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Future observational prospects Future observational prospects for dark energy for dark energy Roberto Trotta Oxford Astrophysics & Royal Astronomical Society
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Future observational prospectsFuture observational prospectsfor dark energy for dark energy
Roberto TrottaOxford Astrophysics
& Royal Astronomical Society
R. Trotta - [email protected]
Investigating dark energyInvestigating dark energy
The equation of state parameter w(z) = p/– w = -1– w = const -1– w(z) – or perhaps another theory of gravity
Theoretical explanations must be guided by observational constraints:
weff ~ -1 § 0.2 for z < 1
TODAY
Seljak et al 2005Jarvis et a 2005
R. Trotta - [email protected]
Observational techniquesObservational techniques
Weak gravitational lensing
Baryonic acoustic oscillations
Integrated Sachs-Wolfe effect
SNe luminosity distance (fluctuations?)
Cluster abundance
Challenging control of systematics
Less accurate, but systematics free
Limited by cosmic variance
SNe variability, evolution
Do we understand clusters? Calibration
Nu
mb
er
of
ass
um
pti
on
s
R. Trotta - [email protected]
Weak gravitational lensingWeak gravitational lensing
Based on well-understood physics– Independent of mass-to-light relation– Probes geometry & growth of structures– Potential to achieve percent accuracy on w– Limited to z < 1
Systematic errors control– Image quality (0.1 to 1% distortions)– Gravitational-intrinsic correlations– Photo-z accuracy (tomography) – Non-linear effects
Strategies– Large (104-105) spectroscopic training sets– B-modes quantify the success of the correction – Use of radial information, cross-correlations between redshift bins– Combination of tomography/reconstruction with geometric test,
checks for consistency
R. Trotta - [email protected]
Baryonic acoustic oscillationsBaryonic acoustic oscillations
A clean probe of geometry – Measures the angular diameter
distance (transverse) and expansion rate (radial)
– No known systematic effect can erase/mimick it
– Based on well-known physical processes
– Extends our window to z ~ 3– In-built consistency check– Independent probe, curvature test,
distinguish modifications of GR
radia
l )
H(z
)
transverse ! DA(z)
Requirements– Large and deep spectroscopic survey (GWFMOS)– Photo-z’s are insufficient
Disadvantage– Lower statistical accuracy than weak lensing
Dark energy discovery spaceDark energy discovery space
Observational techniquesGrowth of structures
Clusters Weak lensing
Standard rulers
Acoustic oscillations SNe type IaTom
ogra
ph
y
3D
reco
nst
ruct
ion
geom
etr
ic t
est
+ P
lanck
CM
B
+ P
lanck
CM
B
+ P
lanck
CM
B
2015
transv
ers
e (
2D
)
+ P
lanck
CM
B
Photometryz = 1
transv
ers
e +
radia
l (3
D)
+ P
lanck
CM
B +
SD
SS
+ S
Ne
Spectroscopyz=1 and z = 3A
ccura
cy o
n w
20%
10%
5%
1-2%
20%
10%
5%
1-2%
systematics impact
+ S
Z +
WL
calib
rati
on
+ P
lanck
CM
B
+ P
lanck
CM
B
20092015
R. Trotta - [email protected]
ProposalsProposals
Dark Energy Survey, darkCAM– visible survey cameras, 4-5 bands– 5,000 – 10,000 sq deg to z » 1
Pan-STARRS– US Air Force, 4 telescopes planned– 3,000 sq deg in 5 bands
Spectrographs– VIRUS, 200 sq deg, z » 3– AAOmega, 500 to 1,000 sq deg– GWFMOS (HyperSuprime), z ~ 1 and z ~ 3
(Almost) everything you can think of – LSST, SKA (> 2015)
GW
FMO
Sdark
CA
MD
ES
> 1 billion USD worth of proposals until 2015
Present and upcoming surveysPresent and upcoming surveys
2006 2009 2013 2014 2015
Imagin
g s
urv
eys
Sp
ect
rosc
opy
SNe
WL
BAOSZ
BAO
LSST ?20’000 deg2
out to z » 3
CFHT-LS 700 SNe DES 5’000 deg2, 4% on wPan-STARRS, full system deployed in 2009?
VST – KIDS 1700 deg2
DES 5’000 deg2, 1-2% on w
darkCAM, 1-2% on wCFHT-LS 170 deg2
Pan-STARRS, full system deployed in 2009?
GWFMOS 2’000 deg2 @ z » 1 300 deg2 @ z » 3
AAOmega 1’000 & 500 deg2 ?
VIRUS ?200 deg2 @ z » 3
Pan-STARRS, full system deployed in 2009?
DES 5’000 deg2, 5-20% on w
darkCAM, 5-20% on wSPT
R. Trotta - [email protected]
““Trust me, I’m a Bayesian!”Trust me, I’m a Bayesian!”
Bayes factor B01
RT (2005)
Present
Mis
matc
h w
ith
pre
dic
tion
0
Evidence in favour of w=-1 compared to -1/3 < w < -1
= 0.1 not worth mentioning= 0.01 moderate= 0.002strong
Future
R. Trotta - [email protected]
Closing remarksClosing remarks
Preparing for the unexpected– What will be the most interesting questions in 2010?– Dark energy could surprise us again: maximise the discovery potential
Developping know-how– Indispensable tools on the road to even larger surveys
Making the most of the data– Statistical tools for optimal parameter inference– Model selection approach, surveys optimization
Plenty of other science!– Next generation of surveys will provide extremely high quality data for
numerous astronomical and astrophysical studies
