Determining cosmological parameters with current

observational data

TPCSF

Li Hong

2008.12.10

The cosmological observations play a crucial role in understanding universe !

CMB 、 LSS and SN

Complementary, GRB and WL also make remarkable progress !

•Recent years Cosmology became • more and more accurate

outline

• The global fitting analysis • The constraints on cosmological parameter

s with the latest observational data• Constraints on EOS including GRBs • Simulations for LAMOST• Summary

Global fitting procedure

• Parameterization of EOS: • Perturbation included G.-B. Zhao, et al., PRD 72 123515 (2005)• Method : modified CosmoMC

Calculated at ShangHai Supercomputer Center (SSC)

• Data : CMB+LSS+SNe

• Cosmological parameters:

)1()( 10 awwaw

))sin(ln()( 210 awwwaw

For simplicity, usually consider flat Universe

Quintessece

Quintom A

Quintom B

Phantom

Current constraint on the equation of state of dark energy

WMAP5 resultE. Komatsu et al., arXiv:0803.0547

Xia, Li, Zhao, Zhang, in preparation

Status: 1) Cosmological constant fits data well;2) Dynamical model not ruled out;3) Best fit value of equation of state: slightly w across -1 Quintom model

Difference:

Data: SN (SNLS+ESSENCE+Riess et al.)vs SN (307,Kowalski et al., arXiv:0804.4142)

Method: WMAP distance prior vs Full CMB data.However, results similar (Li et al., arXiv: 0805.1118)

Arxiv: 0805.1118, Accepted by APJ Lett.

For the published version :

Take into account the recent weak lensing data

Global analysis of the cosmological parameters including GRBs

• Results from the global analysis with WMAP3+LSS+SNe(Riess 182 samples)+GRBs (Schaefer 69 sample)

• 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, Phys.Lett.B658:95-100,2008

WMAP3+LSS+SN

WMAP3+LSS+SN+GRB

)1/(* zzwww a0

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

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

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 !

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., APJ 680, 92 (2008)

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!

• www.lamost.org

z~ 0.2

n~ galaxies710

H.Feldman, et al. Astrophys.J. 426, 23 (1994)

Firstly we take the bias factor: b=1Then we let b free, see the following

Simulations for LAMOST

Simulated power spectrum

1

70 , 7.0 , 3.0 0

s

m

n

H

CDM

Fiducial model:

About other simulations

• Planck: we assume the isotropic noise with variance and a symmetric gaussian beam of 7 arcminutes full-width half-maximum : A. Lewis, Phys.RevD71,083008(2005)

(See the paper by arXiv: 0708.1111, J.-Q. Xia, H. Li et al.)

• SNLS: ~ 500 SN Ia

241032/ KNN EEl

TTl

Constraint on cosmological parameters with LAMOST

Constraints on EoS of Dark Energy

Constraint on absolute neutrino mass

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 Planck and LAMOST will improve the constraints

H. Li, J.-Q. Xia, Zu-Hui Fan and X. Zhang, JCAP 10 (2008) 046