3D dark matter map

z=0.5

z=0.7

z=1

z=0.3Right ascension

Dec

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z=0

Mapping dark matter withweak gravitational lensing

Richard MasseyCalTech

zobserver=0

zgalaxy≈1

zlens≈0.3–0.5

Observe light from distant galaxies, behind any structure we’re interested in.

Gravitational Lensing

• Translation• Magnification• Shear• Flexion/curvature

Gravitational lenses are sensitive to any mass along the line of sight and, like glass lenses, are most effective when it is half way between the source and the observer.

NASA, ESA, and M. J. Jee (JHU)

CL 0024+17

Shapes of galaxies are random so, in the absence of lensing, averaging ~100 would produce a circle. Galaxies on adjacent lines of sight are coherently distorted.

zobserver=0

zgalaxy≈1

zlens≈0.3–0.5

Observe light from distant galaxies, behind any structure we’re interested in.

Weak Gravitational Lensing

Gravitational lenses are sensitive to any mass along the line of sight and, like glass lenses, are most effective when it is half way between the source and the observer.

• Translation• Magnification• Shear• Flexion/curvature

• Largest ever survey with HST• 1.6 square degrees in IF814W band• Depth IF814W<26.6 (at 5)• 2 million galaxies, zmedian=1.2• Small, diffraction-limited PSF• ~80 resolved galaxies/arcmin2

• Follow-up from radio to x-rays• Photo-zs from 17 optical/IR bands

Dark matter simulation at z=0.5Andrey Kravtsov and Anatoly Klypin

(National Center for Supercomputer Applications)

Hubble Space Telescope COSMOS surveyGravitational lensing convergence projected mass

B-mode check for residual systematicsR. Massey et al. (Nature 2007)

Redshift tomography

z=0.3

z=0.5

z=0.7

years ago

Statistical analysis of 3D mass distributionR. Massey et al. (ApJ 2007), J. Lesgourgues et al. (JCAP submitted)

z=0.7

Shear-shear correlation function

z=0.5

z=0.3

Cosmological parameter constraints

WMAP

SDSSLy forest

COSMOS3D weak lensing

VHS Ly forest

Redshift-distance relationJames Taylor et al. (in prep)

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Redshift

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Redshift

Well-know shape as a function of angular diameter distancefrom simple lens geometry

Distribution of visible and dark matter

Comparison with baryons

Weak lensingmass contours(HST)

Extended x-rayemission (XMM-Newton)

Galaxy numberdensity(Subaru/CFHT)

Galaxy stellarmass(Subaru/CFHT)

R. Massey et al. (Nature 2007)

Mass vs light tomography (z~0.3)~19Mpc 19Mpc

R. Massey et al. (Nature 2007)

Mass vs light tomography (z~0.5)~26Mpc 26Mpc

R. Massey et al. (Nature 2007)

Mass vs light tomography (z~0.7)~31Mpc 31Mpc

R. Massey et al. (Nature 2007)

“Bullet” cluster 1E0657-56

1.5’

Doug Clowe, Marusa Bradac et al. (Astrophysical Journal 2006)

The largest particle accelerator in the universe

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

“Bullet” cluster 1E0657-56

1.5’

Doug Clowe, Marusa Bradac et al. (Astrophysical Journal 2006)

Radial mass profile

Face-on bulletJames Jee et al. (Astrophysical Journal 2007))

Two clustersalong line of sight

Face-on bullet

QuickTime™ and aMotion JPEG A decompressor

are needed to see this picture.

NASA, ESA and M. J. Jee (Johns Hopkins University)

Conclusions & future prospects

Remarkably fast progress since first statistical detections of cosmic shear in 2000. Gravitational lensing is now a major tool in cosmology.

We can now compare the large-scale distribution of baryons to that ofmass. In general, baryonic structures are built inside a dark matter scaffold. Discrepancies on small scales reveal the different(e.g. non-interacting) properties of dark matter.

Statistical analyses of the mass distribution constrain cosmological parameters, trace the growth of structure, and measure the expansion history of the universe.

Could not have been done from the ground.Wide-field imaging from space is essential,backed up by multicolour photometry: theuntimely failure of ACS is heartbreaking.Hubble provides a unique proof of concept for ambitious, dedicatedmissions in the future.

Fin

Lensing sensitivity with redshift

Resolved background galaxies

Redshift

Foreground lensing sensitivity

Can anything be done from the ground?

Ground vs space (mass maps)

Using 71 galaxies per arcmin2

SPACE GROUND

R. Massey et al. (Nature 2007), M. Kasliwal et al. (Proc. AAS 2007)

Ground vs space (B-mode/noise in mass maps)R. Massey et al. (Nature 2007), M. Kasliwal et al. (Proc. AAS 2007)

SPACE GROUND

Using 71 galaxies per arcmin2

Ground vs space (cluster detection over z range)M. Kasliwal et al. (Proc. AAS 2007)

SPACE

GROUND

SPACE

GROUND

Redshift 0.73 Redshift 0.93

Redshift 0.22Redshift 0.35

SPACEGROUND SPACE

GROUND

Mass vs x-raysA. Finoguenov (in prep)

Charge Transfer (in)Efficiency

STIS image, Paul Bristow

Trailing during CCD readout creates a spurious, coherent ellipticity.Affects photometry, astrometry and morphology of faint galaxies.

Effect of CTE trailing on the mass map

PSF variation

HST “breathing” affects both size & ellipticity of PSFEffective focus changes by• 3m per orbit• 12m in ~days

J. Rhodes (ApJ 2007)J. Jee (ApJ 2005)

PSF variationJ. Rhodes (ApJ 2007)

Manufacture realistic images, containing a known shear signal.

Animations show 0-10% shear in 1% steps (real signal is ~2%).

Real imageSimulated image

R. Massey et al. (MNRAS 2004)

Shear TEsting Programme (STEP) simulations

Shear TEsting Programme (STEP) resultsC. Heymans et al. (MNRAS 2006)R. Massey et al. (MNRAS 2007)

Mass vs light 2D projectionR. Massey (Nature 2007)

20’

Growth of dark matter structureR. Massey et al. (ApJ 2007)

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Radial mass profile of cluster CL 0024+17

PSCz galaxy density < 150 Mpc/hW. Sutherland et al. (1991)

COSMOS mass density,R. Massey et al. (Nature 2007)

Lensing is coming of age