1. 9,000,000,000 Years of Gravity at Work in the Cosmic Factory Christian Marinoni Centre de Physique Théorique, University of Provence And the team

2. The survey of the Large Scale Structure of the Universe at high z Galaxy bias (definition) - Biasing from a theoretical perspective - Biasing from an observational point of view - VVDS Results : biasing properties up to z=1.5 Cosmological implication of our results (test of the Gravitational Instability Paradigm) Outline Marinoni et al. 2005 A&A in press (astro-ph/0506561)

4. The : Vimos-VLT Redshift Survey French-Italian team French-Italian team : P.I. Olivier LeFèvre (LAM Marseille) –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, Pollo, Scodeggio –IAP (Paris): Charlot (MPA), Colombi, McCracken, Mellier –OAC (Naples): Arnaboldi, Busarello,Radovich –OMP (Toulouse): Contini, Mathez, Pello, Picat, Lamareille

5. Imaging Survey (CFHT, ESO-MPI 2.2, ESO-NTT)  16 sq.deg in 4 fields 2  2 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 2005 McCracken 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) AB 2 2 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

6. Sample: Deep “cone” (2h Field: first-epoch data) ~7000 galaxies with secure redshifts, I AB  24 Coverage: 0.7x0.7 sq. deg (40x40 Mpc at z=1.5) Volume sampled: 2x10 6 Mpc 3 (~CfA2) (1/16th of final goal) 4300 Mpc Mean inter-galaxy separation at z=0.8 ~4.3 Mpc (~2dF at z=0.1) Sampling rate: 1 over 3 galaxies down to I=24 z=0 z=1.5

7. The Density Field (smoothing R=2Mpc) 2DFGRS/SDSS stop here

8. Density field Galaxies z=0.9 z=1 z=0.9

9. Filaments

10. Walls

11. The survey of the LSS at high z Galaxy bias (definition) - Biasing from a theoretical perspective - Biasing from an observational point of view - VVDS Results : biasing properties up to z=1.5 Cosmological implication of our results (test of the Gravitational Instability Paradigm) Outline Marinoni et al. 2005 A&A in press (astro-ph/0506561)

12. Theoretical Background: Continuity eq. + Poisson eq. + Poisson eq. Initial Condition: Primordial Power Spectrum SNIa+Wmap measurements Friedmann eq. Harrison Zel’dovich. The Evolution of the LSS in linear approximation...... Fundamental variable for LSS studies: The Matter Fluctuation Field......is a solved problem! r  

13. Theoretical Background: (Fully non linear approach) t

14. So what’s the problem? Formation and evolution of luminous matter Dynamics of galaxy fluctuations Where and when did galaxies form? How do they evolve? Formal problem: Biasing scheme

15. 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

16. 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 ( , A 1, A 2, A 3... t) Stochasticity in the plane  g 

17. From an observational point of view.... Up to now most measurement methods constrain i.e. measure only linear bias (scalar parameter) 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 ( , A 1, A 2, A 3... t) Stochasticity in the plane  g 

18. Where do we stand with observations No bias locally. At present time ligh follows matter

19. Where do we stand with observations At high z “galaxies” more correlated than matter

20. Where do we stand with observations Red objects more spatially clustered w/r to blue

21. Where do we stand with observations

22. Conflicting evidences about biasing evolution!

23. Bias: difference in distribution of DM and galaxy fluctuations  Measuring the galaxy bias up to z=1.5 with the VVDS Marinoni et al. 2005 A&A in press astro-ph/0506561 Linear Bias Scheme:(Kaiser 1984) Our goal: Redshift evolution Non linearity Scale dependence Strategy  Derive the biasing function Marinoni & Hudson 2002 Ostriker et al. 2003

24. 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()fR()  Low density High density

25. The PDF of galaxy overdensities g (  ): Shape 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

26. The PDF of mass overdensities f (  ): Shape R Conclusion: Galaxies are Spatially distributed in a different way (biased) with respect to dark matter at high z Z=0.7-1.1 Z=1.1-1.5

27. The biasing function: 1) 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 Cosmic Variance

28. Theoretical Interpretation 1: Galaxies are biased at birth Kaiser model

29. The 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

30. Theoretical Interpretation 2: Which is the physical mechanism driving the evolution of biasing? Gravity (Dekel and Rees ’88) Merging (Mo & White ’98) Istantaneous Star Formation (Blanton et al ’02)

31. The survey of the LSS at high z Galaxy bias (definition) - Biasing from a theoretical perspective - Biasing from an observational point of view - VVDS Results: biasing properties up to z=1.5 Cosmological implication of our results (test of the Gravitational Instability Paradigm) Outline Marinoni et al. 2005 A&A in press (astro-ph/0506561)

32. Test of the Gravitational Instability Paradigm The origin of the Large Scale Structure is one of the key issue in cosmology. A pausible 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?

33. Continuity eq. Motion eq. Poisson eq. Linear approach Test of the Gravitational Instability Paradigm Compare to observations bias Compute low order moments of the galaxy PDF - variance and skewness

34. constant 0.7<z<1.5 Test of the Gravitational Instability Paradigm decreasing 0.7<z<1.5

35. constant 0.7<z<1.5 Test of the Gravitational Instability Paradigm decreasing 0.7<z<1.5 8

36. Test of the Gravitational Instability Paradigm Peebles 1980 Juskiewicz et al. 1992

37. Conclusions Determination of the PDF of galaxy fluctuations from a complete flux-limited redshift survey covering the range 0.5< z <1.5 (large connected sky regions, all the galactic populations). Confirms Kaiser scheme: Galaxies are biased at birth. Galaxies form in the highest peaks of dark matter distribution. The bias function is complex! detection of non linearity on large scales (10% effect). Significant evolution of bias 0.7<z<1.5. No single simple physical model is able to interpret the observed evolution. Gravity sets the stage for galaxy formation

38. Conclusions Once: it was the ‘old’ Cosmological Constant Ex: Velocity field Now: cosmological parameters are fixed, therefore the biasing schemes tells us about the physics of formation and evolution of the Large Scale Structures in the universe

39. Conclusions Gravity is the engine driving structure evolution in the Universe - Stochastic, fractals (Pietronero et al.) - Cosmic explosions (Ostriker & Cowie) - Phase transitions (Brandeberger et al., Amendola et al). Gravity amplifies primordial matter fluctuations into the observed LSS. Low order moments of the galaxy PDF on large scales evolve as predicted by the linear and second order perturbation theory of the gravitational instability paradigm. Predictions of Gravitational Instability Paradigm tested over the past 9 billions year

40. The PDF of mass:  (  ) Problem: we measure galaxies in redshift space! Real Space Model Cole 1992 Kaiser 87

41. Reconstruction Completeness

42. Is the lognormal PDF of mass a good approximation of reality?  CDM Hubble Volume simulation (Virgo cons.)

43. 4) How old is the first virialized structure which formed in the Universe?

44. 4) How old is the first virialized structure which formed in the Universe?

45. 4) How old is the first virialized structure which formed in the Universe? LCDM SCDM

47. What do we want to know: What are the structures in the early Universe? Are they similar to what we observe today? What are the properties of the most relevant statistics describing the distribution of galaxy fluctuations in the high z universe? Study of the shape and evolution of the PDF of galaxy fluctuations Is the PDF of galaxy fluctuations equal to the PDF of matter fluctuations at every cosmic epoch? Is biasing really linear? Does it evolve with cosmic time?

48. Galaxy bias depends on redshift: it encreases as z increases 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

49. 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 At high z, galaxy bias depends on luminosity: luminous galaxies are spatially segregated with respect to DM Luminous galaxies do not form in underdense regions

50. Some Preliminary Results New population of galaxies at high z Le Fèvre et al. 2005 Nature in press, Le Fèvre et al. 2005 Evolution of the luminosity Function up to z=2 Ilbert et al 2005 (astro-ph/0409134) A&A in press, Ilbert et al 2005 (astro-ph/0409134) Evolution of the luminosity function per morphological types up to z=1.5 Zucca et al. 2005 (astro-ph/0506393) A&A in press, Zucca et al. 2005 (astro-ph/0506393) Evolution of the galaxy correlation function up to z=2 Le Fèvre et al 2005 (astro-ph/0409135) A&A in press, Le Fèvre et al 2005 (astro-ph/0409135) Evolution of non-linar biasing up to z=1.5 Marinoni et al 2005 (astro-ph/0506561) A&A in press, Marinoni et al 2005 (astro-ph/0506561) The @ Brera-Milan K band imaging survey and clustering : A. Iovino Environmental studies at high z and cluster hunting : O. Cucciati Found a cluster at z=1.47 (P76 proposal FORS1 accepted P.I. Marinoni) Clustering : L. Guzzo