probing for dynamics of dark energy with latest cosmological data

Probing for dynamics of dark energy

with latest cosmological dataHong Li

Department of AstronomyPeking University

In collaboration withJunqing Xia, Gongbo Zhao, Zuihui Fan a

nd Xinmin Zhang

outline

• Brief review on DE • Global anlysis on the determination of

EOS of DE with WMAP3+LSS+SNe• Constraints on EOS including GRBs • Summary

Dark Energy: Negative pressure:)3(

3

4/ p

Gaa

0a 3/1/ 03 pwp

* Smoothly distributed, (almost ) not clusteringCandidates:I Cosmological constant (or vacuum Energy)

g

GT

8

1/ pw eV10~m

)102(8

3-

43

eVG

p

12010~/ obth cosmological constant problem!II Dynamical Field: Quintessence, K-essence, Phantom, Quintom etc

)(2

1QVQQL

VQpVQ QQ 22

2

1,

2

1

11 Qw

The equation of state (EOS) w: a parameter characterizing DE

The model independent data analysis need the parameterization of w:

zwww 10

)1/(

)1(

10

10

zzww

awww

●

●

* Vacuum : w=-1

* Quintessence:

* Phantom:

* K-essence: or but cannot across -1 * Quintom: crossing w=-1 ……………..

Global fitting procedure

• Parameterization of EOS:

• Perturbation included

G.-B. Zhao, et al., PRD 72 123515 (2005)

• Method : modified CosmoMC

• Data : WMAP+LSS+SN

• Cosmological parameters:

)1()( 10 awwaw

assuming flat universe,

For non-flat, see later

))sin(ln()( 210 awwwaw

Constrains on dark energy with SN Ia (Riess) + SDSS + WMAP-1

Observing dark energy dynamics with supernova, microwave background and galaxy clustering Jun-Qing Xia, Gong-Bo Zhao, Bo Feng, Hong Li and Xinmin Zhang Phys.Rev.D73, 063521, 2006

The importance of DE perturbation!

2007.6.5 IHEP 博士论文答辩

Constraints on EOS with WMAP3Relative error: ~9%

Relative error > 50% !!

* Emphasizing the importance of the perturbation of DE* A constant EOS considered by the WMAP group

Global fitting with SN Ia, SDSS and WMAP3

• The standard ΛCDM model is still a good fit to the current data

• Quintom is mildly favored

410.0176.0305.0178.00 146.1

w

410.0176.0305.0178.00 146.1

w

802.0622.0996.1652.01 6.0

w

Probing dynamics of DE with supernova, galaxy clustering and the three-year Wilkinson Microwave Anisotropy Probe (WMAP) observations G.-B. Zhao, J.-Q. Xia, B. Feng and X. Zhang, astro-ph/0603621

)1/(*1 zzwww 0

Global fitting with

• Parameterization of EOS: • Perturbation included• Method : MCMC• Data : WMAP+SDSS+SN• Cosmological

parameters:

K

)1()( 10 awwaw

The flat Universe is a good approximation, for within 2σC.L. 06.0K

Global analysis of the cosmological parameters including GRBs

• Results from the global analysis with WMAP3+LSS

+SNe(Riess 182 samples)+GRBs (Schaefer 69 sa

mple)

• New method for solution of the circulation problem

the 69 modulus published by Schaefer (in astro-ph/0612285)

Bias with only GRB

Need global analysis

Hong Li, M. su, Z.H. Fan, Z.G. Dai and X.Zhang, astro-ph/0612060, to appear in Phys. Lett. B

WMAP3+LSS+SN

WMAP3+LSS+SN+GRB

)1/(* zzwww a0

The relevant papers on study with GRBs:E.L.Wright astro-ph/0701584

F.Y. Wang, Z. G. Dai and Z. H. Zhu, astro-ph/0706.0938

They use the shift paramater R, BAO from LSS, and so on…..

Problems:

• The circulation problem : Due to the lack of the low-redshift GRBs, the experiential correlation is obtained from the high-redshift GRBs with input cosmology !

• Using shift parameter : the loss of the full information of CMB data in the global fitting

CMBz

k

k

m

zE

dzR

0 )'(

'sinn

020.067.1 ),,,,(:)6

023.070.1 ),,,,,,(:)5

038.077.1 ),,,,,,(:)4

032.066.1 ),,,,,,(:)3

030.074.1 ),,,,,,(:)2

022.070.1 ),,,,,(:)1

022

022

022

022

022

022

RAHhh

RAnHhh

RmAnHhh

RrAnHhh

RAnHhh

RAnHhh

scb

ksscb

sscb

sscb

ssscb

sscb

S_r is the fluence of the r-ray; t_j is the Break time; n is the circumburst particle Density; eta_r is the fraction of the kineticEnergy that translate to the r-rays;E_peak is the peak energy of the spectrum

What is the circulation problem?

• Due to the lack of the low-redshift GRBs, the experiential correlations are obtained from the high-redshift GRBs with input cosmology which we intend to constrain, it lead to the circulation problem!

From the observation, we can get: S_r, t_j, n, eta_r, E_peak

With a fire ball GRB model:

Ghirlanda et al.

UsuallyInput a cosmology

Get A & C

A new method for overcoming the circulation problem for GRBs in global analysis

ApeakcEE

We integrate them out in order to get the constraint on the cosmological parameter:

We let A and C free:

We can avoid the circulation problem ! And method can apply to the other correlations.

EEpeak Correlation as an example:We takeHong Li et al., to appear

For flat universe !

With free ! K

For flat universe !

The constraints on A and C related with the correlation:

i. e., in the literature C is set to [0.89, 1.05]; A is set to 1.5One can find that, this will lead to the bias to the final constraints on The cosmological parameters!

SUMMARY Our results on determining EOS of DE with MCM

C from WMAP+SDSS+SN(+GRBS) ; Cosmological constant fits the current data well

at 2 sigma; Quintom is mildly favored ; The Future observation like SNAP and Planck will improve the constant

J.-Q. Xia, H. Li, G.-B. Zhao and X. Zhang, astro-ph/0708.1111