We identify new strong lensing clusters of galaxies from the Sloan Digital Sky Survey Ⅲ （SDSS DR8） by visually inspecting color images of a large sample of clusters of galaxies. We find 68 new clusters showing gian...We identify new strong lensing clusters of galaxies from the Sloan Digital Sky Survey Ⅲ （SDSS DR8） by visually inspecting color images of a large sample of clusters of galaxies. We find 68 new clusters showing giant arcs in addition to 30 known lensing systems. Among 68 cases, 13 clusters are ＂almost certain＂ lensing systems with tangential giant arcs, 22 clusters are ＂probable＂ and 31 clusters are ＂pos- sible＂ lensing systems. We also find two exotic systems with blue rings. The giant arcs have angular separations of 2.0jj - 25.7j~ from the bright central galaxies. We note that the rich clusters are more likely to be lensing systems and the separations between the arcs and the central galaxies increase with cluster richness.展开更多
A spatial orientation of angular momentum vectors of galaxies in six dynamically unstable Abell clusters（S1171, S0001, A1035, A1373, A1474 and A4053） is studied. For this, twodimensional observed parameters（e.g., p...A spatial orientation of angular momentum vectors of galaxies in six dynamically unstable Abell clusters（S1171, S0001, A1035, A1373, A1474 and A4053） is studied. For this, twodimensional observed parameters（e.g., positions, diameters and position angles） are converted into three-dimensional（3D） rotation axes of the galaxy using the ＇position angle-inclination＇ method. The expected isotropic distribution curves for angular momentum vectors are obtained by performing random simulations. The observed and expected distributions are compared using several statistical tests.No preferred alignments of angular momentum vectors of galaxies are noticed in all six dynamically unstable clusters, supporting the hierarchy model of galaxy formation. These clusters have a larger value of velocity dispersion. However, local effects are noticed in the clusters that have substructures in the1D-3D number density maps.展开更多
Clusters of galaxies are the most massive objects in the Universe and precise knowledge of their mass structure is important to understand the history of structure formation and constrain still unknown types of dark c...Clusters of galaxies are the most massive objects in the Universe and precise knowledge of their mass structure is important to understand the history of structure formation and constrain still unknown types of dark contents of the Universe. X-ray spectroscopy of galaxy clusters provides rich information about the physical state of hot intracluster gas and the underlying potential structure. In this paper, starting from the basic description of clusters under equilibrium conditions, we review properties of clusters revealed primarily through X-ray observations considering their thermal and dynamical evolutions. The future prospects of cluster studies using upcoming X-ray missions are also mentioned.展开更多
This paper develops an original theory of dark matter in the current ΛCDM framework, whose main hypothesis is that DM is generated by the own gravitational field, according to an unknown quantum gravitational phenome...This paper develops an original theory of dark matter in the current ΛCDM framework, whose main hypothesis is that DM is generated by the own gravitational field, according to an unknown quantum gravitational phenomenon. This work is the best version of the theory, which I have been developing and publishing since 2014. The hypothesis of DM by quantum gravitation, DMbQG hereafter, has two main consequences: the first one is that the law of DM generation has to be the same, in the halo region, for all the galaxies and the second one is that the haloes are unbounded, so the total DM goes up without limit as the gravitational field is unbounded as well. The first one consequence is backed by the fact that M31 and MW has a fitted function with the same power exponent for the rotation curve at the halo region and both giant galaxies are the only ones whose rotation curves at the halo region may be studied with accuracy. This paper is firstly developed all the theory with M31 rotation curve data up to Chapter 9. The most important formula of the theory is the called Direct mass, which calculates the total mass at a specific radius into the halo region. Chapter 10 is dedicated to apply the theory to Milky Way, it is calculated its total mass at different radius into the halo and such results have been validated successfully using the data of masses at different radius published by two researcher teams. In Chapter 11, it is calculated the direct mass for the Local Group, and it is shown how the DMbQG theory is able to calculate the total mass at 770 kpc, that the dynamical methods estimate to be 5×1012MΘ. In Chapter 12, it is shown a method to estimate the Direct mass formula for a cluster of galaxies, using only its virial mass and virial radius. By this method, it is estimated the parameter a2 of the Local Group, which match with the one calculated in previous chapter by a different method. Also are calculated the parameters a2 associated to Virgo and Coma clusters. In Chapter 13, it is demonstrated how the DE is able to counterbalance the DM at cluster scale, as the Direct mass grows up with the square root of radius whereas the DE grows up with the cubic power. The chapter is an introduction to the DMbQG theory for cluster of galaxies, which has been developed fully by the author in other works. This theory aims to be a powerful method to study DM in the halo region of galaxies and cluster of galaxies and conversely the measures in galaxies and clusters offer the possibility to validate the theory.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
Leveraging the semi-analytic method,we compute halo spins for a substantial sample of H I-bearing galaxies observed in the Arecibo Legacy Fast ALFA Survey.Our statistical analysis reveals a correlation between halo sp...Leveraging the semi-analytic method,we compute halo spins for a substantial sample of H I-bearing galaxies observed in the Arecibo Legacy Fast ALFA Survey.Our statistical analysis reveals a correlation between halo spin and environment,although the trend is subtle.On average,galaxies exhibit a decreasing halo spin tendency in denser environments.This observation contrasts with previous results from N-body simulations in the Lambda Cold Dark Matter framework.The discrepancy may be attributed to environmental gas stripping,leading to an underestimation of halo spins in galaxies in denser environments,or to baryonic processes that significantly alter the original dark matter halo spins,deviating from previous N-body simulation findings.展开更多
The 11th data release of the LAMOST survey provides fundamental stellar parameters but lacks detailed abundance measurements forα-elements,which are crucial for understanding stellar populations and Galactic chemical...The 11th data release of the LAMOST survey provides fundamental stellar parameters but lacks detailed abundance measurements forα-elements,which are crucial for understanding stellar populations and Galactic chemical evolution.In this study,we derive the abundances of oxygen(O),magnesium(Mg),silicon(Si),calcium(Ca),and titanium(Ti)for over 6.8 million stars using LAMOST DR11 low-resolution spectra.To ensure reliable measurements,we select 760 open clusters spanning a broad range of ages and apply Monte Carlo sampling for accurate abundance estimates.Additionally,we utilize over 30,000 stars from the GALAH DR4 catalog to train an XGBoost model for extractingα-element abundances from LAMOST DR11 spectra.Bayesian linear regression is employed to analyze the compositional distribution across the Galactic disk and infer chemical gradients as a function of Galactocentric distance.Our results indicate a general increase in chemical abundances with Galactocentric distance,with oxygen showing the steepest gradient.Our results confirm the overall increase ofα-element abundances with Galactocentric distance,consistent with previous studies,while minor discrepancies in Mg,Ca,and Ti gradients likely arise from differences in sample selection,observational sensitivity,or Galactic enrichment processes.展开更多
Previous X-ray and optical studies of the galaxy cluster pair A222/223 suggested the possible presence of a=lamentary structure connecting the two clusters,a result that appears to be supported by subsequent weak-lens...Previous X-ray and optical studies of the galaxy cluster pair A222/223 suggested the possible presence of a=lamentary structure connecting the two clusters,a result that appears to be supported by subsequent weak-lensing analyses.This=lament has been reported to host a primordial warm-hot intergalactic medium,which existed prior to being heated by the interactions of the clusters.In this study,we made an attempt to examine the reported emission feature with data from an archival Suzaku observation,taking advantage of its low detector background.Because the emission is expected to be very weak,we=rst carefully examined all potential sources of“contamination,”and then modeled the residual emission.Due to large uncertainties,unfortunately,our results can neither con=rm the presence of the reported emission feature nor rule it out.We discuss the sources of uncertainties.展开更多
Web data extraction has become a key technology for extracting valuable data from websites.At present,most extraction methods based on rule learning,visual pattern or tree matching have limited performance on complex ...Web data extraction has become a key technology for extracting valuable data from websites.At present,most extraction methods based on rule learning,visual pattern or tree matching have limited performance on complex web pages.Through ana-lyzing various statistical characteristics of HTML el-ements in web documents,this paper proposes,based on statistical features,an unsupervised web data ex-traction method—traversing the HTML DOM parse tree at first,calculating and generating the statistical matrix of the elements,and then locating data records by clustering method and heuristic rules that reveal in-herent links between the visual characteristics of the data recording areas and the statistical characteristics of the HTML nodes—which is both suitable for data records extraction of single-page and multi-pages,and it has strong generality and needs no training.The ex-periments show that the accuracy and efficiency of this method are equally better than the current data extrac-tion method.展开更多
To realize dynamic statistical publishing and protection of location-based data privacy,this paper proposes a differential privacy publishing algorithm based on adaptive sampling and grid clustering and adjustment.The...To realize dynamic statistical publishing and protection of location-based data privacy,this paper proposes a differential privacy publishing algorithm based on adaptive sampling and grid clustering and adjustment.The PID control strategy is combined with the difference in data variation to realize the dynamic adjustment of the data publishing intervals.The spatial-temporal correlations of the adjacent snapshots are utilized to design the grid clustering and adjustment algorithm,which facilitates saving the execution time of the publishing process.The budget distribution and budget absorption strategies are improved to form the sliding window-based differential privacy statistical publishing algorithm,which realizes continuous statistical publishing and privacy protection and improves the accuracy of published data.Experiments and analysis on large datasets of actual locations show that the privacy protection algorithm proposed in this paper is superior to other existing algorithms in terms of the accuracy of adaptive sampling time,the availability of published data,and the execution efficiency of data publishing methods.展开更多
As part of the LAMOST medium-resolution spectroscopic survey,the LAMOST-MRS-O is a non-time domain survey that aims to perform medium-resolution spectral observations for member stars in the open cluster areas.This su...As part of the LAMOST medium-resolution spectroscopic survey,the LAMOST-MRS-O is a non-time domain survey that aims to perform medium-resolution spectral observations for member stars in the open cluster areas.This survey plans to obtain the spectroscopic parameters such as radial velocity and metal abundances of member stars and provide data support for further study on the chemical and dynamical characteristics and evolution of open clusters in combination with Gaia data.We have completed the observations on ten open cluster fields and obtained 235184 medium-resolution spectra of 133792 stars.Based on the data analyzed of LAMOST DR11v1.1,for some clusters of particular concern,it is found that the sampling ratio of members stars with Gmag<15 mag can reach 70%,which indicates that the LAMOST-MRS-O has reached our initial design goal.展开更多
In the study of spiral galaxy morphology,spiral arm structures are valuable for intuitively reflecting active physical and chemical processes within galaxies.However,long-term scarcity of high-quality one-,three-,and ...In the study of spiral galaxy morphology,spiral arm structures are valuable for intuitively reflecting active physical and chemical processes within galaxies.However,long-term scarcity of high-quality one-,three-,and four-armed galaxy samples has limited deep learning model performance.To address this,this study developed a spiral galaxy data simulation program with a three-stage workflow:first,screening highly reliable training samples;second,selecting the best-performing Imagen architecture as the generative model after comparing nine mainstream ones;finally,training Imagen to generate an open data set of 9402 one-/three-armed galaxies,expanding the original sample size by 6 times.Multi-dimensional evaluations verified reliability and usability:Fréchet Inception Distance scores for N=1 and N=3 tasks were 6.05 and 9.13;the t-distributed Stochastic Neighbor Embedding showed generated data covered and expanded real data distribution;the Structural Similarity Index Measure confirmed no sample duplication.In downstream validation,data augmentation improved seven classification models'average accuracy by 8.7%(DenseNet peaked at 97%),and SHapley Additive exPlanations analysis showed model decisions focused on spiral arm topology.In conclusion,the program and data set support spiral galaxy morphology deep learning research and are publicly available at https://github.com/TuAstroAILab/AstroGS.展开更多
Recent studies have increasingly identified extended main sequence turn-off(e MSTO)phenomena in Galactic open clusters,yet the number of such clusters with sufficient spectroscopic information for member stars remains...Recent studies have increasingly identified extended main sequence turn-off(e MSTO)phenomena in Galactic open clusters,yet the number of such clusters with sufficient spectroscopic information for member stars remains limited.Unlike most studies that rely on fitting isochrones based on color–magnitude diagram(CMD)morphology to account for varying rotational velocities,our approach leverages LAMOST spectral data to compute actual rotational velocity distributions for confirmed cluster members,along with parameters such as metallicity,differential extinction,and rotational inclination,to utilize PARSEC isochrones for fitting the cluster CMDs.We systematically surveyed all known Galactic open clusters and selected 12 clusters where rotational velocity distributions could be reliably calculated for detailed fitting.Our results successfully reproduced the eMSTO phenomenon observed in these clusters.For the majority of clusters,considering only differential extinction and variations in rotational velocity adequately explains the position and morphology of the MSTO.For some intermediate-age clusters,incorporating rotational inclination additionally accounts for the broadening of the MSTO.This study underscores the importance of spectroscopic data in understanding eMSTO phenomena and provides a probable explanation for interpreting the combined effects of differential extinction,rotation,and inclination on the CMDs of Galactic open clusters.展开更多
As large-scale astronomical surveys,such as the Sloan Digital Sky Survey(SDSS)and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST),generate increasingly complex datasets,clustering algorithms have...As large-scale astronomical surveys,such as the Sloan Digital Sky Survey(SDSS)and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST),generate increasingly complex datasets,clustering algorithms have become vital for identifying patterns and classifying celestial objects.This paper systematically investigates the application of five main categories of clustering techniques-partition-based,density-based,model-based,hierarchical,and“others”-across a range of astronomical research over the past decade.This review focuses on the six key application areas of stellar classification,galaxy structure analysis,detection of galactic and interstellar features,highenergy astrophysics,exoplanet studies,and anomaly detection.This paper provides an in-depth analysis of the performance and results of each method,considering their respective suitabilities for different data types.Additionally,it presents clustering algorithm selection strategies based on the characteristics of the spectroscopic data being analyzed.We highlight challenges such as handling large datasets,the need for more efficient computational tools,and the lack of labeled data.We also underscore the potential of unsupervised and semi-supervised clustering approaches to overcome these challenges,offering insight into their practical applications,performance,and results in astronomical research.展开更多
Making use of the 2MASS Data Release, we have searched for nearinfrared （JHK） counterparts to 268 blazars from Donato et al. and obtained 238 counterparts within 5＇＇ in the area covered by 2MASS. It provides us a ...Making use of the 2MASS Data Release, we have searched for nearinfrared （JHK） counterparts to 268 blazars from Donato et al. and obtained 238 counterparts within 5＇＇ in the area covered by 2MASS. It provides us a sample with infrared data several times larger than the previous one of the same kind. Based on our sample and the sample by Donato et al., we have compared in detail the properties of HBLs, LBLs and FSRQs from five aspects and found that HBLs are significantly different from LBLs and FSRQs while LBLs are not obviously different from FSRQs. Our results strongly support the division of BL Lac objects into the high-frequency peaked （HBL） and low-frequency peaked （LBL） objects introduced by Padovani ＆ Giommi and show that HBLs and LBLs are two kinds of blazar having different physical properties.展开更多
We report the discovery of 4 strong gravitational lensing systems by visual inspections of the Sloan Digital Sky Survey images of galaxy clusters in Data Release 6 （SDSS DR6）. Two of the four systems show Einstein r...We report the discovery of 4 strong gravitational lensing systems by visual inspections of the Sloan Digital Sky Survey images of galaxy clusters in Data Release 6 （SDSS DR6）. Two of the four systems show Einstein rings while the others show tangen- tial giant arcs. These arcs or rings have large angular separations （〉 8″） from the bright central galaxies and show bluer color compared with the red cluster galaxies. In addition, we found 5 probable and 4 possible lenses by galaxy clusters.展开更多
Multivariate statistical techniques,such as cluster analysis(CA),discriminant analysis(DA),principal component analysis(PCA) and factor analysis(FA),were applied to evaluate and interpret the surface water quality dat...Multivariate statistical techniques,such as cluster analysis(CA),discriminant analysis(DA),principal component analysis(PCA) and factor analysis(FA),were applied to evaluate and interpret the surface water quality data sets of the Second Songhua River(SSHR) basin in China,obtained during two years(2012-2013) of monitoring of 10 physicochemical parameters at 15 different sites.The results showed that most of physicochemical parameters varied significantly among the sampling sites.Three significant groups,highly polluted(HP),moderately polluted(MP) and less polluted(LP),of sampling sites were obtained through Hierarchical agglomerative CA on the basis of similarity of water quality characteristics.DA identified p H,F,DO,NH3-N,COD and VPhs were the most important parameters contributing to spatial variations of surface water quality.However,DA did not give a considerable data reduction(40% reduction).PCA/FA resulted in three,three and four latent factors explaining 70%,62% and 71% of the total variance in water quality data sets of HP,MP and LP regions,respectively.FA revealed that the SSHR water chemistry was strongly affected by anthropogenic activities(point sources:industrial effluents and wastewater treatment plants;non-point sources:domestic sewage,livestock operations and agricultural activities) and natural processes(seasonal effect,and natural inputs).PCA/FA in the whole basin showed the best results for data reduction because it used only two parameters(about 80% reduction) as the most important parameters to explain 72% of the data variation.Thus,this work illustrated the utility of multivariate statistical techniques for analysis and interpretation of datasets and,in water quality assessment,identification of pollution sources/factors and understanding spatial variations in water quality for effective stream water quality management.展开更多
A fundamental goal in cellular signaling is to understand allosteric communication, the process by which sig-nals originating at one site in a protein propagate reliably to affect distant functional sites. The general...A fundamental goal in cellular signaling is to understand allosteric communication, the process by which sig-nals originating at one site in a protein propagate reliably to affect distant functional sites. The general principles of protein structure that underlie this process remain unknown. Statistical coupling analysis （SCA） is a statistical technique that uses evolutionary data of a protein family to measure correlation between distant functional sites and suggests allosteric communication. In proteins, very distant and small interactions between collections of amino acids provide the communication which can be important for signaling process. In this paper, we present the SCA of protein alignment of the esterase family （pfam ID： PF00756） containing the sequence of antigen 85C secreted by Mycobacterium tuberculosis to identify a subset of interacting residues. Clustering analysis of the pairwise correlation highlighted seven important residue positions in the esterase family alignments. These resi-dues were then mapped on the crystal structure of antigen 85C （PDB ID： 1DQZ）. The mapping revealed corre-lation between 3 distant residues （Asp38, Leu123 and Met125） and suggests allosteric communication between them. This information can be used for a new drug against this fatal disease.展开更多
基金Supported by the National Natural Science Foundation of China(Grant Nos. 10821061, 10833003 and 11103032)Young Researcher Grant of National Astronomical Observatories, Chinese Academy of Sciences and the National Key Basic Research Science Foundation of China (2007CB815403)Funding for SDSS-III has been provided by the Alfred P.Sloan Foundation,the Participating Institutions,the National Science Foundation and the U.S.Department of Energy
文摘We identify new strong lensing clusters of galaxies from the Sloan Digital Sky Survey Ⅲ （SDSS DR8） by visually inspecting color images of a large sample of clusters of galaxies. We find 68 new clusters showing giant arcs in addition to 30 known lensing systems. Among 68 cases, 13 clusters are ＂almost certain＂ lensing systems with tangential giant arcs, 22 clusters are ＂probable＂ and 31 clusters are ＂pos- sible＂ lensing systems. We also find two exotic systems with blue rings. The giant arcs have angular separations of 2.0jj - 25.7j~ from the bright central galaxies. We note that the rich clusters are more likely to be lensing systems and the separations between the arcs and the central galaxies increase with cluster richness.
文摘A spatial orientation of angular momentum vectors of galaxies in six dynamically unstable Abell clusters（S1171, S0001, A1035, A1373, A1474 and A4053） is studied. For this, twodimensional observed parameters（e.g., positions, diameters and position angles） are converted into three-dimensional（3D） rotation axes of the galaxy using the ＇position angle-inclination＇ method. The expected isotropic distribution curves for angular momentum vectors are obtained by performing random simulations. The observed and expected distributions are compared using several statistical tests.No preferred alignments of angular momentum vectors of galaxies are noticed in all six dynamically unstable clusters, supporting the hierarchy model of galaxy formation. These clusters have a larger value of velocity dispersion. However, local effects are noticed in the clusters that have substructures in the1D-3D number density maps.
文摘Clusters of galaxies are the most massive objects in the Universe and precise knowledge of their mass structure is important to understand the history of structure formation and constrain still unknown types of dark contents of the Universe. X-ray spectroscopy of galaxy clusters provides rich information about the physical state of hot intracluster gas and the underlying potential structure. In this paper, starting from the basic description of clusters under equilibrium conditions, we review properties of clusters revealed primarily through X-ray observations considering their thermal and dynamical evolutions. The future prospects of cluster studies using upcoming X-ray missions are also mentioned.
文摘This paper develops an original theory of dark matter in the current ΛCDM framework, whose main hypothesis is that DM is generated by the own gravitational field, according to an unknown quantum gravitational phenomenon. This work is the best version of the theory, which I have been developing and publishing since 2014. The hypothesis of DM by quantum gravitation, DMbQG hereafter, has two main consequences: the first one is that the law of DM generation has to be the same, in the halo region, for all the galaxies and the second one is that the haloes are unbounded, so the total DM goes up without limit as the gravitational field is unbounded as well. The first one consequence is backed by the fact that M31 and MW has a fitted function with the same power exponent for the rotation curve at the halo region and both giant galaxies are the only ones whose rotation curves at the halo region may be studied with accuracy. This paper is firstly developed all the theory with M31 rotation curve data up to Chapter 9. The most important formula of the theory is the called Direct mass, which calculates the total mass at a specific radius into the halo region. Chapter 10 is dedicated to apply the theory to Milky Way, it is calculated its total mass at different radius into the halo and such results have been validated successfully using the data of masses at different radius published by two researcher teams. In Chapter 11, it is calculated the direct mass for the Local Group, and it is shown how the DMbQG theory is able to calculate the total mass at 770 kpc, that the dynamical methods estimate to be 5×1012MΘ. In Chapter 12, it is shown a method to estimate the Direct mass formula for a cluster of galaxies, using only its virial mass and virial radius. By this method, it is estimated the parameter a2 of the Local Group, which match with the one calculated in previous chapter by a different method. Also are calculated the parameters a2 associated to Virgo and Coma clusters. In Chapter 13, it is demonstrated how the DE is able to counterbalance the DM at cluster scale, as the Direct mass grows up with the square root of radius whereas the DE grows up with the cubic power. The chapter is an introduction to the DMbQG theory for cluster of galaxies, which has been developed fully by the author in other works. This theory aims to be a powerful method to study DM in the halo region of galaxies and cluster of galaxies and conversely the measures in galaxies and clusters offer the possibility to validate the theory.
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supports from the CAS Pioneer Hundred Talents Program(Category B)the National Natural Science Foundation of China(NSFC,grant No.12273037)the USTC Research Funds of the Double First-Class Initiative。
文摘Leveraging the semi-analytic method,we compute halo spins for a substantial sample of H I-bearing galaxies observed in the Arecibo Legacy Fast ALFA Survey.Our statistical analysis reveals a correlation between halo spin and environment,although the trend is subtle.On average,galaxies exhibit a decreasing halo spin tendency in denser environments.This observation contrasts with previous results from N-body simulations in the Lambda Cold Dark Matter framework.The discrepancy may be attributed to environmental gas stripping,leading to an underestimation of halo spins in galaxies in denser environments,or to baryonic processes that significantly alter the original dark matter halo spins,deviating from previous N-body simulation findings.
基金supported by the National Natural Science Foundation of China under program Nos.12090040,12090043,12473031,and 12003025as well as the Basic Research Program of Yunnan Province(No.202401AT070142)+2 种基金the International Center of Supernovae,Yunnan Key Laboratory(No.202302AN360001)the Natural Science Foundation of Yunnan Province(No.202201BC070003)the support of the Postdoctoral Fellowship Program of CPSF under grant Nos.GZC20240124 and 2024M760242.
文摘The 11th data release of the LAMOST survey provides fundamental stellar parameters but lacks detailed abundance measurements forα-elements,which are crucial for understanding stellar populations and Galactic chemical evolution.In this study,we derive the abundances of oxygen(O),magnesium(Mg),silicon(Si),calcium(Ca),and titanium(Ti)for over 6.8 million stars using LAMOST DR11 low-resolution spectra.To ensure reliable measurements,we select 760 open clusters spanning a broad range of ages and apply Monte Carlo sampling for accurate abundance estimates.Additionally,we utilize over 30,000 stars from the GALAH DR4 catalog to train an XGBoost model for extractingα-element abundances from LAMOST DR11 spectra.Bayesian linear regression is employed to analyze the compositional distribution across the Galactic disk and infer chemical gradients as a function of Galactocentric distance.Our results indicate a general increase in chemical abundances with Galactocentric distance,with oxygen showing the steepest gradient.Our results confirm the overall increase ofα-element abundances with Galactocentric distance,consistent with previous studies,while minor discrepancies in Mg,Ca,and Ti gradients likely arise from differences in sample selection,observational sensitivity,or Galactic enrichment processes.
基金supported in part by the National Natural Science Foundation of China through Grant 11821303by the Ministry of Science and Technology of China through Grant 2018YFA0404502+1 种基金support from the China Scholarship Councilthe nancial support of the GA?R EXPRO grant No.21-13491X.
文摘Previous X-ray and optical studies of the galaxy cluster pair A222/223 suggested the possible presence of a=lamentary structure connecting the two clusters,a result that appears to be supported by subsequent weak-lensing analyses.This=lament has been reported to host a primordial warm-hot intergalactic medium,which existed prior to being heated by the interactions of the clusters.In this study,we made an attempt to examine the reported emission feature with data from an archival Suzaku observation,taking advantage of its low detector background.Because the emission is expected to be very weak,we=rst carefully examined all potential sources of“contamination,”and then modeled the residual emission.Due to large uncertainties,unfortunately,our results can neither con=rm the presence of the reported emission feature nor rule it out.We discuss the sources of uncertainties.
文摘Web data extraction has become a key technology for extracting valuable data from websites.At present,most extraction methods based on rule learning,visual pattern or tree matching have limited performance on complex web pages.Through ana-lyzing various statistical characteristics of HTML el-ements in web documents,this paper proposes,based on statistical features,an unsupervised web data ex-traction method—traversing the HTML DOM parse tree at first,calculating and generating the statistical matrix of the elements,and then locating data records by clustering method and heuristic rules that reveal in-herent links between the visual characteristics of the data recording areas and the statistical characteristics of the HTML nodes—which is both suitable for data records extraction of single-page and multi-pages,and it has strong generality and needs no training.The ex-periments show that the accuracy and efficiency of this method are equally better than the current data extrac-tion method.
基金supported by National Nature Science Foundation of China(No.62361036)Nature Science Foundation of Gansu Province(No.22JR5RA279).
文摘To realize dynamic statistical publishing and protection of location-based data privacy,this paper proposes a differential privacy publishing algorithm based on adaptive sampling and grid clustering and adjustment.The PID control strategy is combined with the difference in data variation to realize the dynamic adjustment of the data publishing intervals.The spatial-temporal correlations of the adjacent snapshots are utilized to design the grid clustering and adjustment algorithm,which facilitates saving the execution time of the publishing process.The budget distribution and budget absorption strategies are improved to form the sliding window-based differential privacy statistical publishing algorithm,which realizes continuous statistical publishing and privacy protection and improves the accuracy of published data.Experiments and analysis on large datasets of actual locations show that the privacy protection algorithm proposed in this paper is superior to other existing algorithms in terms of the accuracy of adaptive sampling time,the availability of published data,and the execution efficiency of data publishing methods.
基金supported by the National Natural Science Foundation of China(NSFC)through grants 12090040,12090042,and 12073060the National Key R&D Program of China No.2019YFA0405501+2 种基金J.Z.acknowledges the Youth Innovation Promotion Association CASthe Science and Technology Commission of Shanghai Municipality(grant No.22dz1202400)the Program of Shanghai Academic/Technology Research Leader。
文摘As part of the LAMOST medium-resolution spectroscopic survey,the LAMOST-MRS-O is a non-time domain survey that aims to perform medium-resolution spectral observations for member stars in the open cluster areas.This survey plans to obtain the spectroscopic parameters such as radial velocity and metal abundances of member stars and provide data support for further study on the chemical and dynamical characteristics and evolution of open clusters in combination with Gaia data.We have completed the observations on ten open cluster fields and obtained 235184 medium-resolution spectra of 133792 stars.Based on the data analyzed of LAMOST DR11v1.1,for some clusters of particular concern,it is found that the sampling ratio of members stars with Gmag<15 mag can reach 70%,which indicates that the LAMOST-MRS-O has reached our initial design goal.
基金supported by the National Natural Science Foundation of China(NSFC,grant No.U1731128)the support of the Association for Astronomy X A.I.(A3),funded by the Science and Education Integration Funding of the University of Chinese Academy of Sciences。
文摘In the study of spiral galaxy morphology,spiral arm structures are valuable for intuitively reflecting active physical and chemical processes within galaxies.However,long-term scarcity of high-quality one-,three-,and four-armed galaxy samples has limited deep learning model performance.To address this,this study developed a spiral galaxy data simulation program with a three-stage workflow:first,screening highly reliable training samples;second,selecting the best-performing Imagen architecture as the generative model after comparing nine mainstream ones;finally,training Imagen to generate an open data set of 9402 one-/three-armed galaxies,expanding the original sample size by 6 times.Multi-dimensional evaluations verified reliability and usability:Fréchet Inception Distance scores for N=1 and N=3 tasks were 6.05 and 9.13;the t-distributed Stochastic Neighbor Embedding showed generated data covered and expanded real data distribution;the Structural Similarity Index Measure confirmed no sample duplication.In downstream validation,data augmentation improved seven classification models'average accuracy by 8.7%(DenseNet peaked at 97%),and SHapley Additive exPlanations analysis showed model decisions focused on spiral arm topology.In conclusion,the program and data set support spiral galaxy morphology deep learning research and are publicly available at https://github.com/TuAstroAILab/AstroGS.
基金supported by the National Natural Science Foundation of China,No.12261141689。
文摘Recent studies have increasingly identified extended main sequence turn-off(e MSTO)phenomena in Galactic open clusters,yet the number of such clusters with sufficient spectroscopic information for member stars remains limited.Unlike most studies that rely on fitting isochrones based on color–magnitude diagram(CMD)morphology to account for varying rotational velocities,our approach leverages LAMOST spectral data to compute actual rotational velocity distributions for confirmed cluster members,along with parameters such as metallicity,differential extinction,and rotational inclination,to utilize PARSEC isochrones for fitting the cluster CMDs.We systematically surveyed all known Galactic open clusters and selected 12 clusters where rotational velocity distributions could be reliably calculated for detailed fitting.Our results successfully reproduced the eMSTO phenomenon observed in these clusters.For the majority of clusters,considering only differential extinction and variations in rotational velocity adequately explains the position and morphology of the MSTO.For some intermediate-age clusters,incorporating rotational inclination additionally accounts for the broadening of the MSTO.This study underscores the importance of spectroscopic data in understanding eMSTO phenomena and provides a probable explanation for interpreting the combined effects of differential extinction,rotation,and inclination on the CMDs of Galactic open clusters.
基金supported by the National Natural Science Foundation of China (12473105 and 12473106)the central government guides local funds for science and technology development (YDZJSX2024D049)the Graduate Student Practice and Innovation Program of Shanxi Province (2024SJ313)
文摘As large-scale astronomical surveys,such as the Sloan Digital Sky Survey(SDSS)and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST),generate increasingly complex datasets,clustering algorithms have become vital for identifying patterns and classifying celestial objects.This paper systematically investigates the application of five main categories of clustering techniques-partition-based,density-based,model-based,hierarchical,and“others”-across a range of astronomical research over the past decade.This review focuses on the six key application areas of stellar classification,galaxy structure analysis,detection of galactic and interstellar features,highenergy astrophysics,exoplanet studies,and anomaly detection.This paper provides an in-depth analysis of the performance and results of each method,considering their respective suitabilities for different data types.Additionally,it presents clustering algorithm selection strategies based on the characteristics of the spectroscopic data being analyzed.We highlight challenges such as handling large datasets,the need for more efficient computational tools,and the lack of labeled data.We also underscore the potential of unsupervised and semi-supervised clustering approaches to overcome these challenges,offering insight into their practical applications,performance,and results in astronomical research.
文摘Making use of the 2MASS Data Release, we have searched for nearinfrared （JHK） counterparts to 268 blazars from Donato et al. and obtained 238 counterparts within 5＇＇ in the area covered by 2MASS. It provides us a sample with infrared data several times larger than the previous one of the same kind. Based on our sample and the sample by Donato et al., we have compared in detail the properties of HBLs, LBLs and FSRQs from five aspects and found that HBLs are significantly different from LBLs and FSRQs while LBLs are not obviously different from FSRQs. Our results strongly support the division of BL Lac objects into the high-frequency peaked （HBL） and low-frequency peaked （LBL） objects introduced by Padovani ＆ Giommi and show that HBLs and LBLs are two kinds of blazar having different physical properties.
基金supported by the National Natural Science Foundation of China (NSFC, Nos.10521001, 10773016 and 10833003)the National KeyBasic Research Science Foundation of China (2007CB815403).
文摘We report the discovery of 4 strong gravitational lensing systems by visual inspections of the Sloan Digital Sky Survey images of galaxy clusters in Data Release 6 （SDSS DR6）. Two of the four systems show Einstein rings while the others show tangen- tial giant arcs. These arcs or rings have large angular separations （〉 8″） from the bright central galaxies and show bluer color compared with the red cluster galaxies. In addition, we found 5 probable and 4 possible lenses by galaxy clusters.
基金Project (2012ZX07501002-001) supported by the Ministry of Science and Technology of China
文摘Multivariate statistical techniques,such as cluster analysis(CA),discriminant analysis(DA),principal component analysis(PCA) and factor analysis(FA),were applied to evaluate and interpret the surface water quality data sets of the Second Songhua River(SSHR) basin in China,obtained during two years(2012-2013) of monitoring of 10 physicochemical parameters at 15 different sites.The results showed that most of physicochemical parameters varied significantly among the sampling sites.Three significant groups,highly polluted(HP),moderately polluted(MP) and less polluted(LP),of sampling sites were obtained through Hierarchical agglomerative CA on the basis of similarity of water quality characteristics.DA identified p H,F,DO,NH3-N,COD and VPhs were the most important parameters contributing to spatial variations of surface water quality.However,DA did not give a considerable data reduction(40% reduction).PCA/FA resulted in three,three and four latent factors explaining 70%,62% and 71% of the total variance in water quality data sets of HP,MP and LP regions,respectively.FA revealed that the SSHR water chemistry was strongly affected by anthropogenic activities(point sources:industrial effluents and wastewater treatment plants;non-point sources:domestic sewage,livestock operations and agricultural activities) and natural processes(seasonal effect,and natural inputs).PCA/FA in the whole basin showed the best results for data reduction because it used only two parameters(about 80% reduction) as the most important parameters to explain 72% of the data variation.Thus,this work illustrated the utility of multivariate statistical techniques for analysis and interpretation of datasets and,in water quality assessment,identification of pollution sources/factors and understanding spatial variations in water quality for effective stream water quality management.
文摘A fundamental goal in cellular signaling is to understand allosteric communication, the process by which sig-nals originating at one site in a protein propagate reliably to affect distant functional sites. The general principles of protein structure that underlie this process remain unknown. Statistical coupling analysis （SCA） is a statistical technique that uses evolutionary data of a protein family to measure correlation between distant functional sites and suggests allosteric communication. In proteins, very distant and small interactions between collections of amino acids provide the communication which can be important for signaling process. In this paper, we present the SCA of protein alignment of the esterase family （pfam ID： PF00756） containing the sequence of antigen 85C secreted by Mycobacterium tuberculosis to identify a subset of interacting residues. Clustering analysis of the pairwise correlation highlighted seven important residue positions in the esterase family alignments. These resi-dues were then mapped on the crystal structure of antigen 85C （PDB ID： 1DQZ）. The mapping revealed corre-lation between 3 distant residues （Asp38, Leu123 and Met125） and suggests allosteric communication between them. This information can be used for a new drug against this fatal disease.
