Observational Constraints on Dark Energy Zhu ZongHong Dept

Observational Constraints on Dark Energy Zhu, Zong-Hong Dept. of Astron. , Beijing Normal University, Beijing 100875, China zhuzh@bnu. edu. cn the 2 nd Sino-French Workshop

Breakthrough of 1998: the Winner ASTRONOMY: Cosmic Motion Revealed 10/31/2020 the 2 nd Sino-French Workshop 2

Breakthrough of 2003: the Winner Illuminating the Dark Universe 10/31/2020 the 2 nd Sino-French Workshop 3

How to accelerate the Universe? • General Relativity: 3 P 0 PDE < 0 ! 10/31/2020 the 2 nd Sino-French Workshop 4

Cosmological constant problem Fine tuning 10/31/2020 the 2 nd Sino-French Workshop 5

Cosmological constant problem log r Coincidence radiation (~1/a 4) matter (~1/a 3) cosmological constant (~constant) log a imagination dominated 10/31/2020 radiation dominated matter dominated Lambda dominated the 2 nd Sino-French Workshop 6

Beyond Einstein: 3 question marks What powered the Big Bang? What happans at the edge of a black hole? What is dark energy? 10/31/2020 the 2 nd Sino-French Workshop 7

A NNSFC Project: study on cosmic dark energy 1. 2. 3. 4. Beijing Normal University (Z. -H. Zhu group) Institute of High Energy Physics, CAS (X. Zhang group) National Astronomical Observatories, CAS (X. Chen group) Peking University (Z. Fan group) 10/31/2020 the 2 nd Sino-French Workshop 8

A NNSFC Project: study on cosmic dark energy 1. 2. 3. Theoretical Models of Dark Energy Testing DE Models with Astronomical Data La. MOST Project and Dark Energy (Prof. Y. Zhao’s talk) 4. Chinese Future Astronomical Instruments for Dark Energy Probe (Prof. X. Chen & X. Wu’s talks for 21 CMA; C. -J. Jin’s talk for FAST) 10/31/2020 the 2 nd Sino-French Workshop 9

Dark Energy Models: classification Observation Data Theoretical Assumptions General Relativity Model I 10/31/2020 Model II Cosmo Principle Model III the 2 nd Sino-French Workshop 10

Dark Energy Models: our proposals: motivation w seems to cross -1 Huterer & Cooray, PRD, 71 (2005) 023506, astro-ph/0404062 10/31/2020 the 2 nd Sino-French Workshop 11

Dark Energy Models: our proposals: quintom If the running of w(z), especially a transition across – 1, confirmed in the future, big challenge to the model building * Vacuum : w=-1 * Quintessence: w>-1 * Phantom: w<-1 * K-essence: w>-1 or w<-1 but cannot across -1 A new scenario of Dark Energy : Quintom (Zhang et al. astro-ph/0404224) 10/31/2020 the 2 nd Sino-French Workshop 12

Dark Energy Models: our proposals: quintom Quintom Model building: Why challenges? No-Go Theorem: Bo Feng et al. astro-ph/0404224 Equation of State w can not cross over -1 if the following Vikman Phys. Rev. D 71, 023515 (2005) conditions are satisfied: I. III. IV. Einstein Gravity Minimal Coupling Single Scalar Field Without higher derivative Gong-Bo Zhao et al. astro-ph/0507482 ……. Hao Wei, Ph. D thesis Examples of Quintom-like Models: 1. two scalar field 2. single scalar field with higher derivative 3. including vector field …… 4. Nonminimal Coupling ……. . 10/31/2020 the 2 nd Sino-French Workshop 13

Detailed study on: Two-field models of Quintom Dark Energy -Xiao-fei Zhang , Hong Li, Yunsong Piao and Xinmin Zhang I. Quintom model with two scalar fields: II. Quintom model with Phantom field and neutrino: Astro-ph/0501652 10/31/2020 the 2 nd Sino-French Workshop 14

Dark Energy Models: our proposals: interacting Chaplygin gas The continuity equation of the interaction system, Note that they are independent of general relativity, or any other gravity theories. H. Zhang & Z. -H. Zhu, PRD, 73 (2006) 043518, 10/31/2020 the 2 nd Sino-French Workshop astro-ph/0509895 15

Dark Energy Models: our proposals: Unruh radiation H. Zhang & Z. -H. Zhu, astro-ph/0607531 See Dr. H. Zhang’s Talk 10/31/2020 the 2 nd Sino-French Workshop 16

Observational Constraints: w from SN, SDSS, WMAP Jun-Qing Xia, Gong-Bo Zhao, Bo Feng, Hong Li and Xinmin Zhang Phys. Rev. D 73, 063521, 2006 10/31/2020 the 2 nd Sino-French Workshop 17

Observational Constraints: on Modified Friedmann Equation (MFE) Cosmology n Standard Friedmann equation ( =0, =0) n Modified Friedman equation (Freese & Lewis 2002) 10/31/2020 the 2 nd Sino-French Workshop 18

Observational Constraints: on MFE Cosmology Summary n Constraints from angular size-redshift data Ø n Constraints from SNe. Ia Ø Ø n Multamaki, Gaztanaga & Manera 2003, MNRAS, 344, 761 Constraints from turnaround redshift of cosmic expansion Ø n Sen & Sen 2003 a, Ap. J, 588, 1; 2003 b, PRD, 68, 023513 Constraints from large-scale structure Ø n Zhu & Fujimoto 2003, Ap. J, 585, 52 Wang, Freese, Gondolo & Lewis 2003, Ap. J, 594, 25 Constraints from CMB (WMAP) Ø n Zhu & Fujimoto 2002, Ap. J, 581, 1 Zhu & Fujimoto 2004, Ap. J, 602, 12 Constraints from SNe. Ia and X-ray mass fraction of clusters Ø Zhu, Fujimoto & He 2004, Ap. J, 603, 365 10/31/2020 the 2 nd Sino-French Workshop 19

Observational Constraints: on MFE Cosmology Parameters of MFE cosmology n (B, n), (zeq, n) or ( m, n) n Hubble Parameter as Function of z, H=H 0 E(z) n The Critical/Matter Density 10/31/2020 the 2 nd Sino-French Workshop 20

Observational Constraints: on MFE Cosmology From SNe. Ia and Fanaroff-Riley type IIb radio galaxies n n n Dimensionless coordinate distance data taken from Daly & Djorgovski 2003, Ap. J, 597, 9 78 SNe. Ia from Perlmutter et al. (1999), Riess et al. (1998, 2001). 20 FRIIb radio galaxies from Daly & Guerra (2002). Z. -H. Zhu et al. 2004, Ap. J, 603, 365 10/31/2020 the 2 nd Sino-French Workshop 21

Observational Constraints: on MFE Cosmology From SNe. Ia and Fanaroff-Riley type IIb radio galaxies n n n A 2 minimization method is used to determine ( m, n). The best fit happans at ( m, n)=(0. 38, -0. 20). The 68. 3% and 95. 4% confidence level in the ( m, n) plane are shown. Z. -H. Zhu et al. 2004, Ap. J, 603, 365 10/31/2020 the 2 nd Sino-French Workshop 22

Galaxy Clusters as a Probe for Cosmology SZ+X-ray Strong Lesning angular diameter distance 10/31/2020 Weak Lensing the 2 nd Sino-French Workshop 23

Galaxy Clusters as a Probe for Cosmology Gas mass fraction in clusters of galaxies assume the gas mass fraction fgas(z) invariant constraints on cosmology (d. A(z) – z relation) 10/31/2020 the 2 nd Sino-French Workshop 24

fgas of galaxy clustres as a cosmological probe Allen et al. 2002, 2003 10/31/2020 the 2 nd Sino-French Workshop 25

Observational Constraints: on MFE Cosmology From X-ray gas mass fraction of clusters n n n fgas data are taken from Allen et al. (2002, 2003). fgas~[DA]3/2 when infered from Xray observations. Generally DASCDM with h=0. 5 is used. The “true” cosmology should be the one making these measured fgas, oi to be invariant with redshift. Z. -H. Zhu et al. 2004, Ap. J, 603, 365 10/31/2020 the 2 nd Sino-French Workshop 26

Observational Constraints: on MFE Cosmology From X-ray gas mass fraction of clusters n n n A 2 minimization method is used to determine ( m, n). Marginalize over b=0. 0205 0. 0018 from QSO HS 0105+ 1619 (O’Meara et al. 2001), b=0. 93 0. 05 from simulations (Bialek et al. 2001) and h=0. 72 0. 08 from Hubble Key Project (Freedman et al. 2001) The best fit happans at ( m, n)= (0. 30, 0. 14). Z. -H. Zhu et al. 2004, Ap. J, 603, 365 10/31/2020 the 2 nd Sino-French Workshop 27

Observational Constraints: on MFE Cosmology From combination analysis of the databases 12( m, n)= 22( m, n)= T 2( m, n)= 12( m, n)+ 22( m, n) Z. -H. Zhu et al. 2004, Ap. J, 603, 365 10/31/2020 the 2 nd Sino-French Workshop 28

Observational Constraints: on MFE Cosmology From combination analysis of the databases n n n At the 95. 4% confidence level, m=0. 30 0. 02, n=0. 06+0. 32 -0. 28. The universe switches from deceleration to acceleration around redshift of (0. 52, 0. 73). The modified term in MFE dominates around redshift of (0. 25, 0. 55). Z. -H. Zhu et al. 2004, Ap. J, 603, 365 10/31/2020 the 2 nd Sino-French Workshop 29

Observational Constraints: on MFE Cosmology From turnaround redshift zq=0 n n zq=0 depends on both of m and n. (see eq. below) For each m, there exists one npeak( m), which leads to a maximum of zq=0. Higher m is, lower zq=0 is. For each zq=0, there exists an upper limit for m, e. g. , zq=0>0. 6, then m<0. 328. 10/31/2020 the 2 nd Sino-French Workshop 30

Observational Constraints: on MFE Cosmology From turnaround redshift zq=0 : equations 10/31/2020 the 2 nd Sino-French Workshop 31

Observational Constraints: on MFE Cosmology From turnaround redshift zq=0 n n The thick solid line is zq=0=0. The cross-hatched area is the present optimistic m=0. 330 0. 035. The dashed lines are m=0. 2 and 0. 4 respectively. The shaded area gives 0. 6 < zq=0 <1. 7. Z. -H. Zhu et al. 2004, Ap. J, 602, 12 10/31/2020 the 2 nd Sino-French Workshop 32

A Brane World Model (BWM): DGP n n A self-accelerating 5 -dimensional BWM With a noncompact, infinite volume extra dimension An ordinary 5 -dimensional Einstein-Hilbert action A 4 -dimensional Ricci scalar term induced on the brane Dvali, Gabadadze & Porrati 2000 10/31/2020 the 2 nd Sino-French Workshop 33

Observational Constraints: on DGP Model Z. -H. Zhu et al. 2005 Ap. J 620, 7 10/31/2020 the 2 nd Sino-French Workshop 34

Observational Constraints: on DGP Model Zhu & Alcaniz 2005 Ap. J 620, 7 10/31/2020 the 2 nd Sino-French Workshop 35

Observational Constraints: on DGP Model Zhu & Alcaniz 2005 Ap. J 620, 7 10/31/2020 the 2 nd Sino-French Workshop 36

Observational Constraints: on DGP Model Z. -K. Guo & Z. -H. Zhu et al. 2006, Ap. J, 646, 1 10/31/2020 the 2 nd Sino-French Workshop 37

Observational Constraints: on DGP Model ( m, rc)=(0. 272, 0. 211) Z. -K. Guo & Z. -H. Zhu et al. 2006, Ap. J, 646, 1 10/31/2020 the 2 nd Sino-French Workshop 38

Observational Constraints: on DGP Model ( m, rc)=(0. 265, 0. 216) Z. -K. Guo & Z. -H. Zhu et al. 2006, Ap. J, 646, 1 10/31/2020 the 2 nd Sino-French Workshop 39

Observational Constraints: on DGP Model Z. -K. Guo & Z. -H. Zhu et al. 2006, Ap. J, 646, 1 10/31/2020 the 2 nd Sino-French Workshop 40

Observational Constraints: on DGP Model Z. -K. Guo & Z. -H. Zhu et al. 2006, Ap. J, 646, 1 10/31/2020 the 2 nd Sino-French Workshop 41

Observational Constraints: on DGP Model Z. -K. Guo & Z. -H. Zhu et al. 2006, Ap. J, 646, 1 10/31/2020 the 2 nd Sino-French Workshop 42

Conclusion n n n Various astronomical observations suggests a universe that is lightweight ( m~1/3), flat and accelerating. Current astronomical data prefer w to cross over -1. Quintom and interacting Chaplygin gas are dark energy models in which w can cross over -1. MFE is an alternative to DE as acceleration mechanism. Combinations of current astronomical data can provide stringent constraints on its model parameters. MFE cosmology can not be the mechanism for acceleration starting from z > 1. 0. DGP model is disfavored by current SNe. Ia and fgas of galaxy clusters. 10/31/2020 the 2 nd Sino-French Workshop 43

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