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Cosmic scaffolding and the growth of structure 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 Core HST data in COSMOS field N. Scoville et al. (ApJ 2007) 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 http://irsa.ipac.caltech.edu/Missions/cosmos.html Multicolour data in COSMOS field P. Capak et al. (ApJ 2007), B. Mobasher et al. (ApJ 2007) z/(1+z)= 0.05 , 0.15 Lensing sensitivity with redshift 1/r2 Resolved background galaxies Foreground lensing sensitivity Redshift Weak lensing analysis Convergence 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 method J.-L. Starck, S. Pires & A. Refregier (A&A 2006) B-mode check for residual systematics R. Massey et al. (Nature 2007) Comparison with baryons Weak lensing mass contours (HST) Extended x-ray emission (XMM-Newton) Galaxy number density (Subaru/CFHT) Galaxy stellar mass (Subaru/CFHT) R. Massey et al. (Nature 2007) Dealing with photometric redshift degeneracies P. Capak et al. (ApJ 2007), B. Mobasher et al. (ApJ 2007) Faint galaxies probability X 2 photo-z 3 4 Faint galaxies 1 X 0 Redshift tomography (palaeocosmology) z=0.7 z=0.5 z=0.3 Mass vs light tomography (z~0.3) R. Massey et al. (Nature 2007) ~19Mpc 19Mpc Mass vs light tomography (z~0.5) R. Massey et al. (Nature 2007) ~26Mpc 26Mpc Mass vs light tomography (z~0.7) R. Massey et al. (Nature 2007) ~31Mpc 31Mpc Bacon & Taylor 3D reconstruction z=1 z=0.7 z=0.5 z=0.3 z=0 3D dark matter map animation QuickTime™ and a decompressor are needed to see this picture. ESA/Hubble (M. Kornmesser & L. L. Christensen) 3D cosmic shear Shear-shear correlation function +() R. Massey et al. (Astrophysical Journal 2007) z=0.7 z=0.5 z=0.3 Cosmological parameter constraints R. Massey et al. (Astrophysical Journal 2007) Full 3D analysis Traditional 2D analysis Growth of structure Fraction of mass on different scales R. Massey et al. (Astrophysical Journal 2007) Conclusions Largest 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, mass traces light - consistent with a scenario where baryonic structures 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 growth of structure (and measures the expansion history of the universe). Multicolour follow-up, particularly in near IR, is essential! 3D analysis yields ~3x improvement. Fin PSF variation J. Rhodes (ApJ 2007), J. Jee (ApJ 2005) HST’s thermal “breathing” affects both size and ellipticity of PSF Effective focus changes by • 3m per orbit • 12m in ~days PSF variation J. Rhodes (ApJ 2007) Charge Transfer (in)Efficiency STIS image, courtesy Paul Bristow CCD readout register 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 Compare to simulations Gravitational lensing convergence projected mass • 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=0.5 Andrey Kravtsov and Anatoly Klypin (National Center for Supercomputer Applications) Lensing sensitivity with redshift 1/r2 Resolved background galaxies Foreground lensing sensitivity Redshift
