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Superluminous supernovae (SLSNe) are a class of intense celestial events that can be standardized for measuring cosmological parameters, bridging the gap between type Ia supernovae and the cosmic microwave background. In this work, we discuss the cosmological applications of SLSNe from the Chinese Space Station Telescope (CSST). Our estimation suggests that SLSNe rate is biased tracing the cosmic star formation rate, exhibiting a factor of (1 + z)1.2. We futher predict that CSST is poised to observe ∼ 360 SLSNe in the 10 square degrees ultra-deep field survey within a span of 2.5 years. A stringent constraint on cosmological parameters can be derived from their peak-color relationship. CSST is anticipated to uncover a substantial number of SLSNe, contributing to a deeper understanding of their central engines and shedding light on the nature of dark energy at high redshifts. [ABSTRACT FROM AUTHOR]

The FAST All Sky Hi survey (FASHI) was designed to cover the entire sky observable by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), spanning approximately 22000 square degrees of declination between −14° and +66°, and in the frequency range of 1050–1450MHz, with the expectation of eventually detecting more than 100000 H i sources. Between August 2020 and June 2023, FASHI had covered more than 7600 square degrees, which is approximately 35% of the total sky observable by FAST. It has a median detection sensitivity of around 0.76 mJy beam−1 and a spectral line velocity resolution of ∼6.4km s−1 at a frequency of ∼1.4GHz. As of now, a total of 41741 extragalactic H i sources have been detected in the frequency range 1305.5–1419.5 MHz, corresponding to a redshift limit of z ≲ 0.09. By cross-matching FASHI sources with the Siena Galaxy Atlas (SGA) and the Sloan Digital Sky Survey (SDSS) catalogs, we found that 16972 (40.7%) sources have spectroscopic redshifts and 10975 (26.3%) sources have only photometric redshifts. Most of the remaining 13794 (33.0%) H i sources are located in the direction of the Galactic plane, making their optical counterparts difficult to identify due to high extinction or high contamination of Galactic stellar sources. Based on current survey results, the FASHI survey is an unprecedented blind extragalactic H i survey. It has higher spectral and spatial resolution and broader coverage than the Arecibo Legacy Fast ALFA Survey (ALFALFA). When completed, FASHI will provide the largest extragalactic H i catalog and an objective view of H i content and large-scale structure in the local universe. [ABSTRACT FROM AUTHOR]

The near-Earth (within ∼100 pc) supernova explosions in the past several million years can cause the global deposition of radioactive elements (e.g., 60Fe) on Earth. The remnants of such supernovae are too old to be easily identified. It is therefore of great interest to search for million-year-old near-Earth neutron stars or black holes, the products of supernovae. However, neutron stars and black holes are challenging to find even in our Solar neighbourhood if they are not radio pulsars or X-ray/γ-ray emitters. Here we report the discovery of one of the nearest (127.7 ± 0.3 pc) neutron star candidates in a detached single-lined spectroscopic binary LAMOST J235456.73+335625.9 (hereafter J2354). Utilizing the time-resolved ground-based spectroscopy and space photometry, we find that J2354 hosts an unseen compact object with Minv being 1.4–1.6 M⊙. The follow-up Swift ultraviolet (UV) and X-ray observations suggest that the UV and X-ray emission is produced by the visible star rather than the compact object. Hence, J2354 probably harbours a neutron star rather than a hot ultramassive white dwarf. Two-hour exceptionally sensitive radio follow-up observations with Five-hundred-meter Aperture Spherical radio Telescope fail to reveal any pulsating radio signals at the 6σ flux upper limit of 12.5 µJy. Therefore, the neutron star candidate in J2354 can only be revealed via our time-resolved observations. Interestingly, the distance between J2354 and our Earth can be as close as ∼ 50 pc around 2.5 million years (Myrs) ago, as revealed by the Gaia kinematics. Our discovery demonstrates a promising way to unveil the hidden near-Earth neutron stars in binaries by exploring the optical time domain, thereby facilitating understanding of the metal-enrichment history in our Solar neighbourhood. [ABSTRACT FROM AUTHOR]

Much of the research in supernova cosmology is based on an assumption that the peak luminosity of type Ia supernovae (SNe Ia), after a standardization process, is independent of the galactic environment. A series of recent studies suggested that there is a significant correlation between the standardized luminosity and the progenitor age of SNe Ia. The correlation found in the most recent work by Lee et al. [Mon. Not. R. Astron. Soc. 517, 2697 (2022)] is strong enough to explain the extra dimming of distant SNe Ia and therefore casts doubts on the direct evidence of cosmic acceleration. The present work incorporates the uncertainties of progenitor ages, which were ignored in Lee et al., into a fully Bayesian inference framework. We find a weaker dependence of supernova standardized luminosity on the progenitor age, but the detection of correlation remains significant (3.5σ). Assuming that such correlation can be extended to high redshift and applying it to the Pantheon SN Ia data set, we confirm that when the Hubble residual does not include intrinsic scatter, the age-bias could be the primary cause of the observed extra dimming of distant SNe Ia. Furthermore, we use the PAge formalism, which is a good approximation to many dark energy and modified gravity models, to do a model comparison. We find that if intrinsic scatter is included in the Hubble residual, the Lambda cold dark matter model remains a good fit. However, in a scenario without intrinsic scatter, the Lambda cold dark matter model faces a challenge. [ABSTRACT FROM AUTHOR]

We present a forecast of the cosmological parameter estimation using fast radio bursts (FRBs) from the upcoming Square Kilometre Array (SKA), focusing on the issues of dark energy, the Hubble constant, and baryon density. We simulate 105 and 106 localized FRBs from a 10-year SKA observation, and find that: (1) using 106 FRB data alone can tightly constrain dark-energy equation of state parameters better than CMB+BAO+SNe, providing an independent cosmological probe to explore dark energy; (2) combining the FRB data with gravitational-wave standard siren data from 10-year observation with the Einstein Telescope, the Hubble constant can be constrained to a sub-percent level, serving as a powerful low-redshift probe; (3) using 106 FRB data can constrain the baryon density Ωbh to a precision of ∼0.1%. Our results indicate that SKA-era FRBs will provide precise cosmological measurements to shed light on both dark energy and the missing baryon problem, and help resolve the Hubble tension. [ABSTRACT FROM AUTHOR]

The Wide Field Survey Telescope (WFST) is a dedicated photometric surveying facility being built jointly by University of Science and Technology of China (USTC) and the Purple Mountain Observatory (PMO). It is equipped with a 2.5-meter diameter primary mirror, an active optics system, and a mosaic CCD camera with 0.73 gigapixels on the primary focal plane for high-quality image capture over a 6.5-square-degree field of view. The installation of WFST near the summit of Saishiteng mountain in the Lenghu region is scheduled in summer of 2023, and the operation is planned to start three months later. WFST will scan the northern sky in four optical bands (u, g, r and i) at cadences from hourly/daily in the deep high-cadence survey (DHS) program, to semi-weekly in the wide field survey (WFS) program. During a photometric night, a nominal 30 s exposure in the WFS program will reach a depth of 22.27, 23.32, 22.84, and 22.31 (AB magnitudes) in these four bands, respectively, allowing for the detection of a tremendous amount of transients in the low-z universe and a systematic investigation of the variability of Galactic and extragalactic objects. In the DHS program, intranight 90 s exposures as deep as 23 (u) and 24 mag (g), in combination with target of opportunity follow-ups, will provide a unique opportunity to explore energetic transients in demand for high sensitivities, including the electromagnetic counterparts of gravitational wave events, supernovae within a few hours of their explosions, tidal disruption events and fast, luminous optical transients even beyond redshift of unity. In addition, the final 6-year co-added images, anticipated to reach g ≃ 25.8 mag in WFS or 1.5 mags deeper in DHS, will be of fundamental importance to general Galactic and extragalactic science. The highly uniform legacy surveys of WFST will serve as an indispensable complement to those of the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) that monitors the southern sky. [ABSTRACT FROM AUTHOR]

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 < z < 0.35) + SKA1-MID (0.35 < z < 0.8) + HIRAX (0.8 < z < 2.5), to measure dark energy. We simulate the 21 cm IM observations under the assumption of excellent foreground removal. We find that the synergy of three experiments could place quite tight constraints on cosmological parameters. For example, it provides σ(Ωm) = 0.0039 and σ(H0) = 0.27 km s−1 Mpc−1 in the ACDM model. Notably, the synergy could break the cosmological parameter degeneracies when constraining the dynamical dark energy models. Concretely, the joint observation offers σ(w) = 0.019 in the wCDM model, and σ(w0) = 0.085 and σ(wa) = 0.32 in the w0waCDM model. These results are better than or equal to those given by CMB+BAO+SN. In addition, when the foreground removal efficiency is relatively low, the strategy still performs well. Therefore, the 21 cm IM joint survey strategy is promising and worth pursuing. [ABSTRACT FROM AUTHOR]

The 2-m aperture Chinese Space Station Telescope (CSST), which observes at wavelengths ranging from 255 to 1000 nm, is expected to start science operations in 2024. An ultra-deep field observation program covering approximately 10 deg2 is proposed with supernovae (SNe) and other transients as one of its primary science drivers. This paper presents the simulated detection results of type Ia supernovae (SNe Ia) and explores the impact of new datasets on the determinations of cosmological parameters. The simulated observations are conducted with an exposure time of 150 s and cadences of 10, 20, and 30 d. The survey mode covering a total of 80 observations but with a random cadence in the range of 4 to 14 d is also explored. Our simulation results indicate that the CSST can detect up to ∼ 1800 SNe Ia at z < 1.3. The simulated SNe Ia are then used to constrain the cosmological parameters. The constraint on Ωm can be improved by 37.5% using the 10-d cadence sample in comparison with the Pantheon sample. A deeper measurement simulation with a 300 s exposure time together with the Pantheon sample improves the current constraints on Ωm by 58.3% and ω by 47.7%. Taking future lager sets of nearby SN Ia sample form ground-based surveys (i.e., N ∼ 3400) into consideration, the constraints on ω can be improved by 59.1%. The CSST ultra-deep field observation program is expected to discover large amounts of SNe Ia over a broad redshift span and enhance our understanding of the nature of dark energy. [ABSTRACT FROM AUTHOR]

In this paper, we analyse the JLA data on Supernova observations in the context of k - essence dark energy model with Lagrangian L = V F (X) , with a constant potential V and the dynamical term X = (1 / 2) ∇ μ ϕ ∇ ν ϕ = ϕ ˙ 2 / 2 for a homogeneous scalar field ϕ (t) , in a flat FRW spacetime background. Scaling relations are used to extract temporal behaviour of different cosmological quantities and the form of the function F(X) from the data. We explore how the parameters of the model, viz. value of the constant potential V and a constant C appearing in the emergent scaling relation, control the dynamics of the model in the context of JLA data, by setting up and analysing an equivalent dynamical system described by a set of autonomous equations. [ABSTRACT FROM AUTHOR]

One of the most prominent challenges to the standard Lambda cold dark matter (ΛCDM) cosmology is the tension between the structure growth parameter S8 constrained by the cosmic microwave background (CMB) data and the smaller one suggested by the cosmic shear data. Recent studies show that, for ΛCDM cosmology, redshift-space distortion (RSD) data also prefers a smaller S8 that is ∼ 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 S8 with the most up-to-date RSD data set where the correlation between data points is 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 ΛCDM cosmology we find S8 = 0.812 ± 0.026, which is ∼ 2σ larger than previous studies, and hence is consistent with the CMB constraint. By replacing ΛCDM 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 S8 is insensitive to the cosmological model. [ABSTRACT FROM AUTHOR]