answering cosmological questions with the next generation of galaxy surveys will percival...
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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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Over-Over-densitdensit
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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