旋涡星系图像中所蕴含的旋臂信息,尤其是旋臂数量,对研究星系结构演化和星系动力学具有重要价值.在当前星系观测数据爆发式增长的背景下,如何快速识别出旋臂数量成为旋涡星系研究的重要问题.基于Galaxy Zoo DECaLS(Dark Energy Camera L...旋涡星系图像中所蕴含的旋臂信息,尤其是旋臂数量,对研究星系结构演化和星系动力学具有重要价值.在当前星系观测数据爆发式增长的背景下,如何快速识别出旋臂数量成为旋涡星系研究的重要问题.基于Galaxy Zoo DECaLS(Dark Energy Camera Legacy Survey)数据集,研究ResNet(Residual Networks)模型从旋涡星系图像中识别旋臂数量的方法,通过对比分析ResNet在不同网络层数下的实验结果,得出具有32层网络结构的ResNet模型,即ResNet32效果最佳,其总体准确率为83%,识别效果优于ViT(Vision Transformer)、EfficientNet和DenseNet等网络模型.在对不同旋臂数量的识别方面,识别准确率与训练样本的多少有较强的关系,拥有2个旋臂的图像数量有6800张,其F1分数(F1-Score)值达到0.9,而有4个旋臂的图像数量只有237张,其F1-Score值也最低.实验进一步分析了融合传统星系图像特征的识别效果,发现融合传统星系图像特征在提升旋臂数量识别方面作用有限.展开更多
收集了Fermi Large Area Telescope第4期源表第3次修订版(Fermi Large Area Telescope Fourth Source Catalog Data Release 3, 4FGL-DR3)耀变体(Blazar)样本的多波段辐射流量密度,所收集的数据覆盖了射电1.4和143 GHz、近红外(J、H和K...收集了Fermi Large Area Telescope第4期源表第3次修订版(Fermi Large Area Telescope Fourth Source Catalog Data Release 3, 4FGL-DR3)耀变体(Blazar)样本的多波段辐射流量密度,所收集的数据覆盖了射电1.4和143 GHz、近红外(J、H和K)、可见光(u、g、r、i和z)、紫外(far ultraviolet和near ultraviolet)、X射线以及γ射线0.1–100 GeV间的6个能段(0.1–0.3、0.3–1、1–3、3–10、10–30和30–100 GeV).分析了耀变体及其子类样本的高能γ射线各能段之间以及γ射线各能段与射电至X射线多波段辐射之间的相关性.各波段流量之间的线性回归拟合结果显示:γ射线各能段之间,相关系数大于0.7的比例为70%,置信水平高于95%的比例为95%;γ射线与同步辐射之间,相关系数大于0.4的占比为42%,置信水平大于95%的占比为94.4%,有一定的相关性;未确定类型耀变体(Blazar of Unknown Types, BCU)的高能γ射线与同步辐射之间的相关性很弱,相关系数均小于0.4.分析表明:BCU样本的拟合斜率介于蝎虎天体(BL Lac Object, BLL)样本与平谱射电类星体(Flat-Spectrum Radio Quasar, FSRQ)样本之间,应是BCU样本由BLL与FSRQ的混合导致.同步辐射与γ射线辐射的相关性表明, BLL的高能γ射线主要由同步自康普顿散射(Synchrotron SelfCompton, SSC)机制主导产生, X射线可能是同步辐射与逆康普顿散射(Inverse Compton, IC)辐射的混合.展开更多
A team of researchers from the Beijing Normal University,the Institute of High Energy Physics(IHEP)under the Chinese Academy of Sciences(CAS),and the National Astronomical Observatories,CAS(NAOC),reported in Nature As...A team of researchers from the Beijing Normal University,the Institute of High Energy Physics(IHEP)under the Chinese Academy of Sciences(CAS),and the National Astronomical Observatories,CAS(NAOC),reported in Nature Astronomy on January 23,2025 their discovery of an X-ray flash about 12.5 billion lightyears away.The signals burst out only 1.2 billion years after the Big Bang,when our 13.8-billion-year-old universe was still in its infancy,and a science satellite swiftly recorded them.展开更多
We present the optical light curves of the tidal disruption event AT 2023clx in the declining phase,observed with Mephisto.Combining our light curve with the ASAS-SN and ATLAS data in the rising phase,and fitting the ...We present the optical light curves of the tidal disruption event AT 2023clx in the declining phase,observed with Mephisto.Combining our light curve with the ASAS-SN and ATLAS data in the rising phase,and fitting the composite multi-band light curves with MOSFiT,we estimate black hole mass for AT 2023clx is between 10^(5.67)and 10^(5.82)M_(⊙).This event may be caused by either a full disruption of a 0.1M_(⊙)star,or a partial disruption of a 0.99M_(⊙) star,depending on the data adopted for the rising phase.Based on those fit results and the non-detection of soft X-ray photons in the first 90 days,we propose that the observed optical radiation is powered by stream-stream collision.We speculate that the soft X-ray photons may gradually emerge in 100-600 days after the optical peak,when the debris is fully circularized into a compact accretion disk.展开更多
Based on the updated M giant star catalog selected from Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR9,we identify substructures within the integrals-of-motion space through the Friends-of-Friends clust...Based on the updated M giant star catalog selected from Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR9,we identify substructures within the integrals-of-motion space through the Friends-of-Friends clustering algorithm.We obtain members belonging to several known substructures:the Sagittarius stream,Galactic Anticenter Substructure(GASS),Gaia-Enceladus-Sausage(GES),Splash,and the high-αdisk.Furthermore,we also identify two groups which cannot be clearly associated with previously known substructures.Our findings confirm the existence of metal-rich constituents within the GES,representing newly formed stars that originated from the metal-enriched gas delivered during the GES merger event and subsequently evolved.Additionally,this study further expands the sample of GASS,high-αdisk,and Splash stars.Analysis of these metal-rich M giant stars as members of the GES,Splash,and high-αdisk components supports an evolution scenario for the early Milky Way,as proposed by previous studies.In this scenario,stars initially formed in a high-α primordial disk were dynamically heated by the massive accretion event(GES).This process redistributed stellar orbits,creating the Splash population,while the undisturbed portion of the primordial disk persisted as the present-day high-αdisk component.展开更多
In this manuscript,we report evidence to support the dependence of Dn4000(4000A break strength to trace stellar ages) on central active galactic nuclei(AGN) activity traced by narrow emission line properties in local ...In this manuscript,we report evidence to support the dependence of Dn4000(4000A break strength to trace stellar ages) on central active galactic nuclei(AGN) activity traced by narrow emission line properties in local Type-2AGN in SDSS DR 16.Based on the measured Dn4000 and flux ratios of [O Ⅲ] to narrow Hβ(O3HB) and [N Ⅱ] to narrow Hα(N2HA) and narrow Hα line luminosity L_(Hα),linear dependence of the Dn4000 on the O3HB,N2HA and L_(Hα)in the local Type-2 AGN can provide clues to support the dependence of Dn4000 on properties with narrow emission lines.Linear correlations between the Dn4000 and the O3HB and N2HA can be found in the local Type-2 AGN,with Spearman rank correlations of about-0.39 and 0.53.Meanwhile,stronger dependence of the Dn4000 on the L_(Hα)can be confirmed in Type-2 AGN,with a Spearman rank correlation coefficient of about-0.7.Moreover,combining the L_(Hα)and the N2HA,a more robust and stronger linear correlation can be confirmed between the Dn4000 and the new parameter LR=0.2 log(L_(Hα))-0.5 log(N2HA),with a Spearman rank correlation coefficient of about-0.76 and with smaller rms scatters.After considering necessary effects,the dependence of Dn4000 on LR is stable and robust enough for the local Type-2 AGN,indicating that the LR on the narrow emission lines can be treated as a better indicator to statistically trace stellar ages of samples of more luminous AGN with weaker host galaxy absorption features.展开更多
This paper investigates the star formation efficiency(SFE)of blue compact galaxies(BCGs)by analyzing various indicators,including(O II),(H_(α)),infrared emissions,and the 1.4 GHz radio continuum.The assessment of SFE...This paper investigates the star formation efficiency(SFE)of blue compact galaxies(BCGs)by analyzing various indicators,including(O II),(H_(α)),infrared emissions,and the 1.4 GHz radio continuum.The assessment of SFE was conducted using publicly accessible data that concentrated on star formation rates(SFRs)and depletion timescales.By employing the fundamental equation,I determined the SFE in relation to its freefall time,which highlighted variations in efficiencies associated with SFR masses derived from different spectra.The results demonstrated that the highest efficiency value was observed in the analysis of the 1.4 GHz radio continuum,emphasizing the importance of studying star-forming clouds across a range of electromagnetic wavelengths to achieve a comprehensive understanding of star formation mechanisms.The study's findings indicated a peak efficiency of star formation value of approximately 0.9%,while the relative minimum obtained from(O II)was around 0.42%,aligning with the range of SFEs documented in the existing literature.Additionally,investigating the factors that influence the variability in efficiency when examining clouds in BCGs across different wave bands is crucial for deepening our comprehension of the underlying processes of star formation.展开更多
We present systematic identifications of supergiants in M31/M33 based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)spectroscopic survey.Radial velocities of nearly 5000 photometrically selec...We present systematic identifications of supergiants in M31/M33 based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)spectroscopic survey.Radial velocities of nearly 5000 photometrically selected M31/M33 supergiant candidates have been properly derived from the qualified spectra released in LAMOST DR10.By comparing their radial velocities with those predicted from the rotation curve of M31,as well as utilizing Gaia astrometric measurements to exclude foreground contaminations,199 supergiant members in M31,including 168“Rank1”and 31“Rank2,”have been successfully identified.This sample contains 62 blue supergiants(BSGs,all“Rank1”),134 yellow supergiants(YSGs,103“Rank1”and 31“Rank2”)and three red supergiants(RSGs,all“Rank1”).For M33,we identify 84 supergiant members(56“Rank1”and 28“Rank2”),which include 28 BSGs(all“Rank1”),53 YSGs(25“Rank1”and 28“Rank2”)and three RSGs(all“Rank1”).So far,this is one of the largest supergiant samples of M31/M33 with full optical wavelength coverage(3700<λ<9100Å).This sample is valuable for understanding star formation and stellar evolution under different environments.展开更多
成员判定是疏散星团研究中最关键的一步,成员判定的好坏直接影响对星团基本参数的估计.首次利用数据挖掘技术中的DBSCAN(Density-Based Spatial Clustering of Applications with Noise)聚类算法对疏散星团NGC 6791和M67(NGC 2682)分别...成员判定是疏散星团研究中最关键的一步,成员判定的好坏直接影响对星团基本参数的估计.首次利用数据挖掘技术中的DBSCAN(Density-Based Spatial Clustering of Applications with Noise)聚类算法对疏散星团NGC 6791和M67(NGC 2682)分别进行了成员判定,结果表明DBSCAN聚类算法能很有效地剔除场星污染.得到的NGC6791成员星的颜色-星等图上主序清晰并呈现明显的双重主序结构,这表明NGC 6791可能有更复杂的恒星形成与演化历史.对M67的分析表明出现了质量分层现象,并且星团的核心和外围两部分有明显的相对运动.对NGC 6791和M67的分析均表明DBSCAN聚类算法是一种有效的成员判定方法,有传统成员判定方法不具备的一些优点.展开更多
文摘旋涡星系图像中所蕴含的旋臂信息,尤其是旋臂数量,对研究星系结构演化和星系动力学具有重要价值.在当前星系观测数据爆发式增长的背景下,如何快速识别出旋臂数量成为旋涡星系研究的重要问题.基于Galaxy Zoo DECaLS(Dark Energy Camera Legacy Survey)数据集,研究ResNet(Residual Networks)模型从旋涡星系图像中识别旋臂数量的方法,通过对比分析ResNet在不同网络层数下的实验结果,得出具有32层网络结构的ResNet模型,即ResNet32效果最佳,其总体准确率为83%,识别效果优于ViT(Vision Transformer)、EfficientNet和DenseNet等网络模型.在对不同旋臂数量的识别方面,识别准确率与训练样本的多少有较强的关系,拥有2个旋臂的图像数量有6800张,其F1分数(F1-Score)值达到0.9,而有4个旋臂的图像数量只有237张,其F1-Score值也最低.实验进一步分析了融合传统星系图像特征的识别效果,发现融合传统星系图像特征在提升旋臂数量识别方面作用有限.
文摘收集了Fermi Large Area Telescope第4期源表第3次修订版(Fermi Large Area Telescope Fourth Source Catalog Data Release 3, 4FGL-DR3)耀变体(Blazar)样本的多波段辐射流量密度,所收集的数据覆盖了射电1.4和143 GHz、近红外(J、H和K)、可见光(u、g、r、i和z)、紫外(far ultraviolet和near ultraviolet)、X射线以及γ射线0.1–100 GeV间的6个能段(0.1–0.3、0.3–1、1–3、3–10、10–30和30–100 GeV).分析了耀变体及其子类样本的高能γ射线各能段之间以及γ射线各能段与射电至X射线多波段辐射之间的相关性.各波段流量之间的线性回归拟合结果显示:γ射线各能段之间,相关系数大于0.7的比例为70%,置信水平高于95%的比例为95%;γ射线与同步辐射之间,相关系数大于0.4的占比为42%,置信水平大于95%的占比为94.4%,有一定的相关性;未确定类型耀变体(Blazar of Unknown Types, BCU)的高能γ射线与同步辐射之间的相关性很弱,相关系数均小于0.4.分析表明:BCU样本的拟合斜率介于蝎虎天体(BL Lac Object, BLL)样本与平谱射电类星体(Flat-Spectrum Radio Quasar, FSRQ)样本之间,应是BCU样本由BLL与FSRQ的混合导致.同步辐射与γ射线辐射的相关性表明, BLL的高能γ射线主要由同步自康普顿散射(Synchrotron SelfCompton, SSC)机制主导产生, X射线可能是同步辐射与逆康普顿散射(Inverse Compton, IC)辐射的混合.
文摘A team of researchers from the Beijing Normal University,the Institute of High Energy Physics(IHEP)under the Chinese Academy of Sciences(CAS),and the National Astronomical Observatories,CAS(NAOC),reported in Nature Astronomy on January 23,2025 their discovery of an X-ray flash about 12.5 billion lightyears away.The signals burst out only 1.2 billion years after the Big Bang,when our 13.8-billion-year-old universe was still in its infancy,and a science satellite swiftly recorded them.
基金the South-Western Institute for Astronomy Research of Yunnan University(SWIFAR-YNU),funded by the“Yunnan University Development Plan for World-Class University”and“Yunnan University Development Plan for World-Class Astronomy Discipline.”The authors acknowledge support from the“Science&Technology Champion Project”(202005AB160002)from two“Team Projects”-the“Innovation Team”(202105AE160021)the“Top Team”(202305AT350002)'funded by the“Yunnan Revitalization Talent Support Program.”。
文摘We present the optical light curves of the tidal disruption event AT 2023clx in the declining phase,observed with Mephisto.Combining our light curve with the ASAS-SN and ATLAS data in the rising phase,and fitting the composite multi-band light curves with MOSFiT,we estimate black hole mass for AT 2023clx is between 10^(5.67)and 10^(5.82)M_(⊙).This event may be caused by either a full disruption of a 0.1M_(⊙)star,or a partial disruption of a 0.99M_(⊙) star,depending on the data adopted for the rising phase.Based on those fit results and the non-detection of soft X-ray photons in the first 90 days,we propose that the observed optical radiation is powered by stream-stream collision.We speculate that the soft X-ray photons may gradually emerge in 100-600 days after the optical peak,when the debris is fully circularized into a compact accretion disk.
基金supported by the National Key Research and Development Program of China No.2024YFA1611902the National Natural Science Foundation of China(NSFC)under grants Nos.12273027 and 12588202+3 种基金the Innovation Team Funds of China West Normal University under grant No.KCXTD2022-6CAS Project for Young Scientists in Basic Research under grants Nos.YSBR-062 and YSBR-092the Strategic Priority Research Program of Chinese Academy of Sciences under grant No.XDB1160102the science research grant from the China Manned Space Project with No.CMS-CSST-2025-A11.
文摘Based on the updated M giant star catalog selected from Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR9,we identify substructures within the integrals-of-motion space through the Friends-of-Friends clustering algorithm.We obtain members belonging to several known substructures:the Sagittarius stream,Galactic Anticenter Substructure(GASS),Gaia-Enceladus-Sausage(GES),Splash,and the high-αdisk.Furthermore,we also identify two groups which cannot be clearly associated with previously known substructures.Our findings confirm the existence of metal-rich constituents within the GES,representing newly formed stars that originated from the metal-enriched gas delivered during the GES merger event and subsequently evolved.Additionally,this study further expands the sample of GASS,high-αdisk,and Splash stars.Analysis of these metal-rich M giant stars as members of the GES,Splash,and high-αdisk components supports an evolution scenario for the early Milky Way,as proposed by previous studies.In this scenario,stars initially formed in a high-α primordial disk were dynamically heated by the massive accretion event(GES).This process redistributed stellar orbits,creating the Splash population,while the undisturbed portion of the primordial disk persisted as the present-day high-αdisk component.
基金Guang Xi University for kind financial supportNSFC-12173020 and NSFC-12373014 and the the Guangxi Talent Programme (Highland of Innovation Talents) for kind grant support。
文摘In this manuscript,we report evidence to support the dependence of Dn4000(4000A break strength to trace stellar ages) on central active galactic nuclei(AGN) activity traced by narrow emission line properties in local Type-2AGN in SDSS DR 16.Based on the measured Dn4000 and flux ratios of [O Ⅲ] to narrow Hβ(O3HB) and [N Ⅱ] to narrow Hα(N2HA) and narrow Hα line luminosity L_(Hα),linear dependence of the Dn4000 on the O3HB,N2HA and L_(Hα)in the local Type-2 AGN can provide clues to support the dependence of Dn4000 on properties with narrow emission lines.Linear correlations between the Dn4000 and the O3HB and N2HA can be found in the local Type-2 AGN,with Spearman rank correlations of about-0.39 and 0.53.Meanwhile,stronger dependence of the Dn4000 on the L_(Hα)can be confirmed in Type-2 AGN,with a Spearman rank correlation coefficient of about-0.7.Moreover,combining the L_(Hα)and the N2HA,a more robust and stronger linear correlation can be confirmed between the Dn4000 and the new parameter LR=0.2 log(L_(Hα))-0.5 log(N2HA),with a Spearman rank correlation coefficient of about-0.76 and with smaller rms scatters.After considering necessary effects,the dependence of Dn4000 on LR is stable and robust enough for the local Type-2 AGN,indicating that the LR on the narrow emission lines can be treated as a better indicator to statistically trace stellar ages of samples of more luminous AGN with weaker host galaxy absorption features.
文摘This paper investigates the star formation efficiency(SFE)of blue compact galaxies(BCGs)by analyzing various indicators,including(O II),(H_(α)),infrared emissions,and the 1.4 GHz radio continuum.The assessment of SFE was conducted using publicly accessible data that concentrated on star formation rates(SFRs)and depletion timescales.By employing the fundamental equation,I determined the SFE in relation to its freefall time,which highlighted variations in efficiencies associated with SFR masses derived from different spectra.The results demonstrated that the highest efficiency value was observed in the analysis of the 1.4 GHz radio continuum,emphasizing the importance of studying star-forming clouds across a range of electromagnetic wavelengths to achieve a comprehensive understanding of star formation mechanisms.The study's findings indicated a peak efficiency of star formation value of approximately 0.9%,while the relative minimum obtained from(O II)was around 0.42%,aligning with the range of SFEs documented in the existing literature.Additionally,investigating the factors that influence the variability in efficiency when examining clouds in BCGs across different wave bands is crucial for deepening our comprehension of the underlying processes of star formation.
基金funded by the National Natural Science Foundation of China(NSFC,grant Nos.12090040,12090044,12133001,and 12422303)Beijing Natural Science Foundation(no.1242016)+2 种基金the science research grants from the China Manned Space Projectsupported by the Talents Program(24CE-YS-08)the Popular Science Project(24CD012)of the Beijing Academy of Science and Technology.
文摘We present systematic identifications of supergiants in M31/M33 based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)spectroscopic survey.Radial velocities of nearly 5000 photometrically selected M31/M33 supergiant candidates have been properly derived from the qualified spectra released in LAMOST DR10.By comparing their radial velocities with those predicted from the rotation curve of M31,as well as utilizing Gaia astrometric measurements to exclude foreground contaminations,199 supergiant members in M31,including 168“Rank1”and 31“Rank2,”have been successfully identified.This sample contains 62 blue supergiants(BSGs,all“Rank1”),134 yellow supergiants(YSGs,103“Rank1”and 31“Rank2”)and three red supergiants(RSGs,all“Rank1”).For M33,we identify 84 supergiant members(56“Rank1”and 28“Rank2”),which include 28 BSGs(all“Rank1”),53 YSGs(25“Rank1”and 28“Rank2”)and three RSGs(all“Rank1”).So far,this is one of the largest supergiant samples of M31/M33 with full optical wavelength coverage(3700<λ<9100Å).This sample is valuable for understanding star formation and stellar evolution under different environments.
