The LSST and Experimental Cosmology at KIPAC David L. Burke SLAC/KIPAC SLAC HEP Seminar October 31, 2006

Outline Experimental Cosmology Gravitational Lensing KIPAC Activities The Large Synoptic Survey Telescope

Elements of Cosmology Space and Time The Big Bang and inflation. Homogeneous, isotropic, expanding universe. Matter and Energy Particles and quantum interactions. Mass and General Relativity. What we see in the laboratory. What we see in the sky.

What We See in the Sky ~150Redshift z =

The Expanding Universe Hubble Isotropic linear distance-velocity relation,  “Hubble Parameter” H 0. Perlmutter/Reiss 1998 Non-linear distance-redshift relation,  Dark Energy and the Cosmological Constant  Z =021

Matter in the Universe Geller/Huchra 1989 Large Scale Structure Rubin/Ford 1980 Galaxy Rotation Curves  Dark Matter and Evolution of Structure The “Great Wall”

Cosmic Microwave Background Penzias/Wilson 1964Mather/Smoot 1992 Wilkison 2006 Best Fit  CDM Seeds fertilized by cold dark matter grow into large scale structure.  “  CDM Model”

Concordance and Discord Is the universe really flat? What is the dark matter? Is it just one thing? What is driving the acceleration of the universe? What is inflation? Can general relativity be reconciled with quantum mechanics?

Experimental Cosmology CMB and Baryon Oscillations – d A (z) and H(z). Supernovae – d L (z). Galaxies and clusters – d A (z), H(z), and C l (z). Gravitational lensing – d A (z) and C l (z).

Elements of General Relativity (Sean Carroll, SSI2005, ) [Geodesic Equation] [Einstein Equation] The metric g , that defines transformation of distances in coordinate space to the distances in physical space we can measure, must satisfy these equations. Homogeneous, isotropic, flat, expanding universe: g  = a(t) a(t) a(t) More generally: Curvature of space. “Size” of space relative to time.Gravitational potential (weak) d  2 = dt 2 – a 2 (t) · dx 2

 E = 1.74 arc-sec Newton, Einstein, and Eddington Soldner 1801 Einstein 1915 Eddington 1919  “between 1.59 and 1.86 arc-sec”

Propagation of Light Rays There can be several (or even an infinite number of) geodesics along which light travels from the source to the observer.  Displaced and distorted images.  Multiple images.  Time delays in appearances of images. Observables are sensitive to cosmic distances and to the structure of energy and matter (near) line-of-sight.

A complete Einstein ring. Strong Lensing Galaxy at z =1.7 multiply imaged by a cluster at z = 0.4. Multiply imaged quasar (with time delays).

Propagation of a Bundle of Light Central Ray  0 ξiξi ξjξj  ξ (  )  Bundle of rays each labeled by angle with respect to the central ray as they pass an observer at the origin.  Linear approximation, and  = 0 case, ξ ( ) = D ( )   D ( ) = d A ( )   angular diameter distance 2-dimensional vector

Weak Lensing Approximation If distances are large compared to region of significant gravitational potential , the deflection of a ray can be localized to a plane – the “Born” approximation. Unless the source, the lens, and the observer are tightly aligned (Schwarzschild radius), the deflection will be small, And the actual position of the source can be linearly related to the image position, (Einstein)

Distorted Image  Source ξiξi ξjξj Convergence and Shear “Convergence”  and “shear”  determine the magnification and shape (ellipticity) of the image. Distortion matrix with the co-moving coordinate along the geodesic, and a function of angular diameter distances. ( )

Simulation courtesy of S. Colombi (IAP, France). Weak Lensing of Distant Galaxies Sensitive to cosmological distances, large-scale structure of matter, and the nature of gravitation. Source galaxies are also lenses for other galaxies.

Observables and Survey Strategy Galaxies are not round!  g ~ 30% The cosmic signal is  1%. Must average a large number of source galaxies. Signal is the gradient of , with zero curl.  “ B-Mode” must be zero.

Ellipticity (Shear) Measurements 16 arc-sec 2000 Galaxies 200 Stars WHT Bacon, Refregier, and Ellis (2000)  i   i /2

Instrumental PSF and Tracking Mean ellipticity ~ 0.3%. Images of stars are used to determine smoothed corrections. Bacon, Refregier, and Ellis (2000)

Weak Lensing Results Discovery (2000 – 2003) 1 sq deg/survey 30,000 galaxies/survey CFHT Legacy Survey (2006) 20 sq deg (“Wide”) 1,600,000 galaxies “B-Mode” Requires Dark Energy (w 0 < -0.4 at 99.7% C.L.)

Shear-Shear Correlations and Tomography Maximize fraction of the sky covered, and reach z s ~ 3 to optimize sensitivity to dark energy. Two-point covariance computed as ensemble average over large fraction of the sky ξ 2 (  ) =. Fourier transform to get power spectrum C(l).  Tomography – spectra at differing z s. z s = 1  CDM with only linear structure growth. 0.2  22 1’

Experimental and Computational Cosmology at KIPAC Cosmic microwave background. (Church) First objects, formation of galaxies. (Abel, Wechsler) Clusters of galaxies and intergalactic medium. (Allen) Supernovae. (Romani) Gravitational lensing. (Allen, Burchat, Burke, Kahn)

Cosmic Microwave Background Temperature Polarization WMAP QUaD High resolution observations of CMB with QUaD at the South Pole. Also studies of the Sunyaev-Zeldovich effect in galaxy clusters in combination with X-ray cluster investigations.

Supernovae with SDSS II Fall a SNe SDSS 2.5m Hobby-Eberly 9.2m Taking data through Complete the magnitude-redshift distribution.

Formation of Galaxies and Clusters Observations, theory, and simulations. New techniques and exploiting best available data. Complementary constraints from different methods: eg direct distance measures, growth of structure and geometric. Allen et al. Rapetti et al.

Gravitational Lensing by Clusters Measurements of baryonic and dark matter in galaxy clusters from multi-wavelength observations (X-ray and gravitational lensing). Gravitational potentials of baryonic and dark matter in clusters. Separation of baryonic and dark matter in merging systems. Allen et al.Bradac et al.

Large Synoptic Survey Telescope (Burchat, Burke, Kahn, Schindler) 8.4m Primary-Tertiary Monolithic Mirror 3.5° Photometric Camera 3.4m Secondary Mirror

The LSST Mission Photometric survey of half the sky (  20,000 square degrees). Multi-epoch data set with return to each point on the sky approximately every 4 nights for up to 10 years. Prompt alerts (within 60 seconds of detection) to transients. Fully open source and data. Deliverables Archive 3 billion galaxies with photometric redshifts to z = 3. Detect 250,000 Type 1a supernovae per year (with photo-z < 0.8).

Cosmology with LSST o Weak lensing of galaxies to z = 3. Two and three-point shear correlations in linear and non-linear gravitational regimes. o Supernovae to z = 1. Lensed supernovae and measurement of time delays. o Galaxies and cluster number densities as function of z. Power spectra on very large scales k ~ h Mpc -1. o Baryon acoustic oscillations. Power spectra on scales k ~ h Mpc -1. Simultaneously in one data set.

LSST Site Cerro Pachón Gemini South and SOAR LSST Site

Telescope Optics Paul-Baker Three-Mirror Optics 8.4 meter primary aperture. 3.5° FOV with f/1.23 beam and 0.20” plate scale.

Camera and Focal Plane Array Filters and Shutter Focal Plane Array 3.2 Giga pixels ~ 2m Wavefront Sensors and Fast Guide Sensors “Raft” of nine 4kx4k CCDs. 0.65m Diameter

Aperture and Field of View Primary mirror diameter Field of view Keck Telescope 0.2 degrees 10 m 3.5 degrees LSST

Optical Throughput – Eténdue AΩ All facilities assumed operating100% in one survey

LSST Postage Stamp (10 -4 of Full LSST FOV) Exposure of 20 minutes on 8 m Subaru telescope. Point spread width 0.52 arc-sec (FWHM). Depth r < 26 AB. Field contains about 10 stars and 100 galaxies useful for analysis. 1 arc-minute LSST will see each point on the sky in each optical filter this well every 6-12 months.

Optical Filter Bands Transmission – atmosphere, telescope, and detector QE.

Photometric Measurement of Redshifts – “Photo-z’s” Galaxy Spectral Energy Density (SED) Moves right larger z.Moves left smaller z. “Balmer Break”

Photo-z Calibration Calibrate with 20,000 spectroscopic redshifts. Need to calibrate bias and width to 10% accuracy to reach desired precision Simulation of 6-band photo-z.  z  0.05 (1+z) Simulation photo-z calibration.  z  0.03 (1+z)

Shear Power Spectra Tomography Linear regimeNon-linear regime ΛCDM 11 0.2  22

Precision on Dark Energy Parameters Measurements have different systematic limits. Combination is significantly better than any individual measurement. DETF Goal

Weighing Neutrinos Free streaming of massive neutrinos suppresses large scale structure within the horizon distance at the time the neutrinos freeze out. The suppression depends on the sum of the neutrino masses,   m  Hu, Eisenstein, and Tegmark 1998  m = 0.2 h = 0.65 PP

Present Status and Forecast Present atmospheric value:  m 32 2 = 1.9 – 3.0  eV 2 (90%CL), or Σm > eV. Forecast for LSST (contours):  Σm   eV (statistical). Hannastad, Tu, and Wong (2006) Goobar, Hannestad, Mörtsell, Tu (2006)  CDM Present Limits 1432

Project Milestones and Schedule 2006 Site Selection Construction Proposals (NSF and DOE) Complete Engineering and Design Long-Lead Procurements Construction 2013First Light and Commissioning