:0.7x0.7 sq. deg (40x40 Mpc at z=1.5)

• Volume sampled:2x106 Mpc3 (~CfA2) (1/16th of final goal)

4300 Mpc

•Mean inter-galaxy separation at z=0.8 <l>~4.3 Mpc (~2dF at z=0.1)

•Sampling rate: 1 over 3 galaxies down to I=24

z=0

z=1.5

2DFGRS/SDSS stop here

The Density Field (smoothing R=2Mpc)

The Probability Distribution Function (PDF) of galaxy overdensities

Probability of having a density fluctuation in the range (,+d) within a sphere of radius R randomly located

in the survey volume

fR()

Low density

High density

The 1P-PDF of galaxy overdensities g (The 1P-PDF of galaxy overdensities g ())

• The PDF is different at different cosmic epochs

R

Z=0.7-1.1

Z=1.1-1.5

• Systematic shift of the peak towards low density regions as a function of cosmic time

• Cosmic space becomes dominated by low density regions at recent epochs

Volume limited sample M<-20+5log h

Time Evolution of the galaxy PDF

A possible InterpretationA possible Interpretation

Gravitational instability in an expanding universe ???

v (r)

r2 dV

The PDF of mass overdensities f(The PDF of mass overdensities f(): Shape): Shape

Z=0.7-1.1 Z=1.1-1.5 Conclusion:Galaxies are Spatially distributed in a different way (biased) with respect to dark matter at high z

Lognormal!(Coles & Jones 1991)

g(g )dg ()d

Bias: difference in distribution of DM and galaxy fluctuations

Measuring the galaxy bias up to z=1.5 with the VVDS

Linear Bias Scheme:

g b (Kaiser 1984)

Our goal:

g b(z,,R)• Redshift evolution• Non linearity• Scale dependence

Strategy

Derive the biasing function

Sigad et al 2000Marinoni & Hudson 2002Ostriker et al. 2003

g g ()

The PDF of galaxy overdensities gThe PDF of galaxy overdensities g ((): Shape): Shape

)( gg

Z=0.7-1.1 Z=1.1-1.5

The biasing function: Time evolutionThe biasing function: Time evolution

• Scale independent on 5 < R(Mpc) < 10

(Norberg et al. 04)

2dF • Galaxies were progressively more biased mass tracers in the past

• Evolution: weak for z < 0.8

stronger for z > 0.8

15 Mpc Smoothing

• Non linearity at a level <10% on scales 5<R<10 Mpc (Local slope is steeper (bias stronger) in underdense regions)

The biasing function: 2) Shape b()L

• Also at high z, galaxy bias depends on luminosity: More luminous galaxies are more spatially segregated with respect to DM

• Luminous galaxies do not form in underdense regions

The biasing function: 2) Shape b()

z

• At present epochs galaxies form also in low density regions, while at high z the formation process is inhibited in

underdensities

The Problem: Formation and Evolution of luminous matterThe Problem: Formation and Evolution of luminous matter

Dynamics of galaxy fluctuations

• Where do galaxies form? In the high density peaks of the dark matter distribution

• How do they evolve: As time goes by they start forming also in low density regions

Theoretical Interpretation: Which is the physical mechanism governing biasing evolution?

Gravity(Dekel and Rees `88Tegmark & Peebles `98)

Merging(Mo & White `96Matarrese et al `97)

IstantaneousStar Formation(Blanton et al `02)

• Cosmological bias (definition) - Biasing from a theoretical perspective - Biasing from an observational point of view

• The VVDS survey of the LSS at high z - A new method to measure biasing - Results : biasing properties up to z=1.5

• Cosmological implication of our results - Test of the Gravitational Instability Paradigm

Outline

Test of the Gravitational Instability Paradigm

~ costant with z

decrease with z

Volume limited sample M<-20+5log h

Test of the Gravitational Instability Paradigm

)0()()()( zDzbz Lg

S3g (z)b1

1(z) S3 3b2

b1

S3 34 /7 (n 3)

Peebles 1980

Juskiewicz et al. 1993

ConclusionsConclusions

• Determination of the PDF of galaxy fluctuations from a complete Volume-limited redshift survey covering the range 0.5< z <1.5 (large connected sky regions, all the galactic populations).

• Low order moments of the galaxy PDF evolve as predicted by the linear and second order perturbation theory. GIP predictions consistent over 9,000,000,000 years

• The bias function is complex! First time detection of non linearity on large scales (10% effect).

• Significant evolution of the `linearized’ bias 0.7<z<1.5.

• No single simple physical model is able to describe the observed evolution.

Reconstruction Completeness

Is the lognormal PDF of mass a good approximation of reality?Is the lognormal PDF of mass a good approximation of reality?

CDM Hubble Volume simulation (Virgo cons.)

Test of the Gravitational Instability Paradigm : Motivation

The Origin of the Large Scale Structure is one of the key issue in Cosmology.A plausible assumption is that structures grow via gravitational collapse of density fluctuations that are small at early times, but is vital to test this hypothesis.

J.A.Peacock, Nature 2002

Is gravity the engine of the cosmic factory?

Growth of Cosmic StructuresGrowth of Cosmic Structures

Continuity eq. + Poisson eq. + Poisson eq.

Initial Condition: Primordial Power Spectrum

daaa

at 3)0()(

nk kttkP )0()0,( 2

(r, t)R (t)(t)

SNIa+Wmap measurements

a(t,)

n 1Friedmann eq.

Harrison Zel’dovich.

The Evolution of the LSS in linear approximation......

Fundamental variable for LSS studies:The Matter Fluctuation Field

Assume knowledge of cosmological background

r

-1

• Top-Hat smoothing on various scales R (5-15 Mpc)

• Correction for radial selection function of the sample

• Correction for the VVDS sampling rate

• Shot noise minimization (Wiener-filter in Fourier space)

Reconstruction of the Galaxy Density Field

The PDF of mass: The PDF of mass: (())

Problem: we measure galaxies in redshift space!

Real Space Model Cole 1992

z(R,z)

(y)1

2 2

1

yExp{

[ln y 2 /2]2

2 2 }

y 1

2 ln[1 r(R,z)2]

z(z) r (0)D(z)[12

3f (z)

1

5f (z)2]

Kaiser 87