Answering Cosmological Questions with The Next Generation of Galaxy SurveysWill Percival (University of Portsmouth)

Answering Cosmological Questions with The Next Generation of Galaxy SurveysWill Percival (University of Portsmouth)

The standard “model” for cosmologyThe standard “model” for cosmology

Remaining questionsRemaining questions

What are the constituents of matter?– undiscovered particles– neutrino masses

Why do we see an accelerating Universe?– vacuum energy density (Einstein’s cosmological constant)– new scalar field / other phenomenon

How does structure form within this background?– large-scale General Relativity deviations?

Why is the Universe homogeneous on large scales?– inflation or other model?– inflation parameters

How do galaxies form and evolve?

What are the constituents of matter?– undiscovered particles– neutrino masses

Why do we see an accelerating Universe?– vacuum energy density (Einstein’s cosmological constant)– new scalar field / other phenomenon

How does structure form within this background?– large-scale General Relativity deviations?

Why is the Universe homogeneous on large scales?– inflation or other model?– inflation parameters

How do galaxies form and evolve?

Current / future surveysCurrent / future surveys

New wide-field camera for the 4m Blanco telescope Currently being moved from Fermilab to site,

Survey due to start autumn 2011 Ω = 5,000deg2 multi-colour optical imaging (g,r,i,z) with link to IR

data from VISTA hemisphere survey 300,000,000 galaxies Aim is to constrain dark energy using 4 probes

LSS/BAO, weak lensing, supernovaecluster number density

Redshifts based on photometryweak radial measurementsweak redshift-space distortions

See also: Pan-STARRS, VST-VISTA, SkyMapper

New wide-field camera for the 4m Blanco telescope Currently being moved from Fermilab to site,

Survey due to start autumn 2011 Ω = 5,000deg2 multi-colour optical imaging (g,r,i,z) with link to IR

data from VISTA hemisphere survey 300,000,000 galaxies Aim is to constrain dark energy using 4 probes

LSS/BAO, weak lensing, supernovaecluster number density

Redshifts based on photometryweak radial measurementsweak redshift-space distortions

See also: Pan-STARRS, VST-VISTA, SkyMapper

Dark Energy Survey (DES)Dark Energy Survey (DES)

VIMOS Public Extragalactic Redshift Survey (VIPERS)VIMOS Public Extragalactic Redshift Survey (VIPERS)

Uses upgraded VIMOS on VLT Ω = 24deg2

100,000 galaxies emission line galaxies: 0.5<z<1.0 insufficient volume for BAO measurement Unique redshift-space distortion science 18,500 redshifts from pre-upgrade data expect ~10,000 redshifts this season see also: FMOS surveys

Uses upgraded VIMOS on VLT Ω = 24deg2

100,000 galaxies emission line galaxies: 0.5<z<1.0 insufficient volume for BAO measurement Unique redshift-space distortion science 18,500 redshifts from pre-upgrade data expect ~10,000 redshifts this season see also: FMOS surveys

Baryon Oscillation Spectroscopic Survey (BOSS)Baryon Oscillation Spectroscopic Survey (BOSS)

New fibre-fed spectroscope now on the 2.5m SDSS telescope

Ω = 10,000deg2

1,500,000 galaxies 150,000 quasars LRGs : z ~ 0.1 – 0.7 (direct BAO) QSOs : z ~ 2.1 – 3.0 (BAO from Ly-α forest)

0.1<z<0.3: 1% dA, 1.8% H

0.4<z<0.7: 1% dA, 1.8% H

z~2.5: 1.5% dA, 1.2% H Cosmic variance limited to z ~ 0.6 : as good as LSS mapping will get with a single

ground based telescope Leverage existing SDSS hardware & software where possible: part of SDSS-III Sufficient funding is in place and project is 1 year into 5 year duration All imaging data now public (DR8 12/01/11) See also: WiggleZ

New fibre-fed spectroscope now on the 2.5m SDSS telescope

Ω = 10,000deg2

1,500,000 galaxies 150,000 quasars LRGs : z ~ 0.1 – 0.7 (direct BAO) QSOs : z ~ 2.1 – 3.0 (BAO from Ly-α forest)

0.1<z<0.3: 1% dA, 1.8% H

0.4<z<0.7: 1% dA, 1.8% H

z~2.5: 1.5% dA, 1.2% H Cosmic variance limited to z ~ 0.6 : as good as LSS mapping will get with a single

ground based telescope Leverage existing SDSS hardware & software where possible: part of SDSS-III Sufficient funding is in place and project is 1 year into 5 year duration All imaging data now public (DR8 12/01/11) See also: WiggleZ

MOS plans for 4m telescopesMOS plans for 4m telescopes

New fibre-fed spectroscope proposed for many 4m telescopes Ω = 5,000deg2 – 14,000deg2

~10,000,000 galaxies auxillary science from “spare fibres” including

– QSO targets– stellar / Milky-Way / galaxy evolution programs

LRGs : z ~ 0.1 – 1.0 ELGs: z~0.5-1.7 alternative option: mag limit

I<22.5 requiring longer exposures Follow-up of current and future

imaging surveys Options include BigBOSS, DESpec,

WEAVE, VXMS, …

New fibre-fed spectroscope proposed for many 4m telescopes Ω = 5,000deg2 – 14,000deg2

~10,000,000 galaxies auxillary science from “spare fibres” including

– QSO targets– stellar / Milky-Way / galaxy evolution programs

LRGs : z ~ 0.1 – 1.0 ELGs: z~0.5-1.7 alternative option: mag limit

I<22.5 requiring longer exposures Follow-up of current and future

imaging surveys Options include BigBOSS, DESpec,

WEAVE, VXMS, …

From BigBOSS NOAO proposalFrom BigBOSS NOAO proposal

MOS plans for 8-10m telescopesMOS plans for 8-10m telescopes

HETDEX 9.2m Hobby-Eberly Telescope with 22 arcminute FoV, new integral field spectrograph (VIRUS) to simultaneously observe 34,000 spatial

elements– Ω = 420deg2

– 1,000,000 Lyman break galaxies– 1.9 < z < 3.5

SUMIRE 8.2m SUBARU Telescope with 1.5deg FoV Imaging survey with HSC Spectroscopic survey with PFS (ex-WFMOS, more cosmology focused)

– Ω ~ 2,000deg2

– ~4,000,000 redshifts– ~0.7 < z < 1.7 (OII or Lyman break galaxies)

HETDEX 9.2m Hobby-Eberly Telescope with 22 arcminute FoV, new integral field spectrograph (VIRUS) to simultaneously observe 34,000 spatial

elements– Ω = 420deg2

– 1,000,000 Lyman break galaxies– 1.9 < z < 3.5

SUMIRE 8.2m SUBARU Telescope with 1.5deg FoV Imaging survey with HSC Spectroscopic survey with PFS (ex-WFMOS, more cosmology focused)

– Ω ~ 2,000deg2

– ~4,000,000 redshifts– ~0.7 < z < 1.7 (OII or Lyman break galaxies)

EuclidEuclid

ESA Cosmic Vision satellite proposal (600M€, M-class mission) 5 year mission, L2 orbit 1.2m primary mirror, 0.5 sq. deg FOV Ω = 20,000deg2 imaging and spectroscopy slitless spectroscopy:

– 100,000,000 galaxies (direct BAO)– ELGs (H-alpha emitters): z~0.5-2.1

imaging:– deep broad-band optical + 3 NIR images– 2,900,000,000 galaxies (for WL analysis)– photometric redshifts

Space-base gives robustness to systematics Final down-selection due mid 2011 nominal 2017 launch date See also: LSST, WFIRST

ESA Cosmic Vision satellite proposal (600M€, M-class mission) 5 year mission, L2 orbit 1.2m primary mirror, 0.5 sq. deg FOV Ω = 20,000deg2 imaging and spectroscopy slitless spectroscopy:

– 100,000,000 galaxies (direct BAO)– ELGs (H-alpha emitters): z~0.5-2.1

imaging:– deep broad-band optical + 3 NIR images– 2,900,000,000 galaxies (for WL analysis)– photometric redshifts

Space-base gives robustness to systematics Final down-selection due mid 2011 nominal 2017 launch date See also: LSST, WFIRST

How does dark energy affect the geometry?How does dark energy affect the geometry?

Using clustering to measure geometryUsing clustering to measure geometry

Sunyaev & Zel’dovich (1970); Peebles & Yu (1970); Doroshkevitch, Sunyaev & Zel’dovich (1978); Sunyaev & Zel’dovich (1970); Peebles & Yu (1970); Doroshkevitch, Sunyaev & Zel’dovich (1978); Cooray, Hu, Huterer & Joffre (2001); Eisenstein (2003); Seo & Eisenstein (2003); Cooray, Hu, Huterer & Joffre (2001); Eisenstein (2003); Seo & Eisenstein (2003); Blake & Glazebrook (2003); Hu & Haiman (2003); …Blake & Glazebrook (2003); Hu & Haiman (2003); …

Sunyaev & Zel’dovich (1970); Peebles & Yu (1970); Doroshkevitch, Sunyaev & Zel’dovich (1978); Sunyaev & Zel’dovich (1970); Peebles & Yu (1970); Doroshkevitch, Sunyaev & Zel’dovich (1978); Cooray, Hu, Huterer & Joffre (2001); Eisenstein (2003); Seo & Eisenstein (2003); Cooray, Hu, Huterer & Joffre (2001); Eisenstein (2003); Seo & Eisenstein (2003); Blake & Glazebrook (2003); Hu & Haiman (2003); …Blake & Glazebrook (2003); Hu & Haiman (2003); …

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Baryon Acoustic Oscillations (BAO)Baryon Acoustic Oscillations (BAO)

To first approximation, comoving BAO wavelength is determined by the comoving sound horizon at recombination

To first approximation, comoving BAO wavelength is determined by the comoving sound horizon at recombination

comoving sound horizon ~110h-1Mpc, BAO wavelength 0.06hMpc-1 comoving sound horizon ~110h-1Mpc, BAO wavelength 0.06hMpc-1

(images from Martin White)

Varying rs/DV

projection onto the observed galaxy distribution depends onprojection onto the observed galaxy distribution depends on

Predicted BAO constraintsPredicted BAO constraints

Uses public code to estimate errors Uses public code to estimate errors from BAO measurements from Seo & from BAO measurements from Seo & Eisenstein (2007: astro-ph/0701079)Eisenstein (2007: astro-ph/0701079)

Uses public code to estimate errors Uses public code to estimate errors from BAO measurements from Seo & from BAO measurements from Seo & Eisenstein (2007: astro-ph/0701079)Eisenstein (2007: astro-ph/0701079)

Current large-scale galaxy clustering measurementsCurrent large-scale galaxy clustering measurements

SDSS LRGs at z~0.35

The largest volume of the Universe currently mapped

Total effective volumeVeff = 0.26 Gpc3h-3

SDSS LRGs at z~0.35

The largest volume of the Universe currently mapped

Total effective volumeVeff = 0.26 Gpc3h-3

Percival et al. 2009; arXiv:0907.1660Percival et al. 2009; arXiv:0907.1660

Power spectrum gives amplitude of Fourier modes, quantifying clustering strength on different scales

Power spectrum gives amplitude of Fourier modes, quantifying clustering strength on different scales

Predicted galaxy clustering measurements by EuclidPredicted galaxy clustering measurements by Euclid

20% of the Euclid data, assuming the slitless baseline at z~1

Total effective volume (of Euclid)Veff = 19.7 Gpc3h-3

20% of the Euclid data, assuming the slitless baseline at z~1

Total effective volume (of Euclid)Veff = 19.7 Gpc3h-3

ΛCDM models with curvature flat wCDM models

Union supernovae

WMAP 5year

SDSS-II BAO Constraint on rs(zd)/DV(0.2) & rs(zd)/DV(0.35)

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Current BAO constraints vs other dataCurrent BAO constraints vs other data

Percival et al. 2009; arXiv:0907.1660Percival et al. 2009; arXiv:0907.1660

ΛCDM models with curvature flat wCDM models

Union supernovae

WMAP 5year

SDSS-II BAO Constraint on rs(zd)/DV(0.2) & rs(zd)/DV(0.35)

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How does Euclid BAO compare?How does Euclid BAO compare?

Effect of galaxy type & densityEffect of galaxy type & density

Effect of VolumeEffect of Volume

How does structure form within this background?How does structure form within this background?

We cannot see growth of structure directly from galaxiesWe cannot see growth of structure directly from galaxies

satellite galaxies in larger mass objects

central galaxies in smaller objects

large scale clustering strength = number of pairs

typical survey selection gives changing halo mass

Redshift-Space DistortionsRedshift-Space Distortions

When we measure the position of a galaxy, we measure its position in redshift-space; this differs from the real-space because of its peculiar velocity:

When we measure the position of a galaxy, we measure its position in redshift-space; this differs from the real-space because of its peculiar velocity:

Where s and r are positions in redshift- and real-space and vr is the peculiar velocity in the radial direction

Where s and r are positions in redshift- and real-space and vr is the peculiar velocity in the radial direction

Galaxies act as test particlesGalaxies act as test particles

Galaxies act as test particles with the flow of matterGalaxies act as test particles with the flow of matter

On large-scales, the distribution of galaxy velocities is unbiased provided that the positions of galaxies fully sample the velocity field

On large-scales, the distribution of galaxy velocities is unbiased provided that the positions of galaxies fully sample the velocity field

If fact, we can expect a small peak velocity-bias due to motion of peaks in Gaussian random fields

If fact, we can expect a small peak velocity-bias due to motion of peaks in Gaussian random fields

Percival & Schafer, 2008, MNRAS 385, L78Percival & Schafer, 2008, MNRAS 385, L78

UnderUnder--

densitdensityy

Over-Over-densitdensit

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ActualActualshapeshape

ApparentApparentshapeshape

(viewed from (viewed from below)below)

UnderUnder--

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Standard measurements provide good test of modelsStandard measurements provide good test of models

Blake et al, 2010: arXiv:1003.5721Blake et al, 2010: arXiv:1003.5721

Standard assumption: bv=1 (current simulations limit this to a 10% effect).Standard assumption: bv=1 (current simulations limit this to a 10% effect).

assume: irrotational velocity field due to structure growth, plane-parallel approximation, linear deterministic density & velocity bias, first order in δ, θassume: irrotational velocity field due to structure growth, plane-parallel approximation, linear deterministic density & velocity bias, first order in δ, θ

Normalise RSD to σvNormalise RSD to σv

Normalise RSD to fσ8Normalise RSD to fσ8

Normalise RSD to β=f/bNormalise RSD to β=f/b assume continuity, scale-independent growth

assume continuity, scale-independent growth

Expected errors for current / future surveysExpected errors for current / future surveys

White, Song & Percival, 2008, MNRAS, 397, 1348White, Song & Percival, 2008, MNRAS, 397, 1348

Code to estimate errors on fσCode to estimate errors on fσ88 is is available from:available from:http://mwhite.berkeley.edu/Redshift

Code to estimate errors on fσCode to estimate errors on fσ88 is is available from:available from:http://mwhite.berkeley.edu/Redshift

Effect of galaxy type & densityEffect of galaxy type & density

Effect of galaxy VolumeEffect of galaxy Volume

SummarySummary

Galaxy clustering will help to answer remaining questions for astrophysical and cosmological models

Shape of the power spectrum– measures galaxy properties (e.g. faint red galaxies)– neutrino masses (current systematic limit)– models of inflation

Baryon acoustic oscillations – measures cosmological geometry

Redshift-space distortions– measures structure formation

Future MOS instruments on 4m-class telescopes– niche between current experiments and satellite missions– getting sufficient volume is key (>5,000deg2)– redshifts of ELGs will come from OII emission line– colour selection and target sample are key– exciting developments over the next 10—20 years

Galaxy clustering will help to answer remaining questions for astrophysical and cosmological models

Shape of the power spectrum– measures galaxy properties (e.g. faint red galaxies)– neutrino masses (current systematic limit)– models of inflation

Baryon acoustic oscillations – measures cosmological geometry

Redshift-space distortions– measures structure formation

Future MOS instruments on 4m-class telescopes– niche between current experiments and satellite missions– getting sufficient volume is key (>5,000deg2)– redshifts of ELGs will come from OII emission line– colour selection and target sample are key– exciting developments over the next 10—20 years