Large scale structure beyond the 2df galaxy redshift survey
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Large-Scale Structure beyond the 2dF Galaxy Redshift Survey. Gavin Dalton Kyoto FMOS Workshop January 2004 (Oxford & RAL) . Overview. Summary of 2dFGRS design Key results… defining contemporary cosmology

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Large scale structure beyond the 2df galaxy redshift survey

Large-Scale Structure beyond the 2dF Galaxy Redshift Survey

Gavin Dalton Kyoto FMOS Workshop January 2004 (Oxford & RAL)


Overview
Overview

  • Summary of 2dFGRS design

  • Key results… defining contemporary cosmology

  • Key results… galaxies as tracers of LSS

  • Key results… relationship to CMB measurements

  • FMOS Possibilities – LSS beyond z=1

  • Input data: Wide-Field IR imaging surveys

  • Survey Design Issues


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


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.



Fine detail 2 deg ngp slices 1 deg steps
Fine detail: 2-deg NGP slices (1-deg steps)

2dFGRS: bJ < 19.45

SDSS: r < 17.8


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)


Redshift space clustering

r

Redshift-space clustering

s

p

  • z-space distortions due to peculiar velocities are quantified by correlation fn (,).

  • Two effects visible:

    • Small separations on sky: ‘Finger-of-God’;

    • Large separations on sky: flattening along line of sight


Fit quadrupole/monopole ratio of (,) as a function of r with model having 0.6/b and p (pairwise velocity dispersion) as parameters

Model fits to z-space distortions

 and 

 = 0.4, p= 300,500

  • Best fit for r>8h-1Mpc (allowing for correlated errors) gives:

     = 0.6/b = 0.43  0.07 p =385  50 km s-1

  • Applies at z = 0.17, L =1.9 L* (significant corrections)

 = 0.3,0.4,0.5; p= 400

99%


Galaxy properties spectral classification by pca

Early

PC3

PC2

PC1

Late

Mean spectrum

Galaxy Properties:Spectral classification by PCA

  • Apply Principal Component analysis to spectra.

  • PC1: emission lines correlate with blue continuum.

  • PC2: strength of emission lines without continuum.

  • PC3: strength of Balmer lines w.r.t. other emission.

  • Define spectral types as sequence of increasing strength of emission lines

  • Instrumentally robust

  • Meaning: SFR sequence


Clustering as f l
Clustering as f(L)

Clustering increases at high luminosity:

b(L) / b(L*) = 0.85 + 0.15(L/L*)

suggests << L* galaxies are slightly antibiased

- and IRAS g’s even more so: b = 0.8


Redshift space distortions and galaxy type
Redshift-space distortions and galaxy type

  • Passive:

  •  = m0.6/b = 0.46  0.13 p =618  50 km s-1

  • Active:

  •  = m0.6/b = 0.54  0.15 p =418  50 km s-1

Consistent with Wm = 0.26, bpassive = 1.2, bactive = 0.9


Power spectrum and galaxy type
Power spectrum and galaxy type

shape independent of galaxy type within uncertainty 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)




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


Key points
Key Points

  • Basic underlying cosmology now well determined

  • CMB + 2dFGRS implies flatness

    • CMB + Flatness measures Wm h3.4 = 0.078

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

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

  • Clustering enhanced as F(L)

  • Different bias for different galaxy types, but shape of P(k) is identical.

  • Many diverse science goals realised in a single survey design


Fmos possibilities for lss at z 1
FMOS Possibilities for LSS at z>1

  • Wavelength Range (single exposure) 0.9mm<l<1.8mm

    • OII enters at z=1.4

    • 4000Å break enters at z=1.2

    • Hα enters at z=0.4

    • OII leaves at z=3.8

    • Hα leaves at z=1.74

      Complex p(z) due to atmospheric bands and OH mask.

      New field setup time is FAST

  • Sensitivity: Clear IDs for H=20 magnitude limit:

    20 minutes for late-types

    (50 minutes for early types)

    [But P(k) shape insensitive to type!!!]

  • Could obtain as many as 7000 galaxy spectra/night!


Input data wide field ir surveys
Input Data: Wide-Field IR Surveys

  • Natural starting point is the UKIDSS DXS

    • 35 square degrees to K=21.5, J=22.5 (5)

      ~ 60000 galaxies (zP1, HO20)

UKIDSS fields: 2-year plan

LAS

DXS

UDS

GPS

GCS


Upcoming wide field ir imaging vista
Upcoming wide-field IR imaging - VISTA

1.67 degree focal plane,

16 2048x2048 HgCdTe arrays

Single instrument survey telescope


Vista capabilities
VISTA Capabilities

  • FOV 1.67 degrees

  • Pixel sampling 0.33 arcseconds

  • YJHK filter set as baseline (3 empty slots)

  • 70% of VISTA time must be dedicated to ‘public’ surveys with emphasis on meeting the science goals of the original VISTA consortium

  • Extension of UKIDSS DXS in 1 year would cover 500 square degrees.

  • Commissioning begins April 2006

  • Data processing and archiving in common with UKIDSS – fast access to final catalogues.

  • ESO effectively committed to supporting UKIDSS/VISTA operations with complementary VST surveys.


Fmos survey design issues
FMOS Survey Design Issues

  • Optimal survey speed influenced by reconfiguration and field acquisition times…

    • Possibilities for large-scale surveys with relatively bright limits.

  • Optimal use of telescope time may dictate merged surveys (c.f. 2dF GRS & QSO surveys) with multiple science goals (i.e. evolution; clusters; EROs; SWIRE all may be included in LSS survey).

  • Input data for ambitious surveys will be available on appropriate timescales, but much preparation required.

    • No problem with spreading a large survey over several years since effectively no competition! – e.g. think in terms of a survey of ~100 FMOS nights over 5 years.


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