arXiv subjects

Zhuoyang Li

Publications and source records attributed to Zhuoyang Li.

22 records · Page 2Linked to original sources

arXiv2024

Mass reconstruction and noise reduction with cosmic-web environments

The clustering of galaxies and their connections to their initial conditions is a major means by which we learn about cosmology. However, the stochasticity between galaxies and their underlying matter field is a major limitation for precise measurements of galaxy clustering. Efforts have been made with an optimal weighting scheme to reduce this stochasticity using the mass-dependent clustering of dark matter haloes. Here, we show that this is not optimal. We demonstrate that the cosmic-web environments (voids, sheets, filaments \& knots) of haloes, when combined linearly with the linear bias, provide extra information for reducing stochasticity in terms of two-point statistics. Using the environmental information alone can increase the signal-to-noise of clustering by a factor of 3 better than the white-noise level at the scales of the baryon acoustic oscillations. The information about the environment and halo mass are complementary. Their combination increases the signal-to-noise by another factor of 2-3. The information about the cosmic web correlates with other properties of haloes, including halo concentrations and tidal forces -- all are related to the assembly bias of haloes.

astro-ph.CO↗

arXiv2022

Redshift Evolution and Non-Universal Dispersion of Quasar Luminosity Correlation

The standard $Λ$CDM model is recently reported to deviate from the high-redshift Hubble diagram of type Ia supernovae (SNe) and quasars (QSOs) at $\sim4σ$ confidence level. In this work, we combine the PAge approximation (a nearly model-independent parameterization) and a high-quality QSO sample to search for the origins of the deviation. By visualizing the $Λ$CDM model and the marginalized $3σ$ constraints of SNe+QSOs into PAge space, we confirm that the SNe+QSOs constraints in both flat and non-flat PAge cases are in remarkable tension with the standard $Λ$CDM cosmology. Next, we investigate the tension from the perspective of redshift-evolution effects. We find that the QSO correlation coefficient $γ$ calibrated by SNe+low-z QSOs and SNe+high-z QSOs shows $\sim2.7σ$ and $\sim4σ$ tensions in flat and non-flat universes, respectively. The tensions for intrinsic dispersion $δ$ between different data sets are found to be $>4σ$ in both flat and non-flat cases. These results indicate that the QSO luminosity correlation suffers from significant redshift evolution and non-universal intrinsic dispersion. Using a redshift-dependence correlation to build QSO Hubble diagram could lead to biases. Thus, the $\sim4σ$ deviation from the standard $Λ$CDM probably originates from the redshift-evolution effects and non-universal dispersion of the QSO luminosity correlation rather than new physics.

astro-ph.CO↗

arXiv2022

The $S_8$ Tension in Light of Updated Redshift-Space Distortion Data and PAge Approximation

One of the most prominent challenges to the standard Lambda cold dark matter ($Λ$CDM) cosmology is the tension between the structure growth parameter $S_8$ constrained by the cosmic microwave background (CMB) data and the smaller one suggested by the cosmic shear data. Recent studies show that, for $Λ$CDM cosmology, redshift-space distortion (RSD) data also prefers a smaller $S_8$ that is $\sim 2$-$3σ$ lower than the CMB value, but the result is sensitive to the cosmological model. In the present work we update the RSD constraint on $S_8$ with the most up-to-date RSD data set where the correlation between data points are properly taken into account. To reduce the model dependence, we add in our Monte Carlo Markov Chain calculation the most up-to-date data sets of Type Ia supernovae (SN) and baryon acoustic oscillations (BAO), whose correlation with RSD is also taken into account, to constrain the background geometry. For $Λ$CDM cosmology we find $S_8= 0.812 \pm 0.026$, which is $\sim 2σ$ larger than previous studies, and hence is consistent with the CMB constraint. By replacing $Λ$CDM with the Parameterization based on cosmic Age (PAge), an almost model-independent description of the late universe, we find that the RSD + SN + BAO constraint on $S_8$ is insensitive to the cosmological model.

astro-ph.CO↗

arXiv2021

A More Accurate Parameterization based on cosmic Age (MAPAge)

Recently, several statistically significant tensions between different cosmological datasets have raised doubts about the standard Lambda cold dark matter ($Λ$CDM) model. A recent letter~\citet{Huang:2020mub} suggests to use "Parameterization based on cosmic Age" (PAge) to approximate a broad class of beyond-$Λ$CDM models, with a typical accuracy $\sim 1\%$ in angular diameter distances at $z\lesssim 10$. In this work, we extend PAge to a More Accurate Parameterization based on cosmic Age (MAPAge) by adding a new degree of freedom $η_2$. The parameter $η_2$ describes the difference between physically motivated models and their phenomenological PAge approximations. The accuracy of MAPAge, typically of order $10^{-3}$ in angular diameter distances at $z\lesssim 10$, is significantly better than PAge. We compare PAge and MAPAge with current observational data and forecast data. The conjecture in~\citet{Huang:2020mub}, that PAge approximation is sufficiently good for current observations, is quantitatively confirmed in this work. We also show that the extension from PAge to MAPAge is important for future observations, which typically requires sub-percent accuracy in theoretical predictions.

astro-ph.CO↗