Dynamical Dark Energy: Future constraints from cosmic complementarity and weak lensing tomography a

1
Dynamical Dark Energy Future constraints from
cosmic complementarity and weak lensing
tomography (a critical discussion)

• Mustapha Ishak
• Princeton University(M. Ishak and D. Spergel
  2004)
• (Work supported by NASA ATP grant and NSERC
  Fellowship)
• (A. Upadhye, M. Ishak and P. Steinhardt, 2004)

2
Motivation

• Look for clues on how to address and try to solve
  the dark energy problems
• Among problems associated with dark energy
• What is it? A cosmological constant? Or a
  dynamical component? Or neither (cosmic
  acceleration due to modified gravity)?
• Why is the value measured from cosmology so small
  compared to QFT calculations?
• Why did it become dominant during the present
  epoch? (timing problem)

3
Parameterizing Dark EnergyThe equation of state
(EOS)

• The equation of state two levels of difficulty
• A constant EOS with w only
• A dynamical component with w(z)

4
Probing the dark energy density(less model
dependent)

• Density as a continuous interpolated function
  (see Wang Freese 2004)
• 2 dimensionless density amplitude parameters ei
  ?de(zi)/ ?de(0)

5
Constraints on w0 w1 from currently available
data
6
Constraints on w0 w1 from currently available
data
7
Current constraints a summary

• Current data seems to favor a cosmological
  constant when a constant EOS is assumed
• Not possible to constrain dynamical models
  conclusively using currently available data
• In general, the central values w0lt-1 and w1gt0
• Recently, central values closer to a cosmological
  constant but we will see with the WMAP-2 analysis
  

8
How much better are we going to do in the
near/far future?

• A powerful trio SNWLCMB
• breaks various degeneracies between various
  cosmological parameters

9
Methods and analyses I

• Study 1 (Upadhye, Ishak and Steinhardt, 2004)
• Monte-Carlo simulations of SN (2200), WL
  (fsky0.7, n56 gal/arcmin2) and WMAP 8 year
  data.
• chi2 minimization, used vanilla model (w0, w1,
  zs)
• No strong priors assumed
• Applied the analysis to currently available data
  then to simulated future data

10
Methods and analyses II

• Study 2 (Ishak and Spergel, 2004)
• Used 2200 SN
• WL surveys with and without tomography
• WMAP-8, PLANK, ACTWMAP-8
• Used Fisher formalism (results are consistent
  with previous study for the WMAP-8 case)
• 10 cosmological parameters 3 systematic
  parameters considered (we added T/S, running, WL
  calibration parameters)
• 2 EOS parameterizations and 1 density
  parameterization
• 2 WL surveys ground-based like survey with 2
  bin tomography space-based like deep survey
  with 10 bin tomography

11
Summaryof ourresults(Study I) and
otherstudyresults
12
First conclusions

• The constraints we obtained without tomography
  and the ones published from other studies are not
  enough to rule out dynamical dark energy models
• The remaining uncertainty is roughly 0.10 at
  the one sigma level
• We require errors of 0.02 by comparison with
  the case of WMAP spatial curvature Ototal1.02
  0.02

13
Plot ICosmiccomplementarityCMB,SNeIa,and
WL
14
Table II weak lensing adds a factor of two
improvement to PlanckSN0.8, but still not
enough
15
Table III same but for the second
parameterization
16
10 bin tomography could make the necessary
improvement
17
Plot IIWL tomography.Constraints on the
EOSparameters
18
Discussion surveys

• The desirable level of precision (0.02 say, on
  all the DE parameters) seems possible from
  PlanckSN1.5WLT10 (very large fraction of
  the sky, multiple bin tomography)
• Results suggest that more ambitious and more
  sophisticated weak lensing surveys than what has
  been proposed are required (perhaps currently
  proposed experiments need to be enhanced)

19
Discussion systematic effects

• Some have been included in the analysis (for SN
  magnitude uncertainty, WL calibration, and source
  redshift distribution)
• But more need to be done intrinsic alignments,
  non-linear matter power spectrum calculation,
• These need to be well understood and tightly
  controlled in order to achieve the targeted level
  of precision

20
What is needed?

• More ambitious and sophisticated weak lensing
  surveys with very large fraction of the sky and
  many bin tomography.
• So, is this the way to go?

21
Conclusions

• Although there are some worries about
  systematics, our study suggests that
  PlanckSN1.5 ambitious weak lensing
  tomography (very large fractions of the sky and
  many redshift bins) can add KEY improvements to
  the dark energy parameter constraints (0.02)
• Using less ambitious surveys, we will be able to
  distinguish between some competing models
  (quintessence trackers, SUGRA models) but we will
  not be able to exclude all dynamical dark energy
  models
• Also, one should keep in mind that even in the
  case that (0.02) will be achieved in the far
  future, finding w0-1 and w10 will not solve the
  cosmological constant problems but confirm them.
• Therefore, in addition to current plans, other
  types of TESTS or measurements seem necessary to
  constrain decisively the true nature of dark
  energy.
• Testing the nature of dark energy beyond the
  equation of state or the density parameters may
  be the way to go Weak lensing is a promising
  tool for such tests (as it probes the expansion
  history the growth factor of LSS)