DARK ENERGY

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DARK ENERGY
PHENOMENOLOGY PRESENT/FUTURE OBSERVATIONS
RICHARD BATTYE
JODRELL BANK OBSERVATORY SCHOOL OF PHYSICS AND
ASTRONOMY UNIVERSITY OF MANCHESTER
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PLAN OF TALK

• DARK ENERGY PHENOMENOLOGY
• CURRENT OBSERVATIONAL STATUS
• FUTURE COSMOLOGICAL TESTS - REVIEW
• CLUSTER SURVEYS WITH THE SZ EFFECT

EFECTS OF DARK ENERGY MODELS THERE IS MORE TO
LIFE THAN w !LINEAR PERTURBATIONS
WORK WITH ADAM MOSS
CMB ALONE SNe ALONE CMB 2dF SNe
EFFECT OF PERTURBATIONS
WEAK LENSING (TALK BY ANDY TAYLOR) NUMBER
COUNTSP(k,z) - BARYONIC OSCILLATIONS X-CORRELATIO
N BETWEEN CMB AND LSS
WORK WITH JOCHENWELLER
AN EXAMPLE OF NUMBER COUNTS
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BASIC OBSERVATIONAL SITUATION
SNe Ia

2dF/SDSS
CMB
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DARK ENERGY PHENOMENOLOGY
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DARK ENERGY

• PRESSURE TO DENSITY RATIO
• w-1 COSMOLOGICAL CONSTANT
• SCALAR FIELDS QUINTESSENCE
• TOPOLOGICAL DEFECT LATTICES
• MODIFICATIONS TO GRAVITY ?
• SUPER-HORIZON PERTURBATIONS !

ASSUME FLAT UNIVERSE
NB POSSIBLE NON-MINIMAL COUPLING TO GRAVITY
EASY TO MODEL GIVEN A LAGRANGIAN
MODELLED AS A RELATIVISTIC SOLID ie A FLUID WITH
RIGIDITY
COSMIC STRINGS w-1/3DOMAIN WALLS
w-2/3
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TWO CLASSES OF TESTS
GEOMETRICAL
GROWTH OF STRUCTURE
ONLY DEPENDS ON w !
GROWTH DEPENDS ON w AND ALSO ON THE PROPERTIES
OF THE DARK ENERGY
ANGULAR DIAMETER DISTANCE
LINEAR REGIME
LUMINOSITYDISTANCE
NON-LINEAR REGIME
(i) MASS FUNCTION (ii) SPHERICAL COLLAPSE
() OFTEN GEOMETRIC DEPENDENCE AS WELL
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EXAMPLES OF GEOMETRICAL TESTS
TYPE Ia SUPERNOVAE
PEAK IN CMB POWER SPECTRUM
degeneracy
degeneracy (lgt100)
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GROWTH OF DENSITY PERTURBATIONS
N-BODY SIMULATIONS (VIRGO COLLABORATION)
NEWTONIAN THEORY
GROWTH HALTS AT L DOMINATION
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INTEGRATED SACHS-WOLFE EFFECT
PHOTON TRAJECTORY
DF
FOR STATIONARY POTENTIALS
GRAVITATIONAL POTENTIALS DECAY ONCE DARK ENERGY
DOMINATES
THIS MODIFIES CMB POWER SPECTRUM AT LOW lBREAKS
GEOMETRICAL DEGENERACY - BUT MODEL DEP
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DIFFERENT MODELS FOR DE
EQUATIONS OF MOTION FOR A GENERAL FLUID
NON-ADIABATIC (SCALAR FIELD)
(Hu Weller Lewis Bean Dore)
ADIABATIC (SOLID)
(Bucher Spergel Battye, Bucher Spergel)
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LOW l CMB POWER SPECTRUM
W-1/3
W-2/3
W-4/3
LCDM
SCALAR FIELD
SOLID
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PRESENT OBSERVATIONAL STATUS
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CMB DATA ALONE
SCALAR FIELD DARK ENERGY
ISOTROPIC SOLID DARK ENERGY
THIS ANALYSIS FAVOURS w-1/3 COSMIC STRING MODELS
BEST FIT MODELS
NO PERTURBATIONS IN DE
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SUPERNOVA DATA
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CMB 2dF SNe
SCALAR FIELD DARK ENERGY
NO PERTURBATIONS
ISOTROPIC SOLID DARK ENERGY
MESSAGE TAKE CARE WITH w !
NB CMB ALMOST BURNT OUT IN TERMS OF DE, BUT
2000 SNe CAN BE JDEM AND OTHERS
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FUTUREOBSERVATIONALTESTS
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NUMBER COUNTS
SKY COVERAGE
COMOVING NUMBER DENSITY - EVOLUTION
SELECTION FUNCTION FLUX LIMITED
EXAMPLES RADIO SOURCES GRAVITATIONAL
LENSES CLUSTERS (X-RAY,
SZ, REDSHIFT SURVEYS)
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NUMBER COUNTS CLUSTERS
2
2
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DEPENDENCE ON COSMOLOGY
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NUMBER COUNTS IMPORTANT FEATURES
SURVEY YIELD CALCULABLE TOTAL NUMBER OF
OBJECTS LARGE REDSHIFT DEPENDENCE NOISE
RATHER THAN CONFUSION DOMINATED CONTROL OF
SYSTEMATICS
ACCURATE CORRELATION BETWEEN MASS AND PROXY (EG
FLUX)
POISSON ERRORS
SEPARATE OPTICAL SURVEY?
NEED TO AVOID CONTAMINATION
IS THE MASS PROXY UNBIASED ?
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BARYONIC OSCILLATIONS
(EISENSTEIN 2003)
z500
z20
z100
BARYONS
CDM
z0
OSCILLATIONS TRANSFERRED FROM BARYONS TO CDM
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DEPENDENCE ON PARAMETERS
w-1
w-1/3
w-2/3

• PLOTTED RELATIVE TO ZERO BARYONS
• BREAKS GEOMETRICAL DEGENERACY
• NON-LINEAR SCALE SMALLER AT HIGH z
• REQUIRES UNDERSTANDING OF BIAS

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BARYONIC OSCILLATIONS STATUS
(EISENSTEIN et al astro-ph 2005)
EFFECT DETECTED IN (i) SDSS LUMINOUS RED GALAXY
SURVEY
(ii) 2dF (Cole et al 2005)
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X-CORRELATION LSS CMB
(CRITTENDEN TUROK 1996)
ISW EFFECT
LARGE-SCALE STRUCTURE
0 for matter dominated universes
selection function
bias
CROSS-CORRELATE
WHERE
SENSITIVE TO ISW AND HENCE PERTURBATIONS IN DE
COULD BE USED TO DISTINGUISH DE MODELS
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X-CORRELATION STATUS

• X-ray Background 2.4-2.8s(Boughn
  Crittenden)
• NVSS (Radio) 1.8-2.3s(Boughn Crittenden)
• 2MASS (Infra-red) 2.5s(Afshordi, Loh
  Strauss)
• SDSS (Optical) 90-95 confidence (Scranton et
  al)

LCDM prediction
W 1
m
XRB CROSS CORRELATION
(Boughn Crittenden, Nature 2004)
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FUTURE REDSHIFT SURVEYS

• LARGE NUMBER OF OBJECTS
• LARGE COSMOLOGICAL VOLUME
• ACCURATE REDSHIFTS
• BIAS - WHAT IF IS SCALE DEPENDENT?
• PLANNED SURVEYS - AN INCOMPLETE LIST

POISSON ERRORS ARE DOMINANT SOURCE OF ERRORS
WIDE AREA DEEP SURVEYS
PHOTOMETRIC V SPECTRSCOPIC
Dark Energy Survey OPT 108 gal to z1 PHOTO-z
2009 DarkCam on VISTA OPT/IR
" PHOTO-z 2009KAOS OPT out to
z3.5! SPEC-z 2012 LSST OPT PHOTO-z
2012SKA RADIO 109 gal to
z1.5 SPEC-z 2015
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CLUSTER SURVEYSUSING THESZ EFFECT
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THERMAL SUNYAEV-ZELDOVICH EFFECT
DT INDEPENDENT OF z
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QUANTIFYING THE THERMAL SZ EFFECT
x f/56.4GHz
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TARGETED OBSERVATIONS
(Lancaster et al 2004)
RYLE TELESCOPE
VERY SMALL ARRAY
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1ST GENERATION INSTRUMENTS 50deg
2
- INTERFEROMETERS
AMI
SZA
10x3.7m ANTENNAE CAMBRIDGE n15GHz Tsys25K,
Dn6GHz RYLE TELESCOPE
8x3.5m ANTENNAE OWENS VALLEY, CA n30GHz
90GHz LINK WITH CARMA
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2ND GENERATION INSTRUMENTS -LARGE AREA OR VERY
DEEP SURVEYS
GROUND BASED SPT, ACT, APEX-SZ

• MULTI-ELEMENT FOCAL PLANE ARRAYS
• HIGH RESOLUTION 1', 100-5000 deg
• BOLOMETERS 150GHz
• TOTAL POWER -NEED A DRY SITE
• 1000-10000 CLUSTERS

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SPACE MISSIONS PLANCK

• MULTI-FREQUENCY 30GHz-850GHz
• LOW RESOLUTION 5'-10'
• POWERFUL REJECTION OF SYSTEMATICS
• ALL-SKY
• 5000-10000 NEARBY CLUSTERS

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INPUT PHYSICS SIMPLE MODEL
CORE RADIUS
SPHERICAL AND VIRIALIZED
SPHERICAL COLLAPSE
ISOTHERMAL
VIRIALRADIUS
GAS PROFILE
DISTRIBUTION IN M z
NUMERICAL SIMULATIONS
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COMPUTING THE SELECTION FUNCTION
8'
1'
4'
16'
2'
MAXIMAL
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COSMOLOGICAL DEPENDENCE
DIFFERENCE BETWEEN L AND w-0.80.3z FOR 1 sq.
deg
AT LEAST 750 sq deg NEEDED
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SIMULATED DATA
SPT
PLANCK
AMI/SZA
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SIMULATED CONSTRAINTS
FIDUCIAL MODEL w-0.80.3z
CENTRAL CONTOUR CORRESPONDS TO SPT
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COMPLEMENTARITY TO SNe Ia
SZ
SNe
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MASS-TEMPERATURE RELATION
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CONCLUSIONS

• DARK ENERGY APPEARS TO EXIST
• GOOD MICROSCOPIC MODELS SCARCE
• PHENOMOLOGICAL DESCRIPTION REQUIRED
• IN PRINCIPLE MANY WAYS TO TEST IT
• MANY SYSTEMATIC ISSUES TO BE ADDRESSED
• VARIATION IN w DIFFICULT
• DARK ENERGY EXPERIMENTS COST 10 MILLION
  //EUROS