Cosmic scaffolding and the growth of structure

Richard Massey (CalTech)

with

Jason Rhodes (JPL), David Bacon (Edinburgh), Joel Bergé (Saclay), Richard Ellis (CalTech), Alexis Finoguenov (Garching), Catherine Heymans

(UBC),J-P Kneib (Marseilles), Alexie Leauthaud

(Marseilles), Alexandre Refregier (Saclay), Nick Scoville (CalTech), Elisabetta Semboloni (Bonn),

James Taylor (Waterloo), Ludovic Van Waerbeke (UBC) and the 70+ COSMOS team

Cosmic scaffolding andthe growth of structure

Core HST data in COSMOS field

http://irsa.ipac.caltech.edu/Missions/cosmos.html

Largest ever HST survey• 577 contiguous ACS pointings• 1.6 square degrees in IF814W band (VSDSS at z=1)• Depth IF814W<26.6 (at 5)• 2 million galaxies• ~80 resolved galaxies/arcmin2

N. Scoville et al. (ApJ 2007)

Multicolour data in COSMOS fieldP. Capak et al. (ApJ 2007), B. Mobasher et al. (ApJ 2007)

z/(1+z)= 0.05 , 0.15

Lensing sensitivity with redshift

Resolved background galaxies

Redshift

Foreground lensing sensitivity

1/r2

Weak lensing analysisConvergence projected mass • Real data (no Bhuvnesh

here!)• RRG shear measurement• Calibrated on STEP3-like sims

• PSF model varies with focus• Parametric CTE correction

Multiscale wavelet reconstruction methodJ.-L. Starck, S. Pires & A. Refregier (A&A 2006)

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

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)

Dealing with photometric redshift degeneraciesP. Capak et al. (ApJ 2007), B. Mobasher et al. (ApJ 2007)

Faint galaxies

X

XFaint galaxies

photo-z0 1 2 3 4

probability

z=0.3

z=0.5

z=0.7

Redshift tomography (palaeocosmology)

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)

z=0.5

z=0.7

z=1

z=0.3Right ascension

Dec

linat

ion

z=0

Bacon & Taylor 3D reconstruction

3D dark matter map animation

ESA/Hubble (M. Kornmesser & L. L. Christensen)

QuickTime™ and a decompressor

are needed to see this picture.

3D cosmic shear

z=0.7

Shear-shear correlation function +()

z=0.5

z=0.3

R. Massey et al. (Astrophysical Journal 2007)

Full 3D analysis

Traditional2D analysis

Cosmological parameter constraintsR. Massey et al. (Astrophysical Journal 2007)

Growth of structureR. Massey et al. (Astrophysical Journal 2007)

Fraction of mass on different scales

ConclusionsLargest ever HST survey - ideal proof of concept for future, dedicated missions in space. Various problems encountered, but all HST-specific and none generic to space. Know what needs to be done better!

Comparison of the large-scale distribution of baryons to that of mass,which could not have been done from the ground. In general, masstraces light - consistent with a scenario where baryonicstructures are built inside a preformed dark matter scaffold. Discrepancies on small scales reveal the different nature of dark matter.

Statistical analysis of the mass distribution constrains cosmological parameters, traces the growthof structure (and measures the expansion history of the universe). Multicolour follow-up, particularly in near IR, is essential! 3D analysis yields ~3ximprovement.

Fin

PSF variation

HST’s thermal “breathing” affects both size and 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)

Charge Transfer (in)EfficiencySTIS image, courtesy Paul Bristow

Trailing during CCD readout creates a spurious, coherent ellipticity.

Affects photometry, astrometry and morphology of faint galaxies.

CCD readout register

Effect of CTE trailing on the mass map

• 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)

Compare to simulations

Gravitational lensing convergence projected mass

Lensing sensitivity with redshift

Resolved background galaxies

Redshift

Foreground lensing sensitivity

1/r2