This study examines the properties of standard cold dark matter(CDM),fuzzy dark matter(FDM),and selfinteracting dark matter(SIDM)haloes by analyzing the rotation curves of selected dwarf galaxies from SPARC and LITTLE...This study examines the properties of standard cold dark matter(CDM),fuzzy dark matter(FDM),and selfinteracting dark matter(SIDM)haloes by analyzing the rotation curves of selected dwarf galaxies from SPARC and LITTLE THINGS in 3D catalogs.Utilizing the Markov Chain Monte Carlo(MCMC)method for model fitting and Bayesian Information Criterion for model comparison,we find that compared to CDM,both FDM and SIDM haloes generally provide better fits to the observed rotation curves.Our findings reveal that the concentration–mass relation derived from the dark matter-only simulations is not followed by concentrations or masses obtained from the rotation curve data.Our analysis highlights a positive correlation between the core sizes of FDM and SIDM haloes and the effective radius of the galaxy,attributable to gravitational couplings between baryonic and dark matter components.Moreover,our exploration of dark matter fractions at characteristic radii indicates considerable diversity in dark matter distributions across dwarf galaxies.Notably,FDM and SIDM exhibit greater diversity than CDM in this respect.展开更多
We present the application of a machine learning based galaxy group finder to real observational data from the Sloan Digital Sky Survey Data Release 13(SDSS DR13).Originally designed and validated using simulated gala...We present the application of a machine learning based galaxy group finder to real observational data from the Sloan Digital Sky Survey Data Release 13(SDSS DR13).Originally designed and validated using simulated galaxy surveys in redshift space,our method utilizes deep neural networks to recognize galaxy groups and assess their respective halo masses.The model comprises three components:a central galaxy identifier,a group mass estimator,and an iterative group finder.Using mock catalogs from the Millennium Simulation,our model attains above 90%completeness and purity for groups covering a wide range of halo masses from~10^(11)to~10^(15)h^(-1)Me.When applied to SDSS DR13,it successfully identifies over 420,000 galaxy groups,displaying a strong agreement in group abundance,redshift distribution,and halo mass distribution with conventional techniques.The precision in identifying member galaxies is also notably high,with more than 80%of groups with lower mass achieving perfect alignments.The model shows strong performance across different magnitude thresholds,making retraining unnecessary.These results confirm the efficiency and adaptability of our methodology,offering a scalable and accurate solution for upcoming large-scale galaxy surveys and studies of cosmological formations.Our SDSS group catalog and the essential observable properties of galaxies are available at https://github.com/Juntao Ma/SDSS-DR13-group-catalog.git.展开更多
本文首先回顾了偏转引力理论和物质粒子的微子云理论,分析了太阳光球层、地球大气层、地球水圈层、地壳岩石层、土星大气层、木星大气层和氦、锂、铍、硼、碳元素为主的物质中引力子的聚集情况,说明由氢氦元素为主的太阳光球层、土星大...本文首先回顾了偏转引力理论和物质粒子的微子云理论,分析了太阳光球层、地球大气层、地球水圈层、地壳岩石层、土星大气层、木星大气层和氦、锂、铍、硼、碳元素为主的物质中引力子的聚集情况,说明由氢氦元素为主的太阳光球层、土星大气层、木星大气层中,引力子聚集可以产生氢元素,同样可以推测在由氢氦元素为主的宇宙星云中,也可以产生氢元素,此结论与天文观测事实相符。最后通过对宇宙中普通物质的占比计算,说明宇宙中绝大多数引力子都转化为氢元素,只有极少数引力子在传播引力。本文的分析提出了一种宇宙中氢元素丰度形成的新过程。This article first reviews the theory of deflected gravity and the micron cloud theory of matter par-ticles, and analyzes the aggregation of gravitons in the solar photosphere, earth’s atmosphere, earth’s hydrosphere, crustal rock layer, atmosphere of Saturn, atmosphere of Jupiter, and materials mainly composed of helium, lithium, beryllium, boron, and carbon elements. This situation shows that in the solar photosphere, the atmosphere of Saturn, and the atmosphere of Jupiter, which are dominated by hydrogen and helium elements, the aggregation of gravitons can produce hydrogen elements. It can also be speculated that in cosmic nebulae dominated by hydrogen and helium ele-ments, hydrogen elements can also be produced. This conclusion is consistent with the astronomical observation facts. Finally, by calculating the proportion of ordinary matter in the universe, it is shown that the vast majority of gravitons in the universe are converted into hydrogen elements, and only a very small number of gravitons are spreading gravity. The analysis in this paper propos-es a new process for the formation of hydrogen abundance in the universe.展开更多
This work aims to investigate the different stability conditions of two scenarios of the inhomogeneous Lemaitre–Tolman–Bond model of the universe with holographic dark energy.We considered the Rényi and Tsallis...This work aims to investigate the different stability conditions of two scenarios of the inhomogeneous Lemaitre–Tolman–Bond model of the universe with holographic dark energy.We considered the Rényi and Tsallis holographic models of interacting dark energy.These holographic models are investigated using the IR cutoff that equals the Hubble horizon.Various stability conditions of these models have been investigated to understand how much these models can tell us about the recent and future epochs of the universe in comparison with the cosmological constant model,orΛCDM model.The conditions of violating the cosmological energy conditions have been studied.The evolution of the entropy and its first and second derivatives have been calculated and plotted for these holographic models.This gives an idea of how far these models satisfy the generalized second law of thermodynamics and hence have thermodynamical stability.The dynamical stability is studied for these evolved models,which give us glimpses of the dynamical stability at different phases of its evolution.We focus on investigating the stability in recent and near future times up to z≤-4.Further investigation of stability has been obtained by studying the evolved sound speed squared parameter for these models,which gave us a final and decisive evaluation of the stability of these models.展开更多
A simple orbit classification constraint extension to stellar dynamical modeling using Schwarzschild’s method is demonstrated.The classification scheme used is the existing“orbit circularity”scheme(λ_(z))where orb...A simple orbit classification constraint extension to stellar dynamical modeling using Schwarzschild’s method is demonstrated.The classification scheme used is the existing“orbit circularity”scheme(λ_(z))where orbits are split into four groups—hot,warm,cold,and counter-rotating orbits.Other schemes which can be related to the orbit weights are expected to be viable as well.The results show that the classification constraint works well in modeling.However,given that orbits in external galaxies are not observable,it is not clear how the orbit classification for any particular galaxy may be determined.Perhaps range constraints for different types of galaxies determined from cosmological simulations may offer a way forward.展开更多
Hydrodynamical cosmological simulations of galaxy formation such as IllustrisTNG or Auriga have shown considerable success in approximately matching many galaxy properties,but their treatment of the star-forming inter...Hydrodynamical cosmological simulations of galaxy formation such as IllustrisTNG or Auriga have shown considerable success in approximately matching many galaxy properties,but their treatment of the star-forming interstellar medium(ISM)has relied on heuristic sub-grid models.However,recent high-resolution simulations of the ISM that directly resolve the regulation of star formation suggest different mean relations for the dependences of pressure and star formation rate on the average gas density.In this study,we adopt such a modern,physically grounded parameterization inspired by the TIGRESS small-scale simulations.We dub this model TEQS and use it for a detailed comparative analysis of the formation and evolution of a Milky Way-sized galaxy when compared with the widely used TNG model.By employing high-resolution simulations in tall box setups,we first investigate the structural differences expected for these two models when applied to different self-gravitating gas surface densities.Our results indicate that TEQS produces considerably thinner gaseous layers and can be expected to form stellar distributions with smaller scale-height than TNG,especially at higher surface density.To test whether this induces systematic structural differences in cosmological galaxy formation simulations,we carry out zoom-in simulations of 12 galaxies taken from the set of Milky Way-sized galaxies that have been studied in the Auriga project.Comparing results for these galaxies shows that disk galaxies formed with the TEQS model have on average very similar stellar mass but are more concentrated in their central regions and exhibit smaller stellar radii compared to those formed with the TNG model.The differences in the scale-heights of the formed stellar disks are only marginal,however,suggesting that other factors for setting the thickness of the disk are more important than the applied ISM equation-of-state model.Overall,the predicted galaxy structure is quite similar for TNG and TEQS despite significant differences in the employed star formation law,demonstrating that feedback processes are more important in regulating the stellar mass than the precise star formation law itself.展开更多
The redshifted 21 cm line,arising from neutral hydrogen,offers a unique probe into the intergalactic medium and the first stars and galaxies formed in the early universe.However,detecting this signal is a challenging ...The redshifted 21 cm line,arising from neutral hydrogen,offers a unique probe into the intergalactic medium and the first stars and galaxies formed in the early universe.However,detecting this signal is a challenging task because of artificial radio-frequency interference(RFI)and systematic errors such as ground effects.The interior of the Antarctic continent provides an excellent location to make such observations,with minimal RFI and relatively stable foreground signals.Moreover,a flat plateau in central Antarctica,with an ice cap over 2000 m deep,will show less ground reflection of radio waves,reducing the signal complexity in the area around the probing antenna.It may be advantageous to perform cosmological 21 cm experiments in Antarctica,and a 21 cm Antarctic global spectrum experiment can potentially be deployed on the Antarctic ice cap.We have performed preliminary instrumental design,system calibration,and implementation of such an instrument optimized for extreme cold and capable of long-term autonomous operation.This system shows the ability to effectively detect the 21 cm signal,confirming Antarctica as an excellent observational site for radio cosmology.展开更多
Using a semi-analytic approach,we estimate halo spins for a large sample of H I-rich galaxies from the Arecibo Legacy Fast ALFA Survey and examine the correlation between H I mass fractions and halo spins.Our analysis...Using a semi-analytic approach,we estimate halo spins for a large sample of H I-rich galaxies from the Arecibo Legacy Fast ALFA Survey and examine the correlation between H I mass fractions and halo spins.Our analysis reveals a strong correlation between halo spin and the H I-to-stellar mass ratio in both low-mass and massive galaxy samples.This finding suggests a universal formation scenario:higher halo spin reduces angular momentum loss and gas condensation,leading to lower star formation rates and weaker feedback,which in turn help retain gas within dark matter halos.展开更多
We present the first high-precision model for the group-scale strong lensing system CASSOWARY 19(CSWA19),utilizing images from the Hubble Space Telescope.Sixteen member galaxies identified via the red-sequence method,...We present the first high-precision model for the group-scale strong lensing system CASSOWARY 19(CSWA19),utilizing images from the Hubble Space Telescope.Sixteen member galaxies identified via the red-sequence method,and the main halo,all modeled as the dual Pseudo Isothermal Elliptical profile,are incorporated into a parametric lens model alongside an external shear field.To model the system,we adopt the PYAUTOLENS software package,employing a progressive search chain strategy for realizing the transition of source model from multiple Sérsic profiles to a brightness-adaptive pixelization,which uses 1000 pixels in the source plane to reconstruct the background source corresponding to 177,144 image pixels in the image plane.Our results indicate that the total mass within the Einstein radius is MθE≈1.41×10^(13)M_(⊙) and the average slope of the total mass density ρ(r)∝r^(−γ) is γ=1.33 within the effective radius.This slope is shallower than those measured in galaxies and groups but is closer to those of galaxy clusters.In addition,our approach successfully resolves the two merging galaxies in the background source and yields a total magnification of μ=-103.18_(-0.19)^(+0.23),which is significantly higher than the outcomes from previous studies of CSWA19.In summary,our research demonstrates the effectiveness of the brightness-adaptive pixelization source reconstruction technique for modeling group-scale strong lensing systems.It can serve as a technical reference for future investigations into pixel-level modeling of the group-and clusterscale strong lensing systems.展开更多
In this paper,cosmic distance duality relation(CDDR)is probed without considering any background cosmological model.The only a priori assumption is that the Universe is described by the Friedmann–Lema?tre–Robertson...In this paper,cosmic distance duality relation(CDDR)is probed without considering any background cosmological model.The only a priori assumption is that the Universe is described by the Friedmann–Lema?tre–Robertson–Walker(FLRW)metric.The strong gravitational lensing data is used to construct the dimensionless comoving distance function d(z)and latest type Ia supernovae Pantheon+data is used to estimate luminosity distances at the corresponding redshifts z.Using the distance sum rule along null geodesics of the FLRW metric,the CDDR violation is probed in both flat and non-flat spacetime by considering two parametrizations forη(z),the function generally used to probe the possible deviations from CDDR.The results show that CDDR is compatible with the observations at a very high level of confidence for linear parametrization in a flat Universe.In a non-flat Universe too,CDDR is valid within the 1σconfidence interval with a mild dependence ofηon the curvature density parameterΩK.The results for nonlinear parametrization also show no significant deviation from CDDR.展开更多
We present constraints on the baryonic matter density parameter,Ωb,within the framework of theΛCDM model.Our analysis utilizes observational data on the effective optical depth from high-redshift quasars.To paramete...We present constraints on the baryonic matter density parameter,Ωb,within the framework of theΛCDM model.Our analysis utilizes observational data on the effective optical depth from high-redshift quasars.To parameterize the photoionization rateΓ-12,we employ a Bézier polynomial.Additionally,we approximate the Hubble parameter at high redshifts as H(z)≈100hΩ_(m)^(1/2)(1+z)^(3/2)kms^(-1)Mpc^(-1).Confidence regions are obtained with h=0.701±0.013 andΩm=0.315,optimized by the Planck mission.The best-fit values are andΩb=0.043_(0.006/^(+0.005))andΩb=0.045_(0.006)/^(+0.004),corresponding to an old data set and a new data set,respectively.We test the non-parametric form ofΓ-12,obtainingΩb=0.048_(-0.003)/^(+0.001).These results are consistent with the findings of Planck at the 1σcon?dence level.Our findings underscore the effectiveness of quasar data sets in constrainingΩb,eliminating the need for independent photoionization rate data.This approach provides detailed cosmic information about baryon density and the photoionization history of the intergalactic medium.展开更多
This paper aims to develop non-interacting ghost dark energy and generalized ghost dark energy models within the framework of f(Q)theory using the correspondence scheme.We use pressureless matter and a power-law scale...This paper aims to develop non-interacting ghost dark energy and generalized ghost dark energy models within the framework of f(Q)theory using the correspondence scheme.We use pressureless matter and a power-law scale factor.The cosmic implications of the resulting models are studied through the equation of state parameter and the phase planes.We also check the stability of the reconstructed models through the squared speed of sound parameter.The equation of state parameter exhibits a phantom era,the(ωD-ω'D)-plane indicates a freezing region,while the(r-s)-plane corresponds to the Chaplygin gas model for both models.It is also found that only the generalized ghost dark energy model remains stable throughout cosmic evolution.We conclude that our findings align well with current observational data.展开更多
In this study,we used thef(T) gravity framework with the energy-momentum tensor for a perfect fluid to derive key cosmological parameters,including the Hubble parameter H,deceleration parameter q and Statefinder diagn...In this study,we used thef(T) gravity framework with the energy-momentum tensor for a perfect fluid to derive key cosmological parameters,including the Hubble parameter H,deceleration parameter q and Statefinder diagnostics.Model parameters were optimized using an R^(2) test,resulting in β=1.312_(-0.014)^(+0.013),ξ=1.273_(-0.0071)^(+0.0065) and H_(0)=72.60_(-0.49)^(+0.50),with an R^(2) of 0.9527.Our model aligns closely with the ACDM model and shows good performance based on AIC and BIC criteria.Analyzing the q(z) curve revealed the transition from deceleration to acceleration in the universe's expansion.Additionally,we examined pressure,energy density,and equation of state parameter for two models,f(T)=λT and f(T)=T+βT^(2),both aligning well with observational data.The r-s and r-q diagnostics further confirm our model's consistency with ΛCDM,making it a strong alternative for explaining cosmic expansion.The evolution of Ω(z) shows strong consistency with the ΛCDM model,with the Om parameter approaching 0.3 at lower redshifts and parameter uncertainties highlighting the model's reliability.展开更多
While cold dark matter is widely supported by a range of cosmological observations,it encounters several difficulties at smaller scales.These issues have prompted the investigation of various alternative dark matter c...While cold dark matter is widely supported by a range of cosmological observations,it encounters several difficulties at smaller scales.These issues have prompted the investigation of various alternative dark matter candidates,leaving the question“What is dark matter?”still open.In this work,we propose a new cosmological model that considers dark matter as a barotropic fluid with a constant equation of state parameter and interprets dark energy as the phenomenological emergent dark energy rather than a cosmological constant.We then place constraints on our new model using the Planck 2018 Cosmic Microwave Background(CMB)anisotropy measurements,Baryon Acoustic Oscillation measurements from the Dark Energy Spectroscopic Instrument(DESI),the Pantheon Plus(PP)compilation of Type Ia supernovae,and the Redshift Space Distortions(RSD)data from Gold 2018.The results show statistically significant signal for positive dark matter equation of state and square of sound speed w_(dm)=c_(s,dm)^(2)(10^(7) w_(dm)=4.0_(-2.3)^(+2.5)at the 95%confidence level)for the data combination CMB+DESI+PP+RSD.However,Bayesian evidence indicates that this data combination favors theΛCDM model with very strong evidence.展开更多
基金financially supporting this research through PPMI KK 2024 Program,contract number 616BO/IT1.C02/KU/2024。
文摘This study examines the properties of standard cold dark matter(CDM),fuzzy dark matter(FDM),and selfinteracting dark matter(SIDM)haloes by analyzing the rotation curves of selected dwarf galaxies from SPARC and LITTLE THINGS in 3D catalogs.Utilizing the Markov Chain Monte Carlo(MCMC)method for model fitting and Bayesian Information Criterion for model comparison,we find that compared to CDM,both FDM and SIDM haloes generally provide better fits to the observed rotation curves.Our findings reveal that the concentration–mass relation derived from the dark matter-only simulations is not followed by concentrations or masses obtained from the rotation curve data.Our analysis highlights a positive correlation between the core sizes of FDM and SIDM haloes and the effective radius of the galaxy,attributable to gravitational couplings between baryonic and dark matter components.Moreover,our exploration of dark matter fractions at characteristic radii indicates considerable diversity in dark matter distributions across dwarf galaxies.Notably,FDM and SIDM exhibit greater diversity than CDM in this respect.
基金supported by the National Key R&D Program of China(2022YFA1602901)the National Natural Science Foundation of China(NSFC,grant Nos.11988101,11873051,12125302,and 11903043)+2 种基金CAS Project for Young Scientists in Basic Research(grant No.YSBR-062)the China Manned Space Program(grant Nos.CMS-CSST2025-A03 and CMS-CSST-2025-A10)the K.C.Wong Education Foundation。
文摘We present the application of a machine learning based galaxy group finder to real observational data from the Sloan Digital Sky Survey Data Release 13(SDSS DR13).Originally designed and validated using simulated galaxy surveys in redshift space,our method utilizes deep neural networks to recognize galaxy groups and assess their respective halo masses.The model comprises three components:a central galaxy identifier,a group mass estimator,and an iterative group finder.Using mock catalogs from the Millennium Simulation,our model attains above 90%completeness and purity for groups covering a wide range of halo masses from~10^(11)to~10^(15)h^(-1)Me.When applied to SDSS DR13,it successfully identifies over 420,000 galaxy groups,displaying a strong agreement in group abundance,redshift distribution,and halo mass distribution with conventional techniques.The precision in identifying member galaxies is also notably high,with more than 80%of groups with lower mass achieving perfect alignments.The model shows strong performance across different magnitude thresholds,making retraining unnecessary.These results confirm the efficiency and adaptability of our methodology,offering a scalable and accurate solution for upcoming large-scale galaxy surveys and studies of cosmological formations.Our SDSS group catalog and the essential observable properties of galaxies are available at https://github.com/Juntao Ma/SDSS-DR13-group-catalog.git.
文摘本文首先回顾了偏转引力理论和物质粒子的微子云理论,分析了太阳光球层、地球大气层、地球水圈层、地壳岩石层、土星大气层、木星大气层和氦、锂、铍、硼、碳元素为主的物质中引力子的聚集情况,说明由氢氦元素为主的太阳光球层、土星大气层、木星大气层中,引力子聚集可以产生氢元素,同样可以推测在由氢氦元素为主的宇宙星云中,也可以产生氢元素,此结论与天文观测事实相符。最后通过对宇宙中普通物质的占比计算,说明宇宙中绝大多数引力子都转化为氢元素,只有极少数引力子在传播引力。本文的分析提出了一种宇宙中氢元素丰度形成的新过程。This article first reviews the theory of deflected gravity and the micron cloud theory of matter par-ticles, and analyzes the aggregation of gravitons in the solar photosphere, earth’s atmosphere, earth’s hydrosphere, crustal rock layer, atmosphere of Saturn, atmosphere of Jupiter, and materials mainly composed of helium, lithium, beryllium, boron, and carbon elements. This situation shows that in the solar photosphere, the atmosphere of Saturn, and the atmosphere of Jupiter, which are dominated by hydrogen and helium elements, the aggregation of gravitons can produce hydrogen elements. It can also be speculated that in cosmic nebulae dominated by hydrogen and helium ele-ments, hydrogen elements can also be produced. This conclusion is consistent with the astronomical observation facts. Finally, by calculating the proportion of ordinary matter in the universe, it is shown that the vast majority of gravitons in the universe are converted into hydrogen elements, and only a very small number of gravitons are spreading gravity. The analysis in this paper propos-es a new process for the formation of hydrogen abundance in the universe.
文摘This work aims to investigate the different stability conditions of two scenarios of the inhomogeneous Lemaitre–Tolman–Bond model of the universe with holographic dark energy.We considered the Rényi and Tsallis holographic models of interacting dark energy.These holographic models are investigated using the IR cutoff that equals the Hubble horizon.Various stability conditions of these models have been investigated to understand how much these models can tell us about the recent and future epochs of the universe in comparison with the cosmological constant model,orΛCDM model.The conditions of violating the cosmological energy conditions have been studied.The evolution of the entropy and its first and second derivatives have been calculated and plotted for these holographic models.This gives an idea of how far these models satisfy the generalized second law of thermodynamics and hence have thermodynamical stability.The dynamical stability is studied for these evolved models,which give us glimpses of the dynamical stability at different phases of its evolution.We focus on investigating the stability in recent and near future times up to z≤-4.Further investigation of stability has been obtained by studying the evolved sound speed squared parameter for these models,which gave us a final and decisive evaluation of the stability of these models.
基金supported by the National Key Basic Research and Development Program of China(No.2018YFA0404501 to Shude Mao)by the National Natural Science Foundation of China(NSFC,grant Nos.11821303,11761131004 and 11761141012 to Shude Mao).
文摘A simple orbit classification constraint extension to stellar dynamical modeling using Schwarzschild’s method is demonstrated.The classification scheme used is the existing“orbit circularity”scheme(λ_(z))where orbits are split into four groups—hot,warm,cold,and counter-rotating orbits.Other schemes which can be related to the orbit weights are expected to be viable as well.The results show that the classification constraint works well in modeling.However,given that orbits in external galaxies are not observable,it is not clear how the orbit classification for any particular galaxy may be determined.Perhaps range constraints for different types of galaxies determined from cosmological simulations may offer a way forward.
基金supported by the National SKA Program of China(grant No.2020SKA0110100)the CAS Project for Young Scientists in Basic Research (No.YSBR-092)the science research grants from the China Manned Space Project with Nos.CMS-CSST-2021-A02 and GHfund C(202407031909)
文摘Hydrodynamical cosmological simulations of galaxy formation such as IllustrisTNG or Auriga have shown considerable success in approximately matching many galaxy properties,but their treatment of the star-forming interstellar medium(ISM)has relied on heuristic sub-grid models.However,recent high-resolution simulations of the ISM that directly resolve the regulation of star formation suggest different mean relations for the dependences of pressure and star formation rate on the average gas density.In this study,we adopt such a modern,physically grounded parameterization inspired by the TIGRESS small-scale simulations.We dub this model TEQS and use it for a detailed comparative analysis of the formation and evolution of a Milky Way-sized galaxy when compared with the widely used TNG model.By employing high-resolution simulations in tall box setups,we first investigate the structural differences expected for these two models when applied to different self-gravitating gas surface densities.Our results indicate that TEQS produces considerably thinner gaseous layers and can be expected to form stellar distributions with smaller scale-height than TNG,especially at higher surface density.To test whether this induces systematic structural differences in cosmological galaxy formation simulations,we carry out zoom-in simulations of 12 galaxies taken from the set of Milky Way-sized galaxies that have been studied in the Auriga project.Comparing results for these galaxies shows that disk galaxies formed with the TEQS model have on average very similar stellar mass but are more concentrated in their central regions and exhibit smaller stellar radii compared to those formed with the TNG model.The differences in the scale-heights of the formed stellar disks are only marginal,however,suggesting that other factors for setting the thickness of the disk are more important than the applied ISM equation-of-state model.Overall,the predicted galaxy structure is quite similar for TNG and TEQS despite significant differences in the employed star formation law,demonstrating that feedback processes are more important in regulating the stellar mass than the precise star formation law itself.
基金supported by the Polar Research Institute of China and the Chinese Arctic and Antarctic Administrationsupported by the Chinese Academy of Science Key Instrument(ZDKYYQ20200008)the National Natural Science Foundation of China(12473094 and 12273070).
文摘The redshifted 21 cm line,arising from neutral hydrogen,offers a unique probe into the intergalactic medium and the first stars and galaxies formed in the early universe.However,detecting this signal is a challenging task because of artificial radio-frequency interference(RFI)and systematic errors such as ground effects.The interior of the Antarctic continent provides an excellent location to make such observations,with minimal RFI and relatively stable foreground signals.Moreover,a flat plateau in central Antarctica,with an ice cap over 2000 m deep,will show less ground reflection of radio waves,reducing the signal complexity in the area around the probing antenna.It may be advantageous to perform cosmological 21 cm experiments in Antarctica,and a 21 cm Antarctic global spectrum experiment can potentially be deployed on the Antarctic ice cap.We have performed preliminary instrumental design,system calibration,and implementation of such an instrument optimized for extreme cold and capable of long-term autonomous operation.This system shows the ability to effectively detect the 21 cm signal,confirming Antarctica as an excellent observational site for radio cosmology.
基金support from the National Natural Science Foundation of China(NSFC)grant 12273037the CAS Pioneer Hundred Talents Program(Category B)+1 种基金the USTC Research Funds of the Double First-Class Initiativesupported by the China Manned Space Program with grant No.CMS-CSST-2025-A06 and CMS-CSST-2025-A08.
文摘Using a semi-analytic approach,we estimate halo spins for a large sample of H I-rich galaxies from the Arecibo Legacy Fast ALFA Survey and examine the correlation between H I mass fractions and halo spins.Our analysis reveals a strong correlation between halo spin and the H I-to-stellar mass ratio in both low-mass and massive galaxy samples.This finding suggests a universal formation scenario:higher halo spin reduces angular momentum loss and gas condensation,leading to lower star formation rates and weaker feedback,which in turn help retain gas within dark matter halos.
基金supported by the National Key Research and Development Program of China(Nos.2023YFB3002501 and 2022YFA1602903)the China Manned Space Project(No.CMS-CSST-2021-A01)+1 种基金the National Natural Science Foundation of China(Nos.12473002 and 11988101)L.W.acknowledges the support from the GHfund A(Nos.202302017475 and 202407017555).
文摘We present the first high-precision model for the group-scale strong lensing system CASSOWARY 19(CSWA19),utilizing images from the Hubble Space Telescope.Sixteen member galaxies identified via the red-sequence method,and the main halo,all modeled as the dual Pseudo Isothermal Elliptical profile,are incorporated into a parametric lens model alongside an external shear field.To model the system,we adopt the PYAUTOLENS software package,employing a progressive search chain strategy for realizing the transition of source model from multiple Sérsic profiles to a brightness-adaptive pixelization,which uses 1000 pixels in the source plane to reconstruct the background source corresponding to 177,144 image pixels in the image plane.Our results indicate that the total mass within the Einstein radius is MθE≈1.41×10^(13)M_(⊙) and the average slope of the total mass density ρ(r)∝r^(−γ) is γ=1.33 within the effective radius.This slope is shallower than those measured in galaxies and groups but is closer to those of galaxy clusters.In addition,our approach successfully resolves the two merging galaxies in the background source and yields a total magnification of μ=-103.18_(-0.19)^(+0.23),which is significantly higher than the outcomes from previous studies of CSWA19.In summary,our research demonstrates the effectiveness of the brightness-adaptive pixelization source reconstruction technique for modeling group-scale strong lensing systems.It can serve as a technical reference for future investigations into pixel-level modeling of the group-and clusterscale strong lensing systems.
文摘In this paper,cosmic distance duality relation(CDDR)is probed without considering any background cosmological model.The only a priori assumption is that the Universe is described by the Friedmann–Lema?tre–Robertson–Walker(FLRW)metric.The strong gravitational lensing data is used to construct the dimensionless comoving distance function d(z)and latest type Ia supernovae Pantheon+data is used to estimate luminosity distances at the corresponding redshifts z.Using the distance sum rule along null geodesics of the FLRW metric,the CDDR violation is probed in both flat and non-flat spacetime by considering two parametrizations forη(z),the function generally used to probe the possible deviations from CDDR.The results show that CDDR is compatible with the observations at a very high level of confidence for linear parametrization in a flat Universe.In a non-flat Universe too,CDDR is valid within the 1σconfidence interval with a mild dependence ofηon the curvature density parameterΩK.The results for nonlinear parametrization also show no significant deviation from CDDR.
基金supported by the National SKA Program of China(2022SKA0110202)China Manned Space Program through its Space Application System。
文摘We present constraints on the baryonic matter density parameter,Ωb,within the framework of theΛCDM model.Our analysis utilizes observational data on the effective optical depth from high-redshift quasars.To parameterize the photoionization rateΓ-12,we employ a Bézier polynomial.Additionally,we approximate the Hubble parameter at high redshifts as H(z)≈100hΩ_(m)^(1/2)(1+z)^(3/2)kms^(-1)Mpc^(-1).Confidence regions are obtained with h=0.701±0.013 andΩm=0.315,optimized by the Planck mission.The best-fit values are andΩb=0.043_(0.006/^(+0.005))andΩb=0.045_(0.006)/^(+0.004),corresponding to an old data set and a new data set,respectively.We test the non-parametric form ofΓ-12,obtainingΩb=0.048_(-0.003)/^(+0.001).These results are consistent with the findings of Planck at the 1σcon?dence level.Our findings underscore the effectiveness of quasar data sets in constrainingΩb,eliminating the need for independent photoionization rate data.This approach provides detailed cosmic information about baryon density and the photoionization history of the intergalactic medium.
文摘This paper aims to develop non-interacting ghost dark energy and generalized ghost dark energy models within the framework of f(Q)theory using the correspondence scheme.We use pressureless matter and a power-law scale factor.The cosmic implications of the resulting models are studied through the equation of state parameter and the phase planes.We also check the stability of the reconstructed models through the squared speed of sound parameter.The equation of state parameter exhibits a phantom era,the(ωD-ω'D)-plane indicates a freezing region,while the(r-s)-plane corresponds to the Chaplygin gas model for both models.It is also found that only the generalized ghost dark energy model remains stable throughout cosmic evolution.We conclude that our findings align well with current observational data.
文摘In this study,we used thef(T) gravity framework with the energy-momentum tensor for a perfect fluid to derive key cosmological parameters,including the Hubble parameter H,deceleration parameter q and Statefinder diagnostics.Model parameters were optimized using an R^(2) test,resulting in β=1.312_(-0.014)^(+0.013),ξ=1.273_(-0.0071)^(+0.0065) and H_(0)=72.60_(-0.49)^(+0.50),with an R^(2) of 0.9527.Our model aligns closely with the ACDM model and shows good performance based on AIC and BIC criteria.Analyzing the q(z) curve revealed the transition from deceleration to acceleration in the universe's expansion.Additionally,we examined pressure,energy density,and equation of state parameter for two models,f(T)=λT and f(T)=T+βT^(2),both aligning well with observational data.The r-s and r-q diagnostics further confirm our model's consistency with ΛCDM,making it a strong alternative for explaining cosmic expansion.The evolution of Ω(z) shows strong consistency with the ΛCDM model,with the Om parameter approaching 0.3 at lower redshifts and parameter uncertainties highlighting the model's reliability.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(grant No.2024A1515012573)National key R&D Program of China(grant No.2020YFC2201600)+1 种基金National Natural Science Foundation of China(NSFC,grant No.12073088)National SKA Program of China(grant No.2020SKA0110402)。
文摘While cold dark matter is widely supported by a range of cosmological observations,it encounters several difficulties at smaller scales.These issues have prompted the investigation of various alternative dark matter candidates,leaving the question“What is dark matter?”still open.In this work,we propose a new cosmological model that considers dark matter as a barotropic fluid with a constant equation of state parameter and interprets dark energy as the phenomenological emergent dark energy rather than a cosmological constant.We then place constraints on our new model using the Planck 2018 Cosmic Microwave Background(CMB)anisotropy measurements,Baryon Acoustic Oscillation measurements from the Dark Energy Spectroscopic Instrument(DESI),the Pantheon Plus(PP)compilation of Type Ia supernovae,and the Redshift Space Distortions(RSD)data from Gold 2018.The results show statistically significant signal for positive dark matter equation of state and square of sound speed w_(dm)=c_(s,dm)^(2)(10^(7) w_(dm)=4.0_(-2.3)^(+2.5)at the 95%confidence level)for the data combination CMB+DESI+PP+RSD.However,Bayesian evidence indicates that this data combination favors theΛCDM model with very strong evidence.
