分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We construct a three-dimensional and redshift-evolutionary X-ray and ultraviolet ($L_X-L_{UV}$) luminosity relation for quasars from the powerful statistic tool called copula, and find that the constructed $L_X-L_{UV}$ relation from copula is more viable than the standard one and the observations favor the redshift-evolutionary relation more than $3\sigma$. The Akaike and Bayes information criterions indicate that the quasar data support strongly the three-dimensional $L_X-L_{UV}$ relation. Our results show that the quasars can be regarded as a reliable indicator of the cosmic distance if the $L_X-L_{UV}$ relation from copula is used to calibrate quasar data.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We construct a three-dimensional and redshift-evolutionary X-ray and ultraviolet ($L_X-L_{UV}$) luminosity relation for quasars from the powerful statistic tool called copula, and find that the constructed $L_X-L_{UV}$ relation from copula is more viable than the standard one and the observations favor the redshift-evolutionary relation more than $3\sigma$. The Akaike and Bayes information criterions indicate that the quasar data support strongly the three-dimensional $L_X-L_{UV}$ relation. Our results show that the quasars can be regarded as a reliable indicator of the cosmic distance if the $L_X-L_{UV}$ relation from copula is used to calibrate quasar data.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In this paper, we obtain two improved Amati correlations of the Gamma-Ray burst (GRB) data via a powerful statistical tool called copula. After calibrating, with the low-redshift GRB data, the improved Amati correlations based on a fiducial $\Lambda$CDM model with $\Omega_\mathrm{m0}=0.3$ and $H_0=70~\mathrm{km~s^{-1}Mpc^{-1}}$, and extrapolating the results to the high-redshift GRB data, we obtain the Hubble diagram of GRB data points. Applying these GRB data to constrain the $\Lambda$CDM model, we find that the improved Amati correlation from copula can give a result well consistent with $\Omega_\mathrm{m0}=0.3$, while the standard Amati and extended Amati correlations do not. This results suggest that when the improved Amati correlation from copula is used in the low-redshift calibration method, the GRB data can be regarded as a viable cosmological explorer. However, the Bayesian information criterion indicates that the standard Amati correlation remains to be favored mildly since it has the least model parameters. Furthermore, once the simultaneous fitting method rather than the low-redshift calibration one is used, there is no apparent evidence that the improved Amati correlation is better than the standard one. Thus, more works need to be done in the future in order to compare different Amati correlations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： An improved Amati correlation was constructed in (ApJ 931 (2022) 50) by us recently. In this paper, we further study constraints on the $\Lambda$CDM and $w$CDM models from the gamma ray bursts (GRBs) standardized with the standard and improved Amati correlations, respectively. By using the Pantheon type Ia supernova sample to calibrate the latest A220 GRB data set, the GRB Hubble diagram is obtained model-independently. We find that at the high redshift region ($z>1.4$) the GRB distance modulus from the improved Amati correlation is larger apparently than that from the standard Amati one. The GRB data from the standard Amati correlation only give a lower bound limit on the present matter density parameter $\Omega_{\mathrm{m0}}$, while the GRBs from the improved Amati correlation constrain the $\Omega_{\mathrm{m0}}$ with the $68\%$ confidence level to be $0.308^{+0.066}_{-0.230}$ and $0.307^{+0.057}_{-0.290}$ in the $\Lambda$CDM and $w$CDM models, respectively, which are consistent very well with those given by other current popular observational data including BAO, CMB and so on. Once the $H(z)$ data are added in our analysis, the constraint on the Hubble constant $H_0$ can be achieved. We find that two different correlations provide slightly different $H_0$ results but the marginalized mean values seem to be close to that from the Planck 2018 CMB observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Recently, an indicative evidence of a stochastic process, reported by the NANOGrav Collaboration based on the analysis of 12.5-year pulsar timing array data which might be interpreted as a potential stochastic gravitational wave signal, has aroused keen interest of theorists. The first-order color charge confinement phase transition at the QCD scale could be one of the cosmological sources for the NANOGrav signal. If the phase transition is flavor dependent and happens sequentially, it is important to find that what kind of QCD matter in which the first-order confinement/deconfinement phase transition happens is more likely to be the potential source of the NANOGrav signal during the evolution of the universe. In this paper, we would like to illustrate that the NANOGrav signal could be generated from confinement/deconfinement transition in either heavy static quarks with a zero baryon chemical potential, or quarks with a finite baryon chemical potential. In contrast, the gluon confinement could not possibly be the source for the NANOGrav signal according to the current observation. Future observation will help to distinguish between different scenarios.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In this paper, we calibrate the Amati relation (the $E_{\rm p}$-${E}_{\rm
iso}$ correlation) of gamma-ray bursts (GRBs) in a cosmology-independent way.
By using Gaussian process to reconstruct the smoothed luminosity distance from
the Pantheon type Ia supernovae (SNe Ia) sample, we utilize the reconstructed
results to calibrate the $E_{\rm p}$-${E}_{\rm iso}$ correlation with the
Markov Chain Monte Carlo method and construct a Hubble diagram with the A220
GRB data, in which there are A118 GRB data with the higher qualities
appropriate for cosmological purposes. With 98 GRBs at $1.4
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We establish a new cosmological-model-independent method to determine the
Hubble constant $H_0$ from the localized FRBs and the Hubble parameter
measurements and obtain a first such determination
$H_0=70.60\pm2.11~\mathrm{km/s/Mpc}$ of about 3.00\% uncertainty with data from
the eighteen localized FRBs and nineteen Hubble parameter measurements in the
redshift range $0
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We establish a new cosmological-model-independent method to determine the
Hubble constant $H_0$ from the localized FRBs and the Hubble parameter
measurements and obtain a first such determination
$H_0=70.60\pm2.11~\mathrm{km/s/Mpc}$ of about 3.00\% uncertainty with data from
the eighteen localized FRBs and nineteen Hubble parameter measurements in the
redshift range $0
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In this paper, we calibrate the Amati relation (the $E_{\rm p}$-${E}_{\rm
iso}$ correlation) of gamma-ray bursts (GRBs) in a cosmology-independent way.
By using Gaussian process to reconstruct the smoothed luminosity distance from
the Pantheon type Ia supernovae (SNe Ia) sample, we utilize the reconstructed
results to calibrate the $E_{\rm p}$-${E}_{\rm iso}$ correlation with the
Markov Chain Monte Carlo method and construct a Hubble diagram with the A220
GRB data, in which there are A118 GRB data with the higher qualities
appropriate for cosmological purposes. With 98 GRBs at $1.4
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