Post on 01-Jan-2016
description
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)
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
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
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.
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)
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
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
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