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Large-scale structure from 2dFGRS. John Peacock IAU 216 Sydney July 2003. The distribution of the galaxies. 1930s: Hubble proves galaxies have a non-random distribution 1950s: Shane & Wirtanen spend 10 years counting 1000,000 galaxies by eye

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Large scale structure from 2dfgrs

Large-scale structure from 2dFGRS

John Peacock IAU 216 Sydney July 2003


The distribution of the galaxies
The distribution of the galaxies

1930s:

Hubble proves galaxies have a non-random distribution

1950s:

Shane & Wirtanen spend 10 years counting 1000,000 galaxies by eye

- filamentary patterns?


Results from the 2df galaxy redshift survey

Results from the 2dF Galaxy Redshift Survey

Target: 250,000 redshifts to B<19.45 (median z = 0.11)

250 nights AAT 4m time

1997-2002


The 2dfgrs team

Australia Joss Bland-Hawthorn Terry Bridges Russell Cannon Matthew Colless Warrick Couch Kathryn Deeley Roberto De Propris Karl Glazebrook Carole Jackson Ian Lewis Bruce Peterson Ian Price Keith Taylor

BritainCarlton Baugh Shaun Cole Chris Collins Nick Cross Gavin Dalton Simon Driver George Efstathiou Richard Ellis Carlos Frenk Ofer Lahav Stuart Lumsden Darren Madgwick Steve Maddox

The 2dFGRS Team

Stephen Moody Peder Norberg John Peacock Will Percival Mark Seaborne Will Sutherland Helen Tadros

33 people at 11 institutions



2dfgrs input catalogue
2dFGRS input catalogue

  • Galaxies: bJ  19.45 from revised APM

  • Total area on sky ~ 2000 deg2

  • 250,000 galaxies in total, 93% sampling rate

  • Mean redshift <z> ~ 0.1, almost all with z < 0.3


2dfgrs geometry
2dFGRS geometry

~2000 sq.deg.

250,000 galaxies

Strips+random fields ~ 1x108 h-3 Mpc3

Volume in strips ~ 3x107 h-3 Mpc3

NGP

SGP

NGP 75x7.5 SGP 75x15 Random 100x2Ø

~70,000 ~140,000 ~40,000


Final 2dFGRS Sky Coverage

NGP

SGP

Final redshift total: 221,283


2dfgrs redshift distribution
2dFGRS Redshift distribution

  • N(z) Still shows significant clustering at z < 0.1

  • The median redshift of the survey is <z> = 0.11

  • Almost all objects have z < 0.3.



Spectrum of inhomogeneities
Spectrum of inhomogeneities

r

x

Primordial power-law spectrum (n=1?)

Transfer function


Transfer function

Key scales:

* Horizon at zeq : 16 (Wmh2)-1 Mpc (observe Wmh)

* Free-stream length : 80 (M/eV)-1 Mpc (Wm h2 = M / 93.5 eV)

* Acoustic horizon : sound speed < c/31/2

* Silk damping

M sets damping scale - reduced power rather than cutoff if DM is mixed

Generally assume adiabatic

Transfer function

Parameters: WdWbWvWneutrino h w n M


2dfgrs power spectrum results
2dFGRS power-spectrum results

Dimensionless power:

d (fractional variance in density) / d ln k

Percival et al. MNRAS 327, 1279 (2001)


Confidence limits
Confidence limits

Wmh = 0.20 ± 0.03

Baryon fraction = 0.15 ± 0.07

‘Prior’:

h = 0.7 ± 10%

&

n = 1



Model fits feb 2001 vs final
Model fits: Feb 2001 vs ‘final’

Wmh = 0.20 ± 0.03

Baryon fraction = 0.15 ± 0.07

Wmh = 0.18 ± 0.02

Baryon fraction = 0.17 ± 0.06

if n = 1: or Wmh = 0.18 e1.3(n-1)


Conclusions from p k
Conclusions from P(k)

  • Lack of oscillations. Must have collisionless component

  • CDM models work

  • Low density if n=1 and h=0.7 apply

  • possibilities for error:

    • Isocurvature?

    • W=1 plus extra ‘radiation’?

    • Massive neutrinos?

    • Scale-dependent bias? (assumed dgalsdmass)


Photometric recalibration
Photometric recalibration

Start with SuperCosmos UKST scans

SDSS overlap in 33 equatorial plates: rms D = 0.09 mag ( = D SDSS-MGC )

Force uniform optical and opt-2MASS colours: rms linearity and ZP corrections 1.4% and 0.15 mag

Calibration good to <1% and <0.03 mag

 recalibrate APM (rms 0.14 mag)


2dfgrs in c o l o u r
2dFGRS in COLOUR

passive

R magnitudes from

SuperCosmos

active

Rest-frame colour gives same information as spectral type, h, but to higher z


Power spectrum and galaxy type
Power spectrum and galaxy type

shape independent of galaxy type within error on spectrum


Relation to cmb results
Relation to CMB results

curvature

baryons

total density

Combining LSS & CMB breaks degeneracies:

LSS measures Wmh only if power index n is known

CMB measures n and Wmh3 (only if curvature is known)


2dfgrs cmb flatness
2dFGRS + CMB: Flatness

CMB alone has a geometrical degeneracy: large curvature is not ruled out

Adding 2dFGRS power spectrum forces flatness:

| 1 - Wtot | < 0.04

Efstathiou et al. MNRAS 330, L29 (2002)



Detailed constraints for flat models cmb 2dfgrs only no priors
Detailed constraints for flat models(CMB + 2dFGRS only: no priors)

Preferred model is scalar-dominated and very nearly scale-invariant

Percival et al. MNRAS 337, 1068 (2002)




likelihood contours post-WMAP + 2dFGRS 147024 gals

scalar only, flat models

- WMAP reduces errors by factor 1.5 to 2



Vacuum equation of state p w r c 2
Vacuum equation of state (P = w rc2)

w shifts present horizon, so different Wm needed to keep CMB peak location for given h

w < - 0.54

similar limit from Supernovae: w < - 0.8 overall

2dFGRS


Extra relativistic components
Extra relativistic components?

Matter-radiation horizon scale depends on matter density (Wmh2) and relativistic density (=1.68 rCMB for 3 light neutrinos).

Suppose rrel = X (1.68 rCMB ) so apparent Wmh = Wmh X-1/2 and Wm=1 h=0.5 works if X=8

But extra radiation affects CMB too. Maintaining peak location needs h=0.5X1/2 if Wm=1

If w=-1, 2dFGRS+CMB measureh X-1/2 = 0.71 +- 5% with HST h = 0.72 +- 11%, hence

1.68X = 1.70 +- 0.24 (3.1 +- 1.1 neutrinos)


Summary
Summary

  • >10 Mpc clustering in good accord with LCDM

    • power spectrum favours Wm h= 0.18 & 17% baryons

  • CMB + 2dFGRS implies flatness

    • CMB + Flatness measures Wm h3.4 = 0.078

    • hence h = 0.71 ± 5%, Wm = 0.26 ± 0.04

  • No evidence for tilt (n = 0.96 +- 0.04) or tensors

    • But large tensor fractions not yet strongly excluded

  • Neutrino mass <0.6 eV if Wm =1 excluded

  • w < - 0.54 by adding HST data on h (agrees with SN)

  • Boosted relativistic density cannot save Wm =1

    • Neutrino background detected if w = -1

  • Data public: http://www.mso.anu.edu.au/2dFGRS/Public


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