Transcript Mapping the Heavens: Probing Cosmology with Large Sky Surveys Josh Frieman Fermilab Colloquium, January 18, 2006

Mapping the Heavens:
Probing Cosmology with
Large Sky Surveys
Josh Frieman
Fermilab Colloquium, January 18, 2006
2MASS Infrared Sky Survey
Large-scale Structure: patterns in the distribution of galaxies
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)
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
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
SDSS
CfA
Dark Energy and Dark Matter
Probe Dark Matter
and Dark Energy by
surveying the
Large-scale Structure
of the Universe
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
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.
Cold Dark Matter
Models
Power Spectrum
of the Mass Density
k  
 d 3 x  e ik  x
P ~ kn
mh =0.2
x 

P ~ k–3
 k1  k2  
2  Pk1 3 k1  k2 
3
Power spectrum
measurements
probe cosmological
parameters
mh =0.5
keq ~ mh
Linear
Non-linear
h/Mpc
Two Kinds of Galaxy Surveys
Photometric: imaging  2D sky maps: positions, brightnesses
(and colors if more than one band)
Spectroscopic: redshifts  distances (via Hubble’s Law):
3D maps
~106 galaxies
UK Schmidt Imaging Survey (photographic plates)
Two Degree Field (2dF) Survey at the AAT
Galaxy
Spectroscopic
Targets
selected
from the
APM imaging
Survey
400-fibre spectrograph with robotic positioner
221283 galaxies
completed 2002
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
Builders of the
SDSS
SDSS 2.5 meter Telescope
Apache Point Observatory
Southern New Mexico
SDSS Imaging Camera
Top to bottom:
g’
z’
u’
i’
r’
Drift Scan Mode
Perseus cluster
Spectroscopic Plates for Redshift Survey
640 fibers per plate
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
Color: intrinsic
Galaxy Luminosity
Galaxy Clustering as a function of Galaxy Luminosity
bright
faint
Zehavi, etal
Tegmark, etal
Based on sample of ~200,000 galaxies
Correct
For
Luminosity
Bias
Vertical
Shift:
Constant
Bias
ngal L, x 
ngal L
 bL
x

SDSS Galaxy Power Spectrum
CDM Model:
mh2=0.155
bh2=0.024
ns=1
Tegmark etal
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
Combined Power Spectrum
Tegmark et al.
Constrain Neutrino Mass
Dodelson
95%
Constraints
Neutrino
masses
m < 1.7 eV
Priors:
spatially flat
w=–1
ns = const
r=0
Tegmark etal
mh2
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
“Halo Occupation” Model for Bias
Assume:
1.
2.
All galaxies live in dark matter halos.
Galaxy content of a halo is statistically independent of the
halo’s larger scale environment. Depends only on mass.
The bias of a certain galaxy class (type, luminosity, etc) is fully defined by:
• The probability distribution P(N|M) that a dark halo of mass M contains N galaxies
<N>M
P(N|<N>)
• The relation between the galaxy and dark matter spatial distribution within halos
• The relation between the galaxy and dark matter velocity distribution within halos
Halo Occupation Distribution
Two-point Correlations in the Halo Model
Large scales: All pairs come from separate halos:
Small scales: All pairs from same halo:
Halo Model
fit to
Clustering of
Bright
SDSS
Galaxies
Evidence for
Scale-dependent
Bias
galaxies
2-halo
1-halo
N~M
Zehavi etal
M1
mass
Halo Occupation Modeling
Zheng, Zehavi, etal
Cosmological
Constraints
SDSS
wp constraints
marginalized
over Halo
Model
parameters
Abazajian, etal
Acoustic Oscillations in the CMB
Temperature map of
the cosmic microwave
background 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.
Acoustic Oscillations in the CMB
WMAP (Bennett et al)
Sound Waves in the Early Universe
Ionized
After recombination:
 Universe is neutral.
 Photons can travel freely past the
baryons.
 Phase of oscillation at trec affects
late-time amplitude.
Recombination
z ~ 1000
~400,000 years
Time
Neutral
Today
Big Bang
Before recombination:
 Universe is ionized.
 Photons provide enormous pressure
and restoring force.
 Perturbations oscillate as acoustic
waves.
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
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.
Large-scale Correlations of
SDSS Luminous Red Galaxies
Redshiftspace
Correlation
Function
Acoustic series in
P(k) becomes a
single peak in (r)
Pure CDM model
has no peak
Warning:
Correlated
Error Bars
Baryon
Acoustic
Oscillations
Seen in
Large-scale
Structure
Eisenstein, etal
Model Comparison
Fixed bh2=0.024
ns=0.98, flat
CDM with baryons is a good fit: c2 = 16.1 with 17 dof.
Pure CDM rejected at Dc2 = 11.7
Equality scale depends
on (mh2)-1.
Acoustic scale depends
on (mh2)-0.25.
mh2 = 0.12
mh2 = 0.13
mh2 = 0.14
bh2 = 0.00
Gravitational Lensing
See the same effects that occur in more familiar optical
circumstances: magnification and distortion (shear)
Apparent position 2
True position 2
Apparent Position 1
True Position 1
Objects farther from
the line of sight are
distorted less.
Observer
Gravitational “lens”
“Looking into” the lens:
extended objects are
tangentially distorted...
Lensing conserves surface brightness: bigger image  magnified
Gravitational Lensing
Cluster of Galaxies
`giant arcs’ are galaxies behind the cluster, gravitationally lensed by it
Mapping
the Dark
Matter
in a Cluster
of Galaxies
via Weak
Gravitational
Lensing
Data from
Blanco 4-meter
at CTIO
Joffre, etal
Weak Lensing of Faint Galaxies: distortion of shapes
Background
Source
shape
Weak Lensing of Faint Galaxies: distortion of shapes
Foreground
galaxy
Background
Source
shape
Note: the effect has been greatly exaggerated here
Lensing of real (elliptically shaped) galaxies
Foreground
galaxy
Must co-add signal from a
large number of foreground galaxies
Background
Source
shape
December 14, 1999
SDSS
GalaxyGalaxy
Lensing
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
Lensing Cluster
Source
Image
Tangential shear
Statistical Weak Lensing by Galaxy Clusters
Mean
Tangential
Shear
Profile
in Optical
Richness
(Ngal) Bins
to 30 h-1Mpc
Sheldon,
Johnston, etal
Preliminary
David Johnston
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
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
On-going SN surveys
(200)
Future Surveys:
PanSTARRS, DES, JDEM, LSST
(2000) (2000)
(105)
Supernova
Hubble
Diagram
CFHT
Supernova
Legacy Survey
1st year: ~90 SNe Ia
Astier etal 05
Redshift desert: SDSS
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
Assuming w = –1
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 >1 surveys
• Database of Type II and rare SN light-curves
SDSS II SN Team
Fermilab: J. Adelman-McCarthy, F. DeJongh, G. Miknaitis,
J. Marriner, C. Stoughton, D. Tucker, D. Lamenti (SF State)
J. Frieman
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
SDSS
SN 2005 ff
Before
After
z = 0.07, confirmed at WHT
Preliminary gri light curve and fit
Composite gri
SN 2005 gb
images
Before
After
z = 0.086, confirmed at ARC 3.5m
Preliminary gri light curve and fit from low-z templates
Follow-up
Spectra from
Subaru 8m
Confirmed Ia’s
SDSS II:
139
spectroscopically
confirmed
Type Ia
Supernovae
from the
Fall 2005
Season
The Dark Energy Survey
• Study Dark Energy using
4 complementary* techniques:
Blanco 4-meter at CTIO
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
*geometric+growth: test Dark Energy vs. Gravity
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
The DES Instrument
3556 mm





62 CCD camera
2kx4k CCDs, 0.26”/pixel
17 second readout time
4 filters: g,r,i,z
5 optical element corrector
•
•
•
Camera Scroll
one aspheric surface
Shutter Filters
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.
1575 mm
Optical
Lenses

Cluster Redshift Distribution
and Dark Energy
Constraints:
Raising w at fixed DE:
 decreases volume surveyed
 decreases growth rate of
density perturbations
dN(z)
dV

n z
dzd dzd
dV
2
 H cz  d A2 1 z
dA 
dzd
d A 1 z is proper distance
Dark Energy
Equation of state
dz'
 0 E (z')
z
H z  H o E(z) is the Hubble parameter
Volume effect
Growth effect
Mohr
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.
Weak lensing: shear and mass
Jain
Galaxy Angular Baryon Oscillations
Angular Power Spectrum for 0.9 < z < 1
Hu
Use the galaxy angular power spectrum within
redshift shells, concentrating only on the
portion with 50 < l < 300 to avoid non-linearity
and bias complexity
Expected photo-z errors small
compared to cosmic variance
DES Supernovae
•
Repeat observations of 40 deg2 ,
10% of survey time
.02(1+z)/1.8 mag error floor in Dz=0.1 bins assumed
• ~1900 well-measured riz SN Ia
lightcurves, 0.25 < z < 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-z’s (needed for LSST)
•
In-situ photometric response measurements
SN constraints `orthogonal’
to the other methods
Huterer
The Large Synoptic
Survey Telescope
Time-Domain Astronomy
survey visible sky every few
nights
Weak Lensing
Cluster Counts
Galaxy Clustering
….
Proposed Joint
Dark Energy
Mission to
observe
~3000 SNe Ia
out to z ~ 1.7,
plus a
Weak Lensing
survey