Mapping the Heavens:

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Mapping the Heavens Probing Cosmology with Large
Sky Surveys
Josh Frieman Fermilab Colloquium, January 18,
2006
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2MASS Infrared Sky Survey
Large-scale Structure patterns in the
distribution of galaxies
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Superclusters and Large-scale Structure
Filaments, Walls, and Voids of Galaxies
Center for Astrophysics Redshift Survey (1986)
300 Million Light-years
You Are Here
Watermelon Slice 6 degrees thick containing
1060 galaxies position of each galaxy
represented by a single dot Radial coordinate is
redshift (much easier to measure than distance)
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Superclusters and Large-scale Structure
Filaments, Walls, and Voids of Galaxies
Center for Astrophysics Redshift Survey (1986)
300 Million Light-years
You Are Here
Watermelon Slice 6 degrees thick containing
1060 galaxies position of each galaxy
represented by a single dot
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Superclusters and Large-scale Structure
Filaments, Walls, and Voids of Galaxies
Coma Cluster of Galaxies Finger of God
300 Million Light-years
You Are Here
Watermelon Slice 6 degrees thick containing
1060 galaxies position of each galaxy
represented by a single dot
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SDSS
CfA
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Dark Energy and Dark Matter

Probe Dark Matter and Dark Energy by surveying
the Large-scale Structure of the Universe
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Evolution of Structure in a Universe with Dark
Matter and Dark Energy The Cosmic
Web Galaxies and Clusters form in sheets and
filaments Robustness of the paradigm
recommends its use as a cosmological probe
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The Structure Formation Cookbook
1. Initial Conditions A Theory for the Origin of
Density Perturbations in the Early
Universe Primordial Inflation initial
spectrum of density perturbations 2. Cooking
with Gravity Growing Perturbations to Form
Structure Set the Oven to Cold (or Hot
or Warm) Dark Matter Season with a few
Baryons and add Dark Energy 3. Let Cool for 13
Billion years Turn Gas into Stars
4. Tweak (1)
and (2) until it tastes like the observed
Universe.

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Cold Dark Matter Models Power Spectrum of the
Mass Density
P kn
?mh 0.2
P k3
?mh 0.5
keq ?mh
Power spectrum measurements probe
cosmological parameters
Non-linear
Linear
h/Mpc
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Two Kinds of Galaxy Surveys
Photometric imaging ? 2D sky maps positions,
brightnesses
(and colors if more than one
band) Spectroscopic redshifts ? distances
(via Hubbles Law)
3D maps
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106 galaxies
UK Schmidt Imaging Survey (photographic plates)
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Two Degree Field (2dF) Survey at the AAT
Galaxy Spectroscopic Targets selected from the
APM imaging Survey
400-fibre spectrograph with robotic positioner
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221283 galaxies completed 2002
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SLOAN DIGITAL SKY SURVEY (2000-2008)
GOAL MAP THE UNIVERSE IN 3 DIMENSIONS
OVER A LARGE VOLUME

• Imaging Survey 100 million galaxies stars

• Redshift Survey 1,000,000 galaxies and 100,000
  quasars
• covering 1/4 of the sky

http//www.sdss.org
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Builders of the SDSS
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SDSS 2.5 meter Telescope
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Apache Point Observatory Southern New Mexico
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SDSS Imaging Camera Top to bottom g
z u i r Drift Scan Mode
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Perseus cluster
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Spectroscopic Plates for Redshift Survey
640 fibers per plate
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Galaxy Clustering varies with Galaxy Type How
are each of them related to the underlying
Dark Matter distribution? Caveat for
inference of Cosmological Parameters from LSS
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Color intrinsic Galaxy Luminosity
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Galaxy Clustering as a function of Galaxy
Luminosity
bright
faint
Zehavi, etal
Tegmark, etal
Based on sample of 200,000 galaxies
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Correct For Luminosity Bias Vertical Shift Const
ant Bias
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SDSS Galaxy Power Spectrum
?CDM Model Wmh20.155 Wbh20.024 ns1
Tegmark etal
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Cosmic Microwave Background Wilkinson Microwave

Anisotropy Probe (WMAP)
SDSS galaxies today
Universe at 400,000 years Combine these
two to constrain Cosmology Dark Matter and
Dark Energy
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Combined Power Spectrum
Tegmark et al.
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Constrain Neutrino Mass
Dodelson
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95 Constraints Neutrino masses ?m? lt 1.7
eV Priors spatially flat w 1 ns const r
0 Tegmark etal
?mh2
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Dark Energy constraints ?(w) 0.15, w lt 0.76
(95) with priors
95 constraints

assuming w 1
assuming w constant
Tegmark, etal
Key priors scale-free spectrum, no gravity
waves, massless neutrinos, const. bias
Additional prior flat Universe
from CMBLSSSNe no single dataset constrains w
better than 30
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Precision Cosmology with Large-scale Structure?

• Requires a more nuanced treatment of
• Bias as a function of galaxy type
• Redshift distortions
• Non-linear evolution of fluctuations
• As well as very large sample sizes
• Jointly constrain cosmological and bias
  parameters

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Halo Occupation Distribution
Halo Occupation Model for Bias

• All galaxies live in dark matter halos.
• Galaxy content of a halo is statistically
  independent of the
• halos larger scale environment. Depends
  only on mass.

Assume
The bias of a certain galaxy class (type,
luminosity, etc) is fully defined by

• The probability distribution P(NM) that a dark
  halo of mass M contains N galaxies
• ltNgtM
  P(NltNgt)
• The relation between the galaxy and dark matter
  spatial distribution within halos
• The relation between the galaxy and dark matter
  velocity distribution within halos

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Two-point Correlations in the Halo Model
Large scales All pairs come from separate halos
Small scales All pairs from same halo
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Halo Model fit to Clustering of Bright
SDSS Galaxies Evidence for Scale-dependent Bias
Zehavi etal
galaxies
2-halo
mass
1-halo
NM?
M1
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Halo Occupation Modeling
Zheng, Zehavi, etal
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Cosmological Constraints SDSS wp
constraints marginalized over Halo Model parameter
s Abazajian, etal
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Acoustic Oscillations in the CMB
Temperature map of the cosmic microwave backgroun
d radiation

• Although there are fluctuations on all scales,
  there is a characteristic angular scale, 1
  degree on the sky, set by the distance sound
  waves in the photon-baryon fluid can travel just
  before recombination.

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Acoustic Oscillations in the CMB
WMAP (Bennett et al)
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Sound Waves in the Early Universe

• Before recombination
• Universe is ionized.
• Photons provide enormous pressure and restoring
  force.
• Perturbations oscillate as acoustic waves.

• After recombination
• Universe is neutral.
• Photons can travel freely past the baryons.
• Phase of oscillation at trec affects late-time
  amplitude.

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Sound Waves

• Each initial overdensity (in dark matter gas)
  is an overpressure that launches a spherical
  sound wave.
• This wave travels outwards at 57 of the speed
  of light.
• Pressure-providing photons decouple at
  recombination. CMB travels to us from these
  spheres.
• Sound speed plummets. Wave stalls at a radius of
  150 Mpc.
• Overdensity in shell (gas) and in the original
  center (DM) both seed the formation of galaxies.
  Preferred separation of 150 Mpc.

Eisenstein
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A Statistical Signal

• The Universe is a super-position of these shells.
• The shell is weaker than displayed.
• Hence, you do not expect to see bullseyes in the
  galaxy distribution.
• Instead, we get a 1 bump in the correlation
  function.

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Large-scale Correlations of SDSS Luminous Red
Galaxies
Redshift- space Correlation Function
Baryon Acoustic Oscillations Seen
in Large-scale Structure
Eisenstein, etal
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Model Comparison
Fixed Wbh20.024 ns0.98, flat
CDM with baryons is a good fit c2 16.1 with 17
dof. Pure CDM
rejected at Dc2 11.7
Wbh2 0.00
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Gravitational Lensing
See the same effects that occur in more familiar
optical circumstances magnification and
distortion (shear)
Objects farther from the line of sight are
distorted less.
Lensing conserves surface brightness bigger
image ?? magnified
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Gravitational Lensing
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Cluster of Galaxies
giant arcs are galaxies behind the cluster,
gravitationally lensed by it
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Mapping the Dark Matter in a Cluster of
Galaxies via Weak Gravitational Lensing Data
from Blanco 4-meter at CTIO Joffre, etal
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Weak Lensing of Faint Galaxies distortion of
shapes
Background Source shape
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Weak Lensing of Faint Galaxies distortion of
shapes
Foreground galaxy
Background Source shape
Note the effect has been greatly exaggerated here
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Lensing of real (elliptically shaped) galaxies
Foreground galaxy
Background Source shape
Must co-add signal from a large number of
foreground galaxies
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December 14, 1999
SDSS Galaxy- Galaxy Lensing
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Toward an Understanding of Bias SDSS Galaxy-mass
vs. Galaxy-galaxy Correlations weak lensing 8
million sources 100,000 lenses Sheldon,
Johnston, etal
?gm
?gg
Bias
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Lensing Cluster
Source
Image
Tangential shear
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Statistical Weak Lensing by Galaxy Clusters
Mean Tangential Shear Profile in
Optical Richness (Ngal) Bins to 30
h-1Mpc Sheldon, Johnston, etal
Preliminary
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David Johnston
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Lensing Calibrates Richness vs. Cluster Virial
Mass
Calibrate Mass-observable relation in future
Cluster surveys
SDSS preliminary (low-z)
or any other observable
Johnston, Sheldon, etal
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SDSS and SDSS II

• SDSS I April 2000-June 2005
• SDSS II July 2005-2008
• Legacy Survey (complete extragalactic
  survey)
• SEGUE (low-latitude survey of Milky
  Way)
• Supernova Survey Sept-Nov. 2005-7

American Museum of Natural History, Astrophysical
Institute Potsdam, University of Basel,
Cambridge University , Case Western Reserve
University, University of Chicago, Drexel
University, Fermi National Accelerator
Laboratory, Institute for Advanced Study, Japan
Participation Group, Johns Hopkins University,
Joint Institute for Nuclear Astrophysics, Kavli
Institute for Particle Astrophysics and
Cosmology Stanford/SLAC, Korean Scientist Group,
LAMOST, Los Alamos National Laboratory,
Max-Planck-Institute for Astronomy/Heidelberg,
Max-Planck-Institute for Astrophysics/Garching,
New Mexico State University, Ohio State
University, University of Pittsburgh, University
of Portsmouth, Princeton University, US Naval
Observatory, University of Washington
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On-going SN surveys
(200)
Future Surveys PanSTARRS, DES, JDEM, LSST

(2000) (2000) (105)
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Supernova Hubble Diagram CFHT
Supernova Legacy Survey 1st year 90 SNe
Ia Astier etal 05
Redshift desert SDSS
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Assuming w 1
Cosmological Constraints CFHT Supernova
Legacy Survey (SNLS) Baryon Oscillations from
SDSS (BAO) Astier etal 05 Eisenstein etal 04 See
also Riess etal 04, Knop etal 03, Tonry
etal 03
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SDSS Supernova Science Goals

• Obtain 200 high-quality SNe in the redshift
  desert
• repeat multi-band data over 250 square
  degrees
• Probe Dark Energy in z regime less sensitive to
  evolution than deeper surveys
• Study SN Ia systematics (critical for SN
  cosmology) with high photometric accuracy
• Search for additional parameters to reduce Ia
  dispersion
• Determine SN/SF rates/properties vs. z,
  environment
• Rest-frame u-band templates for z gt1 surveys
• Database of Type II and rare SN light-curves

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SDSS II SN Team
Fermilab J. Adelman-McCarthy, F. DeJongh, G.
Miknaitis, J. Marriner, C.
Stoughton, D. Tucker, D. Lamenti (SF State) U.
Chicago B. Dilday, R. Kessler, M. SubbaRao U.
Washington A. Becker, C. Hogan Portsmouth R.
Nichol, M. Smith, B. Bassett NMSU J. Holtzman,
T. Gueth APO SDSS 3.5m observing
specialists Japan M. Doi, N. Yasuda, N.
Takanashi, K. Konishi Stanford R. Romani, M.
Sako, J. Kaplan Ohio State D. DePoy, J. L.
Prieto, J. Marshall Space Telescope A. Riess, H.
Lampeitl JINA P.
Garnavich External Collaborators M. Richmond
(RIT), E. Elson (SAAO),
K. van den Heyden (SAAO), D. Cinabro
(Wayne State) graduate student
undergraduate
J. Frieman
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SDSS SN 2005 ff
Before
After
z 0.07, confirmed at WHT
Preliminary gri light curve and fit
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SN 2005 gb
Composite gri images
Before
After
z 0.086, confirmed at ARC 3.5m
Preliminary gri light curve and fit from low-z
templates
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Follow-up Spectra from Subaru 8m Confirmed Ias
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SDSS II 139 spectroscopically confirmed Type
Ia Supernovae from the Fall 2005 Season
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The Dark Energy Survey
Blanco 4-meter at CTIO

• Study Dark Energy using
• 4 complementary techniques
• Cluster counts clustering
• Weak lensing
• Galaxy angular clustering
• SNe Ia distances
• Two multiband surveys
• 5000 deg2 g, r, i, z
• 40 deg2 repeat (SNe)
• Build new 3 deg2 camera
• Construction 2005-2009
• Survey 2009-2014 (525 nights)
• Response to NOAO AO

in systematics in cosmological parameter
degeneracies geometricgrowth test Dark Energy
vs. Gravity
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The DES Collaboration
Fermilab J. Annis, H. T. Diehl, S. Dodelson, J.
Estrada, B. Flaugher, J. Frieman, S. Kent, H.
Lin, K. W. Merritt, J. Peoples, V. Scarpine, A.
Stebbins, C. Stoughton, D. Tucker, W.
Wester University of Illinois at
Urbana-Champaign C. Beldica, R. Brunner, I.
Karliner, J. Mohr, R. Plante, P. Ricker, M.
Selen, J. Thaler University of Chicago J.
Carlstrom, S. Dodelson, J. Frieman, M. Gladders,
W. Hu, S. Kent, E. Sheldon, R. Wechsler
Lawrence Berkeley National Lab G. Aldering, N.
Roe, C. Bebek, M. Levi, S. Perlmutter
NOAO/CTIO T. Abbott, C. Miller, C. Smith, N.
Suntzeff, A. Walker Institut d'Estudis Espacials
de Catalunya F. Castander, P. Fosalba, E.
Gaztañaga, J. Miralda-Escude Institut de Fisica
d'Altes Energies E. Fernández, M.
Martínez University College London O. Lahav, P.
Doel, M. Barlow, S. Bridle, D. Brooks, S. Viti,
S. Worswick, J. Weller University of Cambridge
G. Efstathiou, R. McMahon, W. Sutherland
University of Edinburgh J. Peacock University
of Portsmouth R. Nichol University of Michigan
R. Bernstein, B. Bigelow, M. Campbell, A.
Evrard, D. Gerdes, T. McKay, M. Schubnell, G.
Tarle, M. Tecchio Ciemat Madrid C. Mana, M.
Molla, E. Sanchez UAM Madrid J.
Garcia-Bellido
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The DES Instrument

• 62 CCD camera
• 2kx4k CCDs, 0.26/pixel
• 17 second readout time
• 4 filters g,r,i,z
• 5 optical element corrector
• one aspheric surface
• largest element is 1m
• UCL Optical Sciences Lab beginning design and
  engineering work

Instrument total cost 22.4M, includes 35
contingency Equipment 11.4 M Labor 7
M Overhead 4 M
Optics and CCDs are the major cost and schedule
drivers Optics Total 2M 1M cont. CCD Total
2M 1M cont.
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Cluster Redshift Distribution and Dark Energy
Constraints

• Raising w at fixed WDE
• ? decreases volume surveyed

? decreases growth rate of density
perturbations
Dark Energy Equation of state
Mohr
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Background sources
Dark matter halos
Observer

• Statistical measure of shear pattern, 1
  distortion.
• Radial distances, r(z), depends on geometry of
  Universe.
• Dark Matter pattern growth depends on
  cosmological parameters.

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Weak lensing shear and mass
Jain
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Galaxy Angular Baryon Oscillations
Hu
Use the galaxy angular power spectrum within
redshift shells, concentrating only on the
portion with 50 lt l lt 300 to avoid non-linearity
and bias complexity
Expected photo-z errors small compared to cosmic
variance
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DES Supernovae
.02(1z)/1.8 mag error floor in ?z0.1 bins
assumed

• Repeat observations of 40 deg2 ,
• 10 of survey time
• 1900 well-measured riz SN Ia
• lightcurves, 0.25 lt z lt 0.75
• Larger sample, improved z-band response compared
  to ESSENCE, SNLS
• address issues they raise
• Combination of spectroscopic (25?)
• and photometric SN redshifts
• Develop test color typing and SN
• photo-zs (needed for LSST)
• In-situ photometric response measurements

SN constraints orthogonal to the other methods
Huterer
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The Large Synoptic Survey Telescope

• Time-Domain Astronomy
• survey visible sky every few
• nights
• Weak Lensing
• Cluster Counts
• Galaxy Clustering
• .

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Proposed Joint Dark Energy Mission to observe
3000 SNe Ia out to z 1.7, plus a Weak
Lensing survey