We investigate the null tests of cosmic accelerated expansion by using the baryon acoustic oscillation(BAO)data measured by the dark energy spectroscopic instrument(DESI)and reconstruct the dimensionless Hubble parame...We investigate the null tests of cosmic accelerated expansion by using the baryon acoustic oscillation(BAO)data measured by the dark energy spectroscopic instrument(DESI)and reconstruct the dimensionless Hubble parameter E(z)from the DESI BAO Alcock-Paczynski(AP)data using Gaussian process to perform the null test.We find strong evidence of accelerated expansion from the DESI BAO AP data.By reconstructing the deceleration parameter q(z) from the DESI BAO AP data,we find that accelerated expansion persisted until z■0.7 with a 99.7%confidence level.Additionally,to provide insights into the Hubble tension problem,we propose combining the reconstructed E(z) with D_(H)/r_(d) data to derive a model-independent result r_(d)h=99.8±3.1 Mpc.This result is consistent with measurements from cosmic microwave background(CMB)anisotropies using the ΛCDM model.We also propose a model-independent method for reconstructing the comoving angular diameter distance D_(M)(z) from the distance modulus μ,using SNe Ia data and combining this result with DESI BAO data of D_(M)/r_(d) to constrain the value of r_(d).We find that the value of r_(d),derived from this model-independent method,is smaller than that obtained from CMB measurements,with a significant discrepancy of at least 4.17σ.All the conclusions drawn in this paper are independent of cosmological models and gravitational theories.展开更多
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
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
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
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
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
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
基金supported in part by the National Key Research and Development Program of China (Grant No.2020YFC2201504)the National Natural Science Foundation of China (Grant Nos.12588101 and 12535002)。
文摘We investigate the null tests of cosmic accelerated expansion by using the baryon acoustic oscillation(BAO)data measured by the dark energy spectroscopic instrument(DESI)and reconstruct the dimensionless Hubble parameter E(z)from the DESI BAO Alcock-Paczynski(AP)data using Gaussian process to perform the null test.We find strong evidence of accelerated expansion from the DESI BAO AP data.By reconstructing the deceleration parameter q(z) from the DESI BAO AP data,we find that accelerated expansion persisted until z■0.7 with a 99.7%confidence level.Additionally,to provide insights into the Hubble tension problem,we propose combining the reconstructed E(z) with D_(H)/r_(d) data to derive a model-independent result r_(d)h=99.8±3.1 Mpc.This result is consistent with measurements from cosmic microwave background(CMB)anisotropies using the ΛCDM model.We also propose a model-independent method for reconstructing the comoving angular diameter distance D_(M)(z) from the distance modulus μ,using SNe Ia data and combining this result with DESI BAO data of D_(M)/r_(d) to constrain the value of r_(d).We find that the value of r_(d),derived from this model-independent method,is smaller than that obtained from CMB measurements,with a significant discrepancy of at least 4.17σ.All the conclusions drawn in this paper are independent of cosmological models and gravitational theories.
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.
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.
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 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 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.
