History of cosmic History of cosmic

web web of galaxies of galaxies

Agnieszka Pollo

Laboratoire d'Astrophysique de Marseille (LAM)Marseille, France

Short History of the Universe (one of)

Planck Era: 10^(-43) s. ~ 10^(-33) cm regions homogeneous and isotropic. izotropowe, T=10(^32)K.

• Inflation. 10^(-35) s after BB, T = 10^(27) – 10^(28)K, fast expansion.

• Inflation ends. 10^(-33 s), T= 10^(27) – 10^(28)K. Homogeneous regions from Planck era have grown to~ 100 cm (> 10^(35) times). Tiny nearly gaussian density fluctuations.

Short History of the Universe•Bariogenesis. 100,000,001 protons per 100,000,000 antiprotons (and 100,000,000 photons). •Till 100 s after BB: Universe grows and cools down, T ~ 10^9K. Protons anihillate with antiprotons, later e- and e+. H i He are created.

Krótka historia Wszechświata• One month after BB: processes which

transform radiation field into black body radiation become slower than the velocity of expansion of the Universe; from now on there is a chance of some informations being preserved in CMB 56 000 years after BB: matter density= radiation density. T = 9000 K. Inhomogeneities of (dark) matter start to grow…

Short history of the Universe• 380 000 after BB: protons and electrons

make neutral H. T=3000K. The Universe becomes transparent - CMB may travel freely (last scattering surface). “Normal” (barionic) matter starts to accumulate on the dark matter overdensities…

• 100-200 mln years after BB: first stars shine and re-ionize the Universe. First supernovae explode. Galaxies and clusters form.

• 4,6 bln years ago: Sun shines. • Today: 13.7 bln years after BB. T=2.725

K.

After recombination (WMAP 3-years temperature map)

Large-scale structure in the local (z<0.2) Universe: galaxies (Colless, Maddox, Peacock et al.)

The Large Scale Structure of the Universe• Gravitational instability theory:

– Density fluctuations (of dark matter) after inflation, Gaussian (?) distribution

– Matter gathers around these

– Galaxies, clusters, LSS form• The smaller scale the more non-linear evolution• Tests of the model

• Statistics• Simulations

From the observational side...

• The main source of our knowledge about the LSS of the Universe are catalogs of galaxies (2D – positions only and 3D – redshift surveys)

Redshift surveys may allow to investigate...

• The history of formation and evolution of galaxies

• Evolution of the LSS of the Universe and what physical processes may determine it in different epochs and timescales

• Formation and evolution of different classes of objects (e.g. AGNs)

• Formation and evolution of clusters

Most of great calalogs today: only local Universe

• Local Universe – a few big surveys, like • SDSS

• 2dF

• > 1M galaktyk do z = 0.3

• Distribution and properties relatively easy to examine

• BUT: no evolution

• A possibility of testing new cosmological models• BUT: practical problems: observed galaxies are worse

and worse tracers of mass; evolution of galaxies themselves; bias is a function of z redshift!

• This is different with respect to local surveys where the “observation time” << Hubble time

• Deep surveys: structure evolution and galaxy evolution and evolution of subsequent population of stars in galaxies…

• A few years ago: the biggest available deep surveys were small small fields, few galaxies (~1000) (e.g. CFRS, Le Fevre et al.1996; CNOC, Yee et al 1998): different selection criteria (color)- Effect: ro from 2 to 5 h-1 Mpc for z between 0 and 5 (see Steidel 1998)

Large Scale Structure of the Universe Large Scale Structure of the Universe with deep surveyswith deep surveys

Which means practical problems:

• Few objects (until recently not more than a few*1000 for 0.5<z<5)

• Small volumes (->big cosmic variance) • Different selection criteria for different

measurements and related biases; how to compare? How to make a joint analysis?

Borgani & Guzzo 2001

Structure evolution: we want to see the whole movie, not only the last slide!

Recent deep galaxy surveys• Goalç to measure redshifts of > 100 000

galaxies, to analyse history of LSS and galaxies themselves– VVDS

– Deep-2

– ostatnio: COSMOS

• Well defined (and low) limiting luminosity (e.g. m_I>22).

• Large fields to minimize cosmic variance (to reach volumes ~100 h-1 Mpc)

• Redshift measurements deep enough to probe LSS• To understand the biases:

• Multi-band information • High-resolution imaging (e.g. HST)

How to plan a deep (z~1) survey, to How to plan a deep (z~1) survey, to investigate LSS in a credible way?investigate LSS in a credible way?

The VIRMOS Consortium: France-Italy collaboration

ORIGINAL PLAN: building VIMOS: (Visible: 0.37-1 ,

shipped to Chile in Oct 2001; FULLY OPERATIVE NOW

NIRMOS (NIR: 1-2 ; CANCELLED

The VI(R)MOS projectThe VI(R)MOS project((VVisible and isible and IInfranfraRRed ed MMulti-ulti-OObject bject SSpectrographs pectrographs for the for the ESO VLTESO VLT))

The origins: build a redshift machine The origins: build a redshift machine for the ESO VLT targeted to deep, for the ESO VLT targeted to deep,

high-surface density galaxy sampleshigh-surface density galaxy samples

• 1995: First ideas: WFIS+NIRMOS• 1996: Feasibility Study• 1997: VIMOS+NIRMOS contract:VIisible Multi -Object Spectrograph +

Near InfraRed Multi -Object Spectrograph

Who’s Who in the the Who’s Who in the the Consortium Consortium

• Six main nodesSix main nodes: Marseille, Bologna, Haute-Provence, Milan, Naples, Toulouse

• PI’sPI’s: O. Le Fevre & G.Vettolani • co-I’sco-I’s: D. Maccagni (Milano), J.P. Picat (Toulouse), D. Mancini

(Naples)• Science Advisory CommitteeScience Advisory Committee• + 50 people involved in the Hardware/Software Team • + 90 people involved in the Science Team for the survey

preparation and analysis• See web page, www.oamp.fr/virmos See web page, www.oamp.fr/virmos

• Science drive: the VIMOS-VLT Deep Science drive: the VIMOS-VLT Deep Survey (VVDS)Survey (VVDS):

•50 VIMOS guaranteed nights over ~3 years on ESO-VLT UT3

•100,000 redshifts to IAB<22 over an area of ~16 sq.deg., 0<z<1.3 in 5 fields

•50,000 redshifts to 22<IAB<24 over an area of ~1.5 sq.deg., 0<z<5

•~1000 redshifts to IAB~26 over a 1x1 sq.arcmin area using a Integral Field Spectroscopy unit (6400 fibres)

• Preparatory IMAGINGPreparatory IMAGING:

• UBVRIJK photometric surveys at CFHT, ESO, CTIO

• RADIO (VLA@1.4GHz, ~80 mJy) + X-ray (XMM, ~1014 erg s-1 cm-2 for extended sources) coverage of the F02 field (deep 1 sq.deg. area at RA=02h)

• X-ray (XMM) imaging to fx ~ 10-15 erg s-1 cm-2 over F02

VIMOS/NIRMOS layoutVIMOS/NIRMOS layout

VLT Nasmith focus flattened separately into 4 channels, fed into 4 CCD cameras (7x8 arcmin field of view each)

Focal Plane Adapter Lenses

A redshift machine: > 500 spectra in one A redshift machine: > 500 spectra in one shotshot

FOV: 4x56 sq arcmin

multiplexing 800

spectral resolution: 200 -5000

IFU 1'x 1', 6400 fibres

• 2-point correlation function in redshift slices

• Clustering per color, luminosity, spectral types

• Bias evolution

• Clustering of particular types of objects (EROS, star’forming galaxies) as compared to general population

• Galaxy mergers: how many close pairs in different epochs?

•redshift-space CF distortions -> small-scale galaxy dynamics

•Clusters density Xray (XMM) and optical (multi-colour, I-K, matched filter, photo-z,…)

… and many more...

VVDS and structure evolution:VVDS and structure evolution:

First Epoch VVDS Data

• 11564 spectra from 17.5<IAB<24, fields 0226-04 and CDFS, area 0.61 sq.deg.– 10518 galaxies with measured z,

8869 with “confidence level” >80%– 836 stars– 85 AGNs– 125 unidentified objects

• Field coverage 25% - 30%

First epoch VVDS-Deep survey: VVDS-02 field

First VVDS data

• 0<z<5• 1065 galaxies z>1.4

– Successful measurements on the redshift desert , i.e. 1.5<z<2.2

– Problems in 2.2<z<2.7 range (because of the filter coverage)

Distribution of “secure” redshifts (median 0.70)

2-point correlation function• Definition: probability “above random” that we find a

pair of galaxies at a certain distance from each other (spatial, angular…)

• In practice: different estimators, e.g. Landy-Szalay

• Problems: different densities of different parts of the fields because of different number of observation runs, bright stars, non-random choice of objects for spectroscopy…

Measuring the correlation function

Biases removal for the redshift-space correlation function

Biases removal for the 2D redshift space correlation function

Biases removal for the projected (real space) correlation function

Pollo et al, 2005 and Le Fevre, et al. 2005

Evolution of the 2-point correlation function from the first-epoch VVDS data

(astro-ph/0409135)

Evolution of a comoving correlation length

Comparison with DEEP-2

(astro-h/0409135)

What theory says? Weinberg at al., 2004, LCDM simulations: clustering history of galaxies and DM differs dramatically

SDSS (Zehavi et al)

2dFGRS

VVDS ~L* galaxies at z~1.1

Similar informations may be extracted directly from PDF…

Ilbert & VVDS team 2004

Luminosity function evolves, too…Luminosity function evolves, too…

Red (“old”) galaxies and blue (recently star forming) galaxies

• Now it is well known that red/early type galaxies (elipticals, irregulars) are more clustered than blue/late type (spiral) ones

• How did it evolve? When did they segregate?• When did galaxy types appear?

• Meneux et al., 2006, Cucciati et al. 2006

Correlation length for different galaxy types and colors

CF properties vs absolute luminosities

• w_p(r_p) in different luminosity ranges for small and large z

• Correlation length r_0• slope gamma• Non power-law fit!• Different relative bias at different scales

w_p in luminosity ranges

• VVDS-02, M_B• 2 “wide” ranges

corresponding to ~3.5 bld years, medians z~0.4 and z~0.9

• 7 luminosity ranges in each

w_p(r_p) and the best (r_0, gamma)

w_p(r_p) – power-law fit

r_0: VVDS vs SDSS and 2dF

05

1015

Tit olo pr in-cipale

Co lon n a 1

Co lon n a 2

Co lon n a 3

gamma: VVDS vs SDSS i 2dF

Relative bias at 1 Mpc scale

No power law… Argument for Halo Occupation Distribution Models...

...non-linear relative relative bias(with rescpect to gal L*)?

• General populationç correlation length almost constant between z=0.5 and z~2, in a survey where the only selection criterion is luminosity (IAB<24)

• This effects may be understood as a superposition of the evolution of structure itself,evolution of bias and different dependence of clustering on luminosity

•Generaal population: in a good agreement with hydrodynamical simulations in a model with CMB and big cosmological constant

•Galaxies of early spectral types (eliptical and early spirals) are more clustered than late spirals and irregulars in all epochs

•Red galaxies more correlated than blue ones

•But: a tendency to reverse this relation at z~1.5?

Summary – structure evolution in VVDSSummary – structure evolution in VVDS

• For different absolute luminosities

•r_0 and gamma rise for L>L* for large z

• non power law fit of CF z -> argument in favor of HOD models?

•Scale-dependent bias?

•Conclusions:

•In the z~0.9 Universe bright galaxies more willingly were closer to other bright galaxies than today

•What happened to them? Did they merge? Did they get fainter?

•Bias not only evolving, but also non-linear?

•We have to develop models and theory

Summary – structure evolution in VVDSSummary – structure evolution in VVDS

•

• Survey description (Le Fevre et al. 2005)

• Two-point correlation function in z slices (Le Fevre et al., 2005, Pollo et al., 2005, A & A)

• Evolution of LF and B luminosity density (Ilbert et al. 2005, Tresse et al. 2005, Zucca et al. 2005)

• Combined GALEX-VVDS evolution of UV LF and UV luminosity density (Arnouts et al. 2005, Schiminovich et al 2005)

• Clustering of color-selected classes (Meneux et al, 2006. A&A, in press)

• Clustering as a function of luminosity (Pollo et al., 2006a, A&A, in press, Pollo et al., 2006b, in prep.)

• Evolution of bias (Marinoni et al., 2005)

• Properties of K-selected galaxies in the VVDS-Deep survey (Iovino et al., A&A, in press)

First epoch VVDS results (selected):First epoch VVDS results (selected):

An example of An example of finding high-finding high-redshift galaxies: redshift galaxies: the Ly-break the Ly-break techniquetechnique

Effective in isolating galaxies around z~3 (U-dropouts) and z~4 (B-dropouts) Pioneered by Steidel & Hamilton (1992) Spectroscopic confirmation only possible thanks to the new generation of 10m-telescope availability (Keck) Selects strongly star-forming galaxies with significant Lyman break Dickinson 1998Dickinson 1998

H. MacCracken & VIRMOS Consortium

S. Foucaud PhD Thesis, 2003

Ly-break galaxies: highly clustered Ly-break galaxies: highly clustered objectsobjects

Correlation length ~3-5 h-1 Mpc, i.e. comparable to today’s normal galaxies!

Lyman-break galaxies are strongly star-forming objects, plausibly progenitors of today’s luminous cluster galaxies.

Clearly, their clustering is not representative of general structure at z=3. They are an illustrative example of a highly biased population of LSS tracers. Similar examples are provided by very red galaxies selected using near-infrared bands around z~1 (R-K) and z>2 (J-K) (e.g. works by Cimatti et al. and Van Dokkum et al.).

Need for larger redshift surveys looking at the global galaxy population.

Two such projects underway: the DEEP2 survey at Keck (Davis et al) and the VIMOS-VLT Deep Survey (VVDS) Governato et al 1999, Nature

Schuecker et al. 2003, REFLEX cosmological constraints

Two-point correlation function from VVDS first-epoch data per galaxy morphological types – example for one z slice

3) Both? (2dF at z~0)3) Both? (2dF at z~0)

• Importance of multi-Importance of multi-colour coveragecolour coverage • HST-ACS in the futureHST-ACS in the future

Borgani & Guzzo 2001

What we expect to find:

2dFGRS Maximum likelihood fit of redshift-space distortions:

β= M0 . 6

b0 . 43 0 . 07

b 1 M 0 . 3 0 .1

A more recent analysis of the 100,000 redshift public release, with careful treatment of window function aliases and error correlations finds =0.16 (Tegmark, Hamilton & Xu, 2002, astro-ph/0111575)

Morphological Morphological segregation in 2dF segregation in 2dF survey (Norberg et al. survey (Norberg et al. 2002)2002)

What at high z’s ? What at high z’s ? (Benson et al (Benson et al prediction)prediction)

• Two-point correlation function in z slices

• Clustering of color-selected classes

• Clustering of radio-loud vs. normal population

• Evolution of bias (i.e. the way light traces mass)

• Clustering of special classes (e.g. Extremely Red Objects, strongly star-forming galaxies) vs. general population

• Merging history: how many close pairs at different redshifts?

• Small-scale dynamics from redshift-space distortions

• Evolution of number density of galaxy clusters: X-ray selection (XMM survey over 2hrs field) vs. optical selection (multi-colour, I-K, matched filter, photo-z,…)

… and much more

The VIRMOS survey and the evolution of structure:The VIRMOS survey and the evolution of structure:

McCracken & VIRMOS Team

VIRMOS survey expectationsVIRMOS survey expectations

(N-body/semi-analytic simulations by S. Colombi & S. Hatton)

H. MacCracken & VIRMOS Consortium

S. Foucaud PhD Thesis, 2003

Bondi & VIRMOS Consortium, 2002, A&A submitted

CNOC2 survey: 1.5 sq.deg CNOC2 survey: 1.5 sq.deg to R=21.5, ~6000 galaxies to R=21.5, ~6000 galaxies (Yee, Carlberg et al.)(Yee, Carlberg et al.)

Schuecker et al. 2003, REFLEX cosmological constraints

An example of An example of finding high-finding high-redshift galaxies: redshift galaxies: the Ly-break the Ly-break techniquetechnique

Effective in isolating galaxies around z~3 (U-dropouts) and z~4 (B-dropouts) Pioneered by Steidel & Hamilton (1992) Spectroscopic confirmation only possible thanks to the new generation of 10m-telescope availability (Keck) Selects strongly star-forming galaxies with significant Lyman break Dickinson 1998Dickinson 1998

Ly-break galaxies: highly clustered Ly-break galaxies: highly clustered objectsobjects

Correlation length ~3-5 h-1 Mpc, i.e. comparable to today’s normal galaxies!

Lyman-break galaxies are strongly star-forming objects, plausibly progenitors of today’s luminous cluster galaxies.

Clearly, their clustering is not representative of general structure at z=3. They are an illustrative example of a highly biased population of LSS tracers. Similar examples are provided by very red galaxies selected using near-infrared bands around z~1 (R-K) and z>2 (J-K) (e.g. works by Cimatti et al. and Van Dokkum et al.).

Need for larger redshift surveys looking at the global galaxy population.

Two such projects underway: the DEEP2 survey at Keck (Davis et al) and the VIMOS-VLT Deep Survey (VVDS) Governato et al 1999, Nature

<z>=0.5

<z>=0.7

<z>=1.0

<z>=0.6

<z>=0.8

<z>=1.2

Can we understand the evolution of bias? Can we understand the evolution of bias? 1) Clustering as a function of morphology1) Clustering as a function of morphology

Guzzo, Strauss, Fisher et al. 1997

Clustering depends on luminosityClustering depends on luminosity