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Large-Scale Structure beyond the 2dF Galaxy Redshift SurveyPowerPoint Presentation

Large-Scale Structure beyond the 2dF Galaxy Redshift Survey

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### Large-Scale Structure beyond the 2dF Galaxy Redshift Survey

### Results from the 2dF Galaxy Redshift Survey

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

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

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

250 nights AAT 4m time

1997-2002

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.

2dFGRS power-spectrum results

Dimensionless power:

d (fractional variance in density) / d ln k

Percival et al. MNRAS 327, 1279 (2001)

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

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%

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 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

- 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

shape independent of galaxy type within uncertainty on spectrum

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

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 pre-WMAP + 2dFGRS 147024 gals

scalar only, flat models

likelihood contours post-WMAP + 2dFGRS 147024 gals

scalar only, flat models

- WMAP reduces errors by factor 1.5 to 2

likelihood contours post-WMAP + 2dFGRS 213947gals

scalar only, flat models

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

- 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

- 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

- Natural starting point is the UKIDSS DXS
- 35 square degrees to K=21.5, J=22.5 (5)
~ 60000 galaxies (zP1, HO20)

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

UKIDSS fields: 2-year plan

LAS

DXS

UDS

GPS

GCS

Upcoming wide-field IR imaging - VISTA

1.67 degree focal plane,

16 2048x2048 HgCdTe arrays

Single instrument survey telescope

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

- 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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