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 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

Target: 250,000 redshifts to B<19.45

(median z = 0.11)

250 nights AAT 4m time

1997-2002

SGP

Final 2dFGRS Sky Coverage

NGP

Final redshift total: 221,283

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.

Cone diagram: 4-degree wedge

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

2dFGRS: bJ < 19.45

SDSS: r < 17.8

2dFGRS power-spectrum results

Dimensionless power:

d (fractional variance in density) / d ln k

Percival et al. MNRAS 327, 1279 (2001)

Confidence limits

‘Prior’:

h = 0.7 ± 10%

&

n = 1

mh = 0.20 ± 0.03

Baryon fraction = 0.15 ± 0.07

Power spectrum: Feb 2001 vs ‘final’

Model fits: Feb 2001 vs ‘final’

mh = 0.20 ± 0.03

Baryon fraction = 0.15 ± 0.07

mh = 0.18 ± 0.02

Baryon fraction = 0.17 ± 0.06

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

Redshift-space clustering

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

r

and Fit quadrupole/monopole ratio of

(,) as a function of r with model having 0.6/b and p (pairwise velocity dispersion) as parameters

Best fit for r > 8 h-1 Mpc (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)

Model fits to z-space distortions

= 0.3,0.4,0.5; p= 400

= 0.4, p= 300,500

99%

Mean spectrum

PC1

PC2

PC3 Early

Late

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 m = 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

Combining LSS & CMB breaks degeneracies:

LSS measures mh only if power index n is known

CMB measures n and mh3 (only if curvature is known)

curvature

total density

baryons

2dFGRS + CMB: Flatness

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

Adding 2dFGRS power spectrum forces flatness:

| 1 - tot | < 0.04

Efstathiou et al. MNRAS 330, L29 (2002)

Impact of WMAP

likelihood contours pre-WMAP + 2dFGRS 147024 galsscalar only, flat models

likelihood contours post-WMAP + 2dFGRS 147024 galsscalar only, flat models- WMAP reduces errors by factor 1.5 to 2

likelihood contours post-WMAP + 2dFGRS 213947galsscalar only, flat models

Vacuum equation of state (P = w c2)

w shifts present horizon, so different m

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 m h3.4 = 0.078

– hence h = 0.71 ± 5%, m = 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) 0.9m<<1.8m

– 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)

UKIDSS fields: 2-year plan

LAS

DXS

UDS

GPS

GCS

Upcoming wide-field IR imaging - VISTA1.67 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.