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تسجيل مستخدم جديدThe redshift dependence of Alcock-Paczynski effect: cosmological constraints from the current and next generation observations
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The tomographic Alcock-Paczynski (AP) test is a robust large-scale structure (LSS) measurement that receives little contamination from the redshift space distortion (RSD). It has placed tight cosmological constraints by using small and intermediate clustering scales of the LSS data. However, previous works have neglected the cross-correlation among different redshift bins, which could cause the statistical uncertainty being underestimated by $sim$20%. In this work, we further improve this method by including this multi-redshifts full correlation. We apply it to the SDSS DR12 galaxies sample and find out that, for $Lambda$CDM, the combination of AP with the Planck+BAO dataset slightly reduces (within 1-$sigma$) $Omega_m$ to $0.304pm0.007$ (68.3% CL). This then leads to a larger $H_0$ and also mildly affects $Omega_b h^2$, $n_s$ and the derived parameters $z_*$, $r_*$, $z_{re}$ but not $tau$, $A_s$ and $sigma_8$. For the flat $w$CDM model, our measurement gives $Omega_m=0.301pm 0.010$ and $w=-1.090pm 0.047$, where the additional AP measurement reduces the error budget by $sim 25%$. When including more parameters into the analysis, the AP method also improves the constraints on $Omega_k$, $sum m_mu$, $N_{rm eff}$ by $20-30%$. Early universe parameters such as $dn_s/d{rm ln}k$ and $r$, however, are unaffected. Assuming the dark energy equation of state $w=w_0+w_a frac{z}{1+z}$, the Planck+BAO+SNIa+$H_0$+AP datasets prefer a dynamical dark energy at $approx1.5 sigma$ CL. Finally, we forecast the cosmological constraints expected from the DESI galaxy survey and find that combining AP with CMB+BAO method would improve the $w_0$-$w_a$ constraint by a factor of $sim 10$.
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We develop an improved Alcock-Paczynski (AP) test method that uses the redshift-space two-point correlation function (2pCF) of galaxies. Cosmological constraints can be obtained by examining the redshift dependence of the normalized 2pCF, which shoul
d not change apart from the expected small non-linear evolution. An incorrect choice of cosmology used to convert redshift to comoving distance will manifest itself as redshift-dependent 2pCF. Our method decomposes the redshift difference of the two-dimensional correlation function into the Legendre polynomials whose amplitudes are modeled by radial fitting functions. Our likelihood analysis with this 2-D fitting scheme tightens the constraints on $Omega_m$ and ${w}$ by $sim 40%$ compared to the method of Li et al. (2016, 2017, 2018) that uses one dimensional angular dependence only. We also find that the correction for the non-linear evolution in the 2pCF has a non-negligible cosmology dependence, which has been neglected in previous similar studies by Li et al.. With an accurate accounting for the non-linear systematics and use of full two-dimensional shape information of the 2pCF down to scales as small as $5~h^{-1}{rm Mpc}$ it is expected that the AP test with redshift-space galaxy clustering anisotropy can be a powerful method to constrain the expansion history of the universe.
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