Using Galaxy Clusters forCosmology and the XCS

Ben Hoyle, Bob Nichol, David Bacon, Ed Lloyd-Davies, Kathy Romer & the XCS

Cape Town April ‘08

OverviewOverview Clusters Clusters & Cosmology Cluster collapse; cosmology Cluster surveys X-ray cluster catalogues The XMM Cluster Survey [XCS] Detecting clusters Cluster classification Redshift estimates High redshift cluster Mass estimate 1; Scaling relations Mass estimate 2; Weak lensing The magnification bias The future

Clusters Clusters & Cosmology Cluster collapse; cosmology Cluster surveys X-ray cluster catalogues The XMM Cluster Survey [XCS] Detecting clusters Cluster classification Redshift estimates High redshift cluster Mass estimate 1; Scaling relations Mass estimate 2; Weak lensing The magnification bias The future

Clusters Clusters

Properties of clusters of galaxies: Size ~ few Mpc Mass Emit broad range of EM Galaxies -> optical ICM -> X-rays

Properties of clusters of galaxies: Size ~ few Mpc Mass Emit broad range of EM Galaxies -> optical ICM -> X-rays

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>1012MΘ

Clusters & cosmologyClusters & cosmologyThe number density and mass of clusters, the mass function, n(M,z), are related to by:

The number density and mass of clusters, the mass function, n(M,z), are related to by:

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n(M,z)dM =2

π0

ρM

d lnσ (M)

d lnMexp(−

ν 2

2)dM

M 2

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ν =δsc

D(z)σ (M)

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δec = δsc (z) 1+ βσ 2

δsc2

⎡

⎣ ⎢

⎤

⎦ ⎥

γ ⎛

⎝ ⎜ ⎜

⎞

⎠ ⎟ ⎟

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Ωm,ΩΛ ,σ 8,ω

• Sheth & Tormen, ellipsoidal collapse

Press & Schechter, spherical collapse

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σ(M)

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δec

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δsc

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D(z)

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σ 8

Parameter Descritption

Function of

Barrier value

Varience of density field

Normalisation Of den. field

Growth of strtucture

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σ 8

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Ωm,ΩΛ ,ω€

Ωm,ΩΛ

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Ωm,ΩΛ

Cluster collapse; cosmologyCluster collapse; cosmologyEllipsodial collapseSpherical collapse

Vary mattercontent

Vary w=const

ModifyGravity

Schaefer & Koyama

Cluster surveysCluster surveysCluster cosmology checklist: Lots of clusters Broad redshift range Mass estimates

Cluster cosmology checklist: Lots of clusters Broad redshift range Mass estimates

Optical cluster catalogues • Large numbers• Redshifts• No masses

X-ray cluster catalogues• Mass estimates:Cavaliere & Fusco-Femiano ’78, Dai et al ’06• Small numbers• Redshifts difficult

X-ray cluster cataloguesX-ray cluster catalogues

X-ray identified cluster catalogues are mainly taken from the literature.

X-ray identified cluster catalogues are mainly taken from the literature.Catalogue Clusters Redshifts? P.I.

XCS ~1800 <10% Romer ‘01

BCS 206 Yes Ebling ‘98

eBCS 107 Yes Ebling ‘02

R400D 242 Yes Burenin ‘02

OverviewOverview Clusters Clusters & Cosmology Cluster collapse; cosmology Cluster surveys X-ray cluster catalogues The XMM cluster survey [XCS] Detecting clusters Cluster classification Redshift estimates High redshift cluster Mass estimate 1; Scaling relations Mass estimate 2; Weak lensing The magnification bias The future

Clusters Clusters & Cosmology Cluster collapse; cosmology Cluster surveys X-ray cluster catalogues The XMM cluster survey [XCS] Detecting clusters Cluster classification Redshift estimates High redshift cluster Mass estimate 1; Scaling relations Mass estimate 2; Weak lensing The magnification bias The future

XMM Cluster Survey [XCS]XMM Cluster Survey [XCS]

The XCS: Archival pointings Serendipitous detections

170 sq. deg. Present

500 sq. deg. Total 0.1<z<2 Currently 1847 Expect ~ 2000

The XCS: Archival pointings Serendipitous detections

170 sq. deg. Present

500 sq. deg. Total 0.1<z<2 Currently 1847 Expect ~ 2000

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allXCS

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500XCS

Detecting clustersDetecting clusters

Color key Extended sources, Green ellipses Point sources, red circles Unsure, Pink circles

Color key Extended sources, Green ellipses Point sources, red circles Unsure, Pink circles

From simulations we can recover our selection function.

Extended sources Simulated clusters

Cluster classificationCluster classification

Cluster zoo SDSS optical images Centered on X-ray

ra,dec Optical & X-ray

overlays X-ray photon density

contours 610 XCS extended

sources 7 classification types 9+ classifications

Cluster zoo SDSS optical images Centered on X-ray

ra,dec Optical & X-ray

overlays X-ray photon density

contours 610 XCS extended

sources 7 classification types 9+ classifications

Cluster classificationCluster classification

Results: Gold sample High Z False detections Cuts improve sample

Results: Gold sample High Z False detections Cuts improve sample

Soft counts % Gold Clusters

% All Clusters

>0 18 55

>200 41 77

>500 54 81

Redshift estimatesRedshift estimatesEmpirically, see LRGs inhabit the central regions of clusters. Empirically, see LRGs inhabit the central regions of clusters.

SDSS LRGs•Spec and Photo redshifts•Good Agreement

Test on ROSAT 400 sq. deg•Spectroscopic redshifts

Look along line of sight of the cluster, encounter an clump of LRGs. Assign LRG redshift to cluster

Redshift estimatesRedshift estimates

Apply the LRG redshift estimate technique to the XCS

Apply the LRG redshift estimate technique to the XCS

193 free cluster redshifts

Redshift estimates Redshift estimates Dedicated XCS photometric follow up NOAO + XCS -> NXSDedicated XCS photometric follow up NOAO + XCS -> NXS

More than 300 redshifts

136 for

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500XCS

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z = 0.27 ± 0.02

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z = 0.53 ± 0.01

High redshift clusterHigh redshift cluster The most distant spectroscopically confirmed cluster of galaxies found to date. XMM-XCS J2215.9-1738 or J2215.

The most distant spectroscopically confirmed cluster of galaxies found to date. XMM-XCS J2215.9-1738 or J2215.

• 5 pointings of a z=2.215 quasar• Cluster redshift 1.45• Temp > 6KeV

Standford et al astro-ph/0606075Hilton et al astro-ph/0708.3258

High redshift clusterHigh redshift cluster The most distant spectroscopically confirmed cluster of galaxies found to date. XMM-XCS J2215.9-1738 or J2215.

The most distant spectroscopically confirmed cluster of galaxies found to date. XMM-XCS J2215.9-1738 or J2215.

• 5 pointings of a z=2.215 quasar• Cluster redshift 1.45• Temp > 6KeV•

Standford et al astro-ph/0606075Hilton et al astro-ph/0708.3258

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σ v = 620 ±120km /s

OverviewOverview Clusters Clusters & Cosmology Cluster collapse; cosmology Cluster surveys X-ray cluster catalogues The XMM Cluster Survey [XCS] Detecting clusters Cluster classification Redshift estimates High redshift cluster Mass estimates 1; Scaling relations Mass estimate 2; Weak lensing The magnification bias The future

Clusters Clusters & Cosmology Cluster collapse; cosmology Cluster surveys X-ray cluster catalogues The XMM Cluster Survey [XCS] Detecting clusters Cluster classification Redshift estimates High redshift cluster Mass estimates 1; Scaling relations Mass estimate 2; Weak lensing The magnification bias The future

Mass estimate 1: Scaling relationsMass estimate 1: Scaling relationsCombining optical [large numbers, no masses] and X-ray [small numbers, masses] cluster catalogues to obtain a mass proxy applicable to optically selected clusters.

Combining optical [large numbers, no masses] and X-ray [small numbers, masses] cluster catalogues to obtain a mass proxy applicable to optically selected clusters.

X-ray clusters • eBCs,BCS,R400d,XCS• Reprocessed equally• [Dai et al ‘06]

Optical Clusters• Mass estimates• Constrain cosmology

Empirical Relationship

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Lopt =1035−0.35+0.35

Mass0.7−0.21+0.22

Examine properties of X-ray clusters with a counter part in SDSS

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TX → Mass

Mass estimates 2: Weak lensingMass estimates 2: Weak lensing

The Sloan has enabled the creation of two massive optical catalogues:

The Sloan has enabled the creation of two massive optical catalogues:

We can follow Scranton et al ’05, and use a weak lensing mass measurement, called magnification bias.

MaxBCG clusters [Koester et al ’07]~13.10^30.1<z<0.3 volume limitedWell determined redshiftsNumber of galaxiesLack mass estimatesMember Galaxy luminosity

DR4 Quasars [Richards et al]~3.10^50.5<z<2.255-band SDSS magnitudes

The magnification bias The magnification bias

The QSO unlensed source density:

The QSO unlensed source density:

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n0(> f ) = a0 f−α ( f )

The magnification bias The magnification bias Lensing changes the measured source density, by stretching the solid angle

Lensing changes the measured source density, by stretching the solid angle

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n →n0

μ

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μ =μ(θ,Mass,zqso,zcluster )

The magnification bias The magnification bias

Lensing magnifies the source flux

Lensing magnifies the source flux

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f →f

μ

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μ =μ(θ,Mass,zqso,zcluster )

The magnification bias The magnification bias

• The sign of the correlation• The signal strength• The sign of the correlation• The signal strength

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wCQ = α −1( )b δμ.δ(θ + φ)

The cross correlation, is a function of bias, b, the weak lensing departure from unity, ,and the line of sight integrated density contrast,

Where alpha is the gradient of the QSO distribution, multiplied by 2.5There is a change of sign of€

∝δμ

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∝ α −1

Schnieder & Bartelmann astro-ph/9912508€

δμ

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δ

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α −1

The magnification bias, resultsThe magnification bias, resultsWe find [preliminary results]:We find [preliminary results]:

Expect a strong correlation Expect a weak anti-correlation

Stack similar clusters, expect the signal strength to increase with cluster mass.

The futureThe futureWeak Lensing SDSS DR6 QSO 1 million QSO’s Redo with full MaxBCG Check systematics

Weak Lensing SDSS DR6 QSO 1 million QSO’s Redo with full MaxBCG Check systematics

Mass estimatesCompare X-ray & weak lensing mass measurementsAssign MaxBCG clusters masses

CosmologyAssume LCDM constrain cosmological parametersConstrain modified gravity models [Schaefer & Koyama ‘07]