分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Neutral hydrogen (HI) intensity mapping (IM) survey is generally regarded as a promising tool to explore the expansion history of the universe. In this work, we investigate the capability of MeerKAT HI IM observation in interferometric mode to estimate the power spectrum and constrain cosmological parameters in typical dark energy models. Besides, a novel approach of delay spectrum is employed, which can achieve separating the weak HI signal from the foreground in the frequency space. We find that the different survey fields have a great influence on the fractional errors on power spectrum $\Delta P/P$ in a limited observational time of 10 h. With the integration time increasing from 10 h to 10000 h, $\Delta P/P$ becomes distinctly smaller until the cosmic variance begins to dominate. In the total 10000 h observation, the lower $\Delta P/P$ in low $k$ can be achieved when tracking 100 points for MeerKAT L-band and 10 points for MeerKAT UHF-band. Through simulating 10000 h HI IM survey, we obtain $\sigma(\Omega_{\rm m})=0.044$ and $\sigma(H_0)=2.8~{\rm kms^{-1}\ Mpc^{-1}}$ with MeerKAT L-band, which are worse than the results of $\sigma(\Omega_{\rm m})=0.028$ and $\sigma(H_0)=2.0~{\rm km\ s^{-1}\ Mpc^{-1}}$ with MeerKAT UHF-band in the $\Lambda$CDM model. However, in the $w$CDM and CPL models, MeerKAT shows a limited capability of constraining dark-energy equation of state, even though combined with Planck data. Our analysis is shown to be a useful guide for the near future MeerKAT observations in HI IM survey.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The 21 cm intensity mapping (IM) technique provides us with an efficient way
to observe the cosmic large-scale structure (LSS). From the LSS data, one can
use the baryon acoustic oscillation and redshift space distortion to trace the
expansion and growth history of the universe, and thus measure the dark energy
parameters. In this paper, we make a forecast for cosmological parameter
estimation with the synergy of three 21 cm IM experiments. Specifically, we
adopt a novel joint survey strategy, FAST ($0
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The 21 cm intensity mapping (IM) technique provides us with an efficient way
to observe the cosmic large-scale structure (LSS). From the LSS data, one can
use the baryon acoustic oscillation and redshift space distortion to trace the
expansion and growth history of the universe, and thus measure the dark energy
parameters. In this paper, we make a forecast for cosmological parameter
estimation with the synergy of three 21 cm IM experiments. Specifically, we
adopt a novel joint survey strategy, FAST ($0
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Using the measurements of tidal deformations in the binary neutron star (BNS) coalescences can obtain the information of redshifts of gravitational wave (GW) sources, and thus actually the cosmic expansion history can be investigated by solely using such GW dark sirens. To do this, the key is to get large amounts of accurate GW data, which can be achieved by employing the third-generation (3G) GW detectors. In this paper, we wish to offer an answer to the question of whether the Hubble constant and the equation of state (EoS) of dark energy can be precisely measured by solely using GW dark sirens. We find that in the era of 3G GW detectors ${\cal O}(10^5)$-${\cal O}(10^6)$ dark siren data (with the tidal measurements) can be obtained in a several-year observation, and thus using only dark sirens can actually achieve the precision cosmology. Based on a network of 3G detectors, we obtain the constraint precisions of $0.1\%$ and $0.6\%$ for the Hubble constant $H_0$ and the constant EoS of dark energy $w$, respectively; for a two-parameter EoS parametrization of dark energy, the precision of $w_0$ is $1.4\%$ and the error of $w_a$ is 0.086. We conclude that 3G GW detectors would lead to breakthroughs in solving the Hubble tension and revealing the nature of dark energy.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Gravitational waves (GWs) from the compact binary coalescences can be used as standard sirens to explore the cosmic expansion history. In the next decades, it is anticipated that we could obtain the multi-band GW standard siren data (from nanohertz to a few hundred hertz), which are expected to play an important role in cosmological parameter estimation. In this work, we give for the first time the joint constraints on cosmological parameters using the future multi-band GW standard siren observations. We simulate the multi-band GW standard sirens based on the SKA-era pulsar timing array (PTA), the Taiji observatory, and the Cosmic Explorer (CE) to perform cosmological analysis. In the $\Lambda$CDM model, we find that the joint PTA+Taiji+CE data could provide a tight constraint on the Hubble constant with a $0.5\%$ precision. Moreover, PTA+Taiji+CE could break the cosmological parameter degeneracies generated by CMB, especially in the dynamical dark energy models. When combining the PTA+Taiji+CE data with the CMB data, the constraint precisions of $\Omega_{\rm m}$ and $H_0$ are $1.0\%$ and $0.3\%$, meeting the standard of precision cosmology. The joint CMB+PTA+Taiji+CE data give $\sigma(w)=0.028$ in the $w$CDM model and $\sigma(w_0)=0.11$ and $\sigma(w_a)=0.32$ in the $w_0w_a$CDM model, which are comparable with or close to the latest constraint results by the CMB+BAO+SN. In conclusion, it is worth expecting to use the future multi-band GW observations to explore the nature of dark energy and measure the Hubble constant.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Ultra-low-frequency gravitational waves (GWs) generated by individual inspiraling supermassive black hole binaries (SMBHBs) in the centers of galaxies may be detected by pulsar timing arrays (PTAs) in the future. These GW signals encoding absolute cosmic distances can serve as bright and dark sirens, having potential to be developed into a precise cosmological probe. Here we show that an SKA-era PTA consisting of 100 millisecond pulsars may observe about 20 bright sirens and 90 dark sirens during a 10-year observation. The bright sirens, together with the CMB data, have comparable capabilities to current mainstream data for measuring the equation of state of dark energy. The dark sirens could make the measurement precision of the Hubble constant far beyond the standard of precision cosmology. Our results indicate that ultra-low-frequency GWs from individual SMBHBs are of great significance in exploring the nature of dark energy and measuring the Hubble constant.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Measurements of time-delay cosmography of lensed quasars can provide an independent probe to explore the expansion history of the late-time Universe. In this paper, we employ the time-delay cosmography measurements from seven lenses (here abbreviated as the TD data) to constrain interacting dark energy (IDE) models. We mainly focus on the scenario of vacuum energy (with $w=-1$) interacting with cold dark matter, and consider four typical cases of the interaction form $Q$. When the TD data alone are employed, we find that the IDE models with $Q\propto \rho_{\rm de}$ seem to have an advantage in relieving the $H_{0}$ tension between the cosmic microwave background (CMB) and TD data. When the TD data are added to the CMB$+$BAO$+$SN$+H_0$ data, we find that: (i) the coupling parameter $\beta$ in all the considered IDE models is positive within 1$\sigma$ range, implying a mild preference for the case of cold dark matter decaying into dark energy; (ii) the IDE model with $Q = \beta H_{0} \rho_{\rm c}$ slightly relieves the $S_8$ tension, but the other considered IDE models further aggravate this tension; (iii) the Akaike information criteria of the IDE models with $Q \propto \rho_{\rm c}$ are lower than that of the $\Lambda$CDM model, indicating that these IDE models are more preferred by the current mainstream data. We conclude that the considered IDE models have their own different advantages when the TD data are employed, and none of them can achieve good scores in all aspects.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： With the measurement of the electromagnetic (EM) counterpart, a gravitational wave (GW) event could be treated as a standard siren. As a novel cosmological probe, the standard siren will bring significant implications for cosmology. In this paper, by considering the coincident detections of GW and associated $\gamma$ ray burst (GRB), we find that only about 400 GW bright standard sirens from binary neutron star mergers could be detected in a 10-year observation of the Einstein Telescope and the THESEUS satellite mission. Based on this mock sample, we investigate the implications of GW standard sirens on the interaction between dark energy and dark matter. In our analysis, four viable interacting dark energy (IDE) models, with interaction forms $Q=3\beta H \rho_{\mathrm{de}}$ and $Q=3 \beta H \rho_{\mathrm{c}}$, are considered. Compared with the traditional EM observational data such as CMB, BAO, and SN Ia, the combination of both GW and EM observations could effectively break the degeneracies between different cosmological parameters and provide more stringent cosmological fits. We also find that the GW data could play a more important role for determining the interaction in the models with $Q=3 \beta H \rho_{\mathrm{c}}$, compared with the models with $Q=3\beta H \rho_{\mathrm{de}}$.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Although the cosmic curvature has been tightly constrained in the standard cosmological model using observations of cosmic microwave background anisotropies, it is still of great importance to independently measure this key parameter using only late-universe observations in a cosmological model-independent way. The distance sum rule in strong gravitational lensing (SGL) provides such a way, provided that the three distances in the sum rule can be calibrated by other observations. In this paper, we propose that gravitational waves (GWs) can be used to provide the distance calibration in the SGL method, which can avoid the dependence on distance ladder and cover a wider redshift range. Using the simulated GW standard siren observation by the Einstein Telescope as an example, we show that this scheme is feasible and advantageous. We find that $\Delta\Omega_k\simeq 0.17$ with the current SGL data, which is slightly more precise than the case of using SN to calibrate. Furthermore, we consider the forthcoming LSST survey that is expected to observe many SGL systems, and we find that about $10^4$ SGL data could provide the precise measurement of $\Delta\Omega_k\simeq 10^{-2}$ with the help of GWs. In addition, our results confirm that this method of constraining $\Omega_k$ is strongly dependent on lens models. However, obtaining a more accurate phenomenological model for lens galaxies is highly predictable as future massive surveys observe more and more SGL samples, which will significantly improve the constraint of cosmic curvature.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Fast radio bursts (FRBs) can be used to measure the Hubble constant by employing the Macquart relation. However, at present, only a small number of FRB events are localized to their host galaxies with known redshifts. In this paper, we develop a Bayesian method to statistically measure the Hubble constant using unlocalized FRBs and galaxy catalog data, which makes it possible to constrain cosmological parameters by using a large number of FRB data without known redshift information. Using the six FRB events observed by ASKAP combined with the big bang nucleosynthesis result, we obtain $H_0=71.7^{+8.8}_{-7.4}$ km s$^{-1}$ Mpc$^{-1}$ in the simulation-based case and $H_0=71.5^{+10.0}_{-8.1}$ km s$^{-1}$ Mpc$^{-1}$ in the observation-based case ($68\%$ highest-density interval), assuming different host galaxy population parameters. We also estimate that in the next few years, using thousands of FRBs could achieve a $3\%$ precision on the random error of the Hubble constant.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Gravitational waves (GWs) from compact binary coalescences encode the absolute luminosity distances of GW sources. Once the redshifts of GW sources are known, one can use the distance-redshift relation to constrain cosmological parameters. One way to obtain the redshifts is to localize GW sources by GW observations and then use galaxy catalogs to determine redshifts from a statistical analysis of redshift information of the potential host galaxies, and such GW data are commonly referred to as dark sirens. The third-generation (3G) GW detectors are planned to work in the 2030s and will observe numerous compact binary coalescences. Using these GW events as dark sirens requires high-quality galaxy catalogs from future sky survey projects. The China Space Station Telescope (CSST) will be launched in 2024 and will observe billions of galaxies within a 17500 deg$^2$ survey area up to $z\sim 4$, providing photometric and spectroscopic galaxy catalogs. In this work, we simulate the CSST galaxy catalog and the 5-year GW data, and combine them to infer the Hubble constant ($H_0$). Our results show that the measurement precision of $H_0$ could reach better than $0.005\%$, which is an astonishing precision for the Hubble constant measurement. We conclude that the synergy between the 3G GW detectors and CSST will be of far-reaching importance in dark-siren cosmology.
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