arXiv subjects

Jiaze Gao

Publications and source records attributed to Jiaze Gao.

9 recordsLinked to original sources

arXiv2026

Redshift-Dependent Intrinsic Dispersion in the Quasar UV/X-ray Luminosity Relation

Accurate modeling of the intrinsic dispersion in the quasar UV/X-ray luminosity relation is essential for reliable cosmological inference. We investigate its redshift dependence using luminosity distances reconstructed from cosmic chronometer and baryon acoustic oscillation measurements through Gaussian-process (GP) regression. Bayesian model comparison and posterior constraints show that the intrinsic dispersion is not well described by a single redshift-independent constant over $0.7<z<2.6$. It remains approximately constant at $0.7<z<1.6$, but shows an overall decreasing trend in the higher-redshift interval $1.6<z<2.6$, where the redshift-dependent intrinsic-dispersion model is decisively favored. This conclusion remains qualitatively robust against changes in the scaling-relation parameterization, GP kernel, and redshift binning scheme. We further examine its impact on cosmological inference in the flat $Λ$CDM model and find that, under the adopted calibration setup, the redshift-dependent intrinsic-dispersion model shifts the posterior median of $Ω_{\rm m0}$ by $ΔΩ_{\rm m0}\simeq 0.025$. This indicates that intrinsic-dispersion modeling is a non-negligible component of the systematic-error budget for quasar cosmology and should be accounted for in future precision analyses.

astro-ph.CO↗

arXiv2026

Deep Learning Calibration of the Quasar X-ray/UV Luminosity Relation for Cosmological Applications

Quasars can serve as standard candles through an empirical scaling relation between their ultraviolet (UV) and X-ray luminosities. As high-redshift probes, it is critical to test whether this relation evolves with redshift. In this work, we reconstruct the Hubble diagram of the Pantheon+ sample using the deep learning--based LADDER algorithm and use it as a reference to investigate the quasar scaling relation. Our results, which are consistent with those from Gaussian process regression and narrow-bin analyses, show that the potentially contaminated sample at $z<0.7$ differs significantly from the $z>0.7$ sample; thus, it should be further screened or excluded when quasars are used as cosmological probes. We find that the scaling relation exhibits a non-linear redshift dependence that cannot be accounted for by a simple linear correction, and that this behavior is a feature of the current data sample rather than a consequence of cosmological model misspecification. To use quasars as standardizable candles, further modeling of the scaling relation and intrinsic dispersion, or more advanced data processing techniques, is required.

astro-ph.CO↗

arXiv2026

New Dynamical Measurements from a Lensed Quasar Sample: Joint Analysis Constrains the Mass Profile Evolution of Lens Galaxies

We present a systematic study of the internal mass structure of early-type galaxies (ETGs) based on 106 galaxy-scale strong gravitational lenses with background quasars, all having spectroscopic redshifts. From this parent sample, we select 24 systems with high-quality ancillary data for joint analysis of strong lensing geometry and stellar kinematics. A key contribution is the derivation of new single-aperture stellar velocity dispersions for 11 lens galaxies via an iterative spectroscopic fitting procedure that mitigates quasar contamination, providing previously unavailable data. We model the total mass-density profile as a power law, $ρ\propto r^{-γ}$, and parameterise its logarithmic slope as $γ= γ_0 + γ_z \cdot z_l + γ_s \cdot \log \tildeΣ$, where $z_l$ is the lens redshift and $\tildeΣ$ the surface mass density. Within a flat $Λ$CDM framework and using DESI BAO measurements as a prior, we constrain the parameters via Monte Carlo nested sampling to $γ_0 = 1.62^{+0.11}_{-0.12}$, $γ_z = -0.35^{+0.08}_{-0.09}$, and $γ_s = 0.37^{+0.08}_{-0.07}$ ($68\%$ confidence intervals). Our results robustly demonstrate that $γ$ increases with surface mass density ($γ_s > 0$) and decreases with redshift ($γ_z < 0$). This implies that, at fixed redshift, galaxies with denser stellar cores have steeper mass profiles, while at fixed density, profiles become shallower at higher redshifts. By successfully applying the joint lensing--dynamics method to a substantial, independently acquired sample of lensed quasars, this work provides crucial validation of structural trends previously observed in galaxy--galaxy lensing systems, reinforcing the established evolutionary picture for massive ETGs and establishing lensed quasars as a potent probe of galaxy structure.

astro-ph.GA↗

arXiv2026

Redshift Evolution of the HII Galaxy $L$-$σ$ Relation: Gaussian Process Analysis and Cosmological Implications

The empirical correlation between the H$β$ luminosity ($L$) and the ionized gas velocity dispersion ($σ$) in HII starburst galaxies (HIIGs) provides a foundation for using them as cosmological standard candles. A key unresolved issue is whether this $L$-$σ$ relation changes with redshift, which would impact its application at high redshifts. We test for possible evolution using cosmology-independent distance estimates up to $z \sim 1.8$, obtained from Gaussian Process regression of the Pantheon+ Type Ia supernovae Hubble diagram. These distances allow us to compare the standard $L$-$σ$ relation with three redshift-dependent extensions through Bayesian model comparison. We find that a logarithmic redshift correction is statistically preferred when the intrinsic dispersion of the relation is explicitly modeled, significantly improving the fit to high-$z$ data. However, the evidence for evolution strongly depends on how the likelihood function accounts for this intrinsic dispersion and is weaker if it is ignored. We also show that Malmquist bias significantly affects comparisons between low- and high-$z$ samples, reducing -- though not eliminating -- the statistical preference for redshift evolution after matching luminosity ranges. These results indicate that current HIIG data favor a redshift-dependent modification of the standard $L$-$σ$ relation, while highlighting the critical role of selection effects and intrinsic dispersion modeling in establishing HIIGs as precise cosmological probes.

astro-ph.CO↗

arXiv2025

Constraints on transition redshift utilizing the latest H(z) measurements and comments on the Hubble tension

The motivation of this paper is to obtain reliable constraints of transition redshift ($z_{ztr}$) and, in combination with the evolution of the Hubble constant ($H_{0}$) that could alleviate the Hubble tension, discuss the possible origin of the tension. Utilizing the latest H(z) measurements and different methods ($Λ$CDM model, Cosmography, and Gaussian process method), we investigated the impact of methodology and dataset on $z_{ztr}$ constraints, and find that the choice of method has a greater impact on $z_{tr}$ than the observations themselves. Through a statistical analysis of the $z_{ztr}$ constraints from 2004 to 2024, we find that total $z_{tr}$ constraints (2004$-$2024) can be well described by a Gaussian function with the mean value 0.65 and the standard deviation 0.16; that is, $\bar{z}_{tr}$(all) = 0.65 $\pm$ 0.16. And we confirmed that both dataset and methodology can indeed significantly affect the final constraints. The screened $z_{tr}$ constraints with free $H_{0}$ gives a new result $\bar{z}_{tr}$(free) = 0.64 $\pm$ 0.16. Coincidentally, the $z_{tr}$ results overlap with the initial moment of $H_{0}$ evolution ($H_{0}$ value starts to deviate from the Planck result). This may suggest that the Hubble tension might be closely related to this particular period in the evolution of the Universe.

astro-ph.CO↗

arXiv2024

Detection of gamma-ray burst Amati relation based on Hubble data set and Pantheon+ samples

Using gamma-ray bursts as standard candles for cosmological parameter constraints rely on their empirical luminosity relations and low-redshift calibration. In this paper, we examine the Amati relation and its potential corrections based on the A118 sample of higher-quality gamma-ray bursts, using both Hubble data set and Pantheon+ samples as calibration samples in the redshift range of z < 1.965. In calibrating gamma-ray bursts using these two datasets, we employ Gaussian processes to obtain corresponding Hubble diagrams to avoid the dependence on cosmological models in the calibration process. We first divided the low-redshift sample of GRBs into two bins and examined the Amati relation and its potential modifications. We found that under both calibrations, the Amati relation did not show evidence of redshift evolution (68% confidence level). For the other two Amati relations that include redshift evolution terms, the central values of the redshift evolution coefficients deviated from 0, but due to the limitations of the sample size and the increase in the number of parameters, most of the redshift evolution coefficients were not able to be excluded from 0 at the 1 sigma level. Therefore, to assess their situation across the entire redshift range, we employed MCMC to globally fit three types of Amati relations. By computing AIC and BIC, we found that for the GRB A118 sample, the standard Amati relation remains the most fitting empirical luminosity formula, and no potential redshift evolution trend was observed for two different low-redshift calibrating sources.

astro-ph.CO↗

arXiv2024

Mitigating Cosmological Tensions via Momentum-Coupled Dark Sector Model

In this paper, we investigate the momentum coupling between early dark energy (EDE) and cold dark matter to alleviate cosmological tensions. EDE has exhibited promising efficacy in addressing the Hubble tension, but it exacerbates the large-scale structure tension. We consider the interaction between EDE and cold dark matter, introducing a pure momentum exchange between them to alleviate the large-scale structure tension introduced by the EDE model. We find that this coupling model is consistent with the EDE model, yielding a higher value for $H_0$, which can resolve the Hubble tension. Additionally, the new model exhibits a suppressive effect on structure growth, contributing to the alleviation of the large-scale structure tension. By utilizing the Markov Chain Monte Carlo method and incorporating various cosmological data, the coupling model constrains the best-fit values for $H_0$ to be $72.23$ km/s/Mpc and for $S_8$ to be 0.8192. Compared to the $Λ$CDM model, the new models have not fully resolved the large-scale structure tension. However, in contrast to the best-fit value of 0.8316 for $S_8$ obtained from the EDE model, the new model alleviates the negative impact of the EDE model.

astro-ph.CO↗

arXiv2024

Coupled Dark Sector Models and Cosmological Tensions

In this paper, we introduce two coupling models of early dark energy (EDE) and cold dark matter aimed at alleviating cosmological tensions. We utilize the EDE component in the coupling models to relieve the Hubble tension, while leveraging the interaction between dark matter and dark energy to alleviate the large-scale structure tension. The interaction is implemented in the form of pure momentum coupling and Yukawa coupling. We employed various cosmological datasets, including cosmic microwave background radiation, baryon acoustic oscillations, Type Ia supernovae, the local distance-ladder data (SH0ES), and the Dark Energy Survey Year-3 data, to analyze our models. We first exclude SH0ES data from the entire dataset to constrain the parameters of novel models. We observe that the constraints on $H_0$ from two coupling models are slightly higher than that from the $Λ$CDM model, but they exhibit a significant inconsistency with the SH0ES data, consistent with prior research findings in the EDE model. Subsequently, we incorporate SH0ES data to re-constrain the parameters of various models, our findings reveal that both coupling models yield best-fit values for $H_0$ approximately around $72.23$ km/s/Mpc, effectively mitigating the Hubble tension. Similar to the EDE model, the coupling models yield the $S_8$ values that still surpasses the result of the $Λ$CDM model. Nevertheless, the best-fit values for $S_8$ obtained with the two new models are 0.8192 and 0.8177, respectively, which are lower than the 0.8316 achieved by the EDE model. Consequently, although our coupling models fail to fully resolve the large-scale structure tension, they partially mitigate the adverse effect of the original EDE model.

astro-ph.CO↗

arXiv2023

A Measurement of Hubble Constant Using Cosmographic Approach from Fast Radio Bursts and SNe Ia

The Hubble constant ${H}_0$ is a crucial parameter in cosmology. However, different cosmic observations have resulted in varying posterior results for ${H}_0$, leading to what is known as the ${H}_0$ tension. In order to address this issue, it is beneficial to use other dataset to constrain ${H}_0$. In this paper, via the cosmographic approach based on the Friedman-Lemaitre-Robertson-Walker (FLRW) metric to the dispersion measure of the intergalactic medium ${\rm{DM}}_{\rm{IGM}}(z)$ of Fast Radio Bursts (FRBs), we obtain the Taylor expansion of $\langle{\rm{DM}}_{\rm{IGM}}(z)\rangle$ in terms redshift $z$. The result for Hubble constant $H_0=65.5^{+6.4}_{-5.4}$ ${\rm{km~s^{-1}~Mpc^{-1}}}$ $(68$$\%$ ${\rm{C.L.}}) $, cosmological deceleration parameter $q_0=-0.50\pm 0.20 $ and the jerk parameter $j_0=-0.1^{+2.0}_{-2.5}$ using uncalibrated Supernova Ia (SNe Ia) Pantheon dataset combined with 18 localized FRBs are obtained. To demonstrate the impact of parameter degeneracies on our analysis methods, we compare the results using three different forms of $f_{\rm{IGM}}(z)$ and two different prior distributions for $Ω_{\rm{b,0}}$. Then we find that the uncertainty in $H_0$ is not significantly affected by the prior range of $f_{\rm{IGM}}(z)$ and $Ω_{\rm{b,0}}$, but the mean value is influenced by the priors for $f_{\rm{IGM}}(z)$ and $Ω_{\rm{b,0}}$ due to parameter degeneracies with $H_0$. Employing $f_{\rm{IGM}}(z)$ that evolves with redshift, we obtain the constraints for $H_0=69.0^{+6.7}_{-5.7}$ ${\rm{km~s^{-1}~Mpc^{-1}}}$. Furthermore, the mock analyses give a posterior estimation of $H_0$ with an accuracy of 4.6\% and higher precision for $q_0$ and $j_0$ in the near future.

astro-ph.CO↗