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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. Christian Marinoni. Centre de Physique Th éorique Université de Provence. Nice 25-27 Jan 2005. Outline. Galaxy bias - Biasing from a theoretical & observational perspective

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

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  1. 9,000,000,000 Years of Gravity at Work in the Cosmic Factory Christian Marinoni Centre de Physique Théorique Université de Provence Nice 25-27 Jan 2005

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

  3. Theoretical Background: Dynamics of matter fluctuations t

  4. 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

  5. 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

  6. 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 

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

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

  9. Where do we stand with observations At high z ,blue galaxies more correlated than matter

  10. Where do we stand with observations Extremely red objects at z~1 more clustered w/r to blue

  11. Where do we stand with observations

  12. Where do we stand with observations Conflicting evidences about biasing evolution!

  13. Outline • 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)

  14. The : Vimos-VLT Redshift Survey • French-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

  15. The in a nutshell 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 McCracken et al 2004, Radovich et al. 2004, Iovino 2005 2 6 Spectroscopic Survey (Vimos at VLT): • Purelyflux -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 LeFèvre et al 2004 AA in press (astroph/0409133) Public data release on http://cencosw.oamp.fr

  16. Sample: Deep “cone” (2h Field: first-epoch data) z=1.5 • ~7000 galaxies with secure redshifts, IAB24 • 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

  17. The Density Field (smoothing R=2Mpc) TheProbabilityDistributionFunction(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() High density Low density  2DFGRS/SDSS stop here

  18. Time Evolution of the galaxy PDF The 1P-PDF of galaxy overdensities g () R • The PDF is different • at different cosmic • epochs Z=1.1-1.5 Z=0.7-1.1 • 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

  19. A possible Interpretation Gravitational instability in an expanding universe ???

  20. Lognormal! (Coles & Jones 1991) The PDF of mass overdensities f(): Shape Conclusion: Galaxies are Spatially distributed in a different way (biased) with respect to dark matter at high z Z=1.1-1.5 Z=0.7-1.1

  21. Measuring the galaxy bias up to z=1.5 with the VVDS Bias: difference in distribution of DM and galaxy fluctuations Linear Bias Scheme: (Kaiser 1984) • Redshift evolution • Non linearity • Scale dependence Our goal: Sigad et al 2000 Marinoni & Hudson 2002 Ostriker et al. 2003 Strategy • Derive the biasing function

  22. The PDF of galaxy overdensities g(): Shape Z=1.1-1.5 Z=0.7-1.1

  23. The biasing function: Time evolution • Scale independent • on 5 < R(Mpc) < 10 2dF • Galaxies were • progressively more • biased mass tracers • in the past (Norberg et al. 04) • Evolution: • weak for z < 0.8 • stronger for z > 0.8

  24. The biasing function: 2) Shape b() L 15 Mpc Smoothing • Non linearity at a level <10% on scales 5<R<10 Mpc • (Local slope is steeper (bias stronger) in underdense regions) • 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

  25. 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

  26. 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

  27. Theoretical Interpretation: Which is the physical mechanism governing biasing evolution? Merging (Mo & White `96 Matarrese et al `97) Istantaneous Star Formation (Blanton et al `02) Gravity (Dekel and Rees `88 Tegmark & Peebles `98)

  28. Outline • 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

  29. Test of the Gravitational Instability Paradigm ~ costant with z decrease with z Volume limited sample M<-20+5log h

  30. Test of the Gravitational Instability Paradigm Peebles 1980 Juskiewicz et al. 1993

  31. Conclusions • 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). • 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. • 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

  32. Reconstruction Completeness

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

  34. 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?

  35.  r -1 Growth of Cosmic Structures Fundamental variable for LSS studies: The Matter Fluctuation Field The Evolution of the LSS in linear approximation...... Continuity eq. + Poisson eq. + Poisson eq. Initial Condition: Primordial Power Spectrum Assume knowledge of cosmological background Friedmann eq. SNIa+Wmap measurements Harrison Zel’dovich.

  36. Reconstruction of the Galaxy Density Field • 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)

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

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