The spiral structure of the Milky Way represents one of the fundamental research topics in astronomy,posing a long-standing challenge.This paper provides a systematic review of the historical and recent advances in our understanding of the Galactic spiral structure.Over the past two centuries,our comprehension has undergone transformative advances-progressing from initial speculative models to direct observational evidence,and from map-ping local arm segments in the solar neighborhood to reconstructing the global spiral architecture of the Milky Way.The spiral arms of the Milky Way exhibit complex morphological characteristics;while the four-arm and two-arm models continue to be debated on global scales,the broad arrangement of nearby arms has been largely established,though detailed properties often show discrepancies among different studies.New techniques such as kinematic parameter analysis and measurements of stellar chemical abundances are offering novel avenues for investigating spiral structure.
The launch of JWST has brought astronomers a wealth of observational data on distant galaxies,which is particularly crucial in the study of galaxy interaction and galaxy mergers.JWST's infrared observation capabilities offer a unique perspective to astronomers,revealing the gas dynamics and star formation activities within galaxies.Merger events are prevalent throughout the universe,and research based on JWST observation data further confirms the significant impact of mergers on galaxy evolution.Significant progress has been made in the study of galaxies associated with JWST,including both statistical studies and individual case studies,as well as the integration of theoretical simulations with actual ob-servations.JWST also provides a unique perspective for observing emission-line galaxies,and it is widely applied in studies across various redshifts,especially in high-redshift galaxy research.JWST plays a vital role in merger galaxy research,with its infrared observation capabilities providing unprecedented advantages in exploring galaxy structure and compo-sition.Its high resolution and sensitivity make it an ideal tool for studying galaxy mergers,offering astronomers new opportunities and posing challenges in understanding galaxy evo-lution at a deeper level.
After analyzing the fitting schemes of different planes,the relationship between the de-sign of the planes and the accuracy of the surface is explored,and it can be verified that the accuracy of the reflective surface is proportional to the square of the circumferential and axial lengths of the planes.At the same time,the simulation software is used to simulate and verify different schemes,and the influence of the change of the size of the small panel on the antenna gain is explored,and it is proved that the spacing of the small panel ring is only horizontal has an effect on the energy distribution,while the width of the split in the same ring determines the energy distribution in the vertical direction.Finally,the particle swarm optimization algorithm is used to optimize and adjust the segmentation scheme of the small plate,which reduces the surface shape error,and the simula-tion experiment of the 3 m small plate scheme is carried out to verify the reliability of the method,which compensates for the 3.6%of the energy lost by the center beam caused by the change of the shape surface,and effectively reduces the newly generated side lobe power by 1.15 dB,0.77 dB,0.52 dB,1.02 dB and 2.1 dB,respectively.
Small solar system bodies with perihelion distances less than 0.307 AU/66 R⊙ are known as near-Sun small bodies, and the extreme solar heating and high-temperature magnetized plasma environments they experience can reveal information about the small bodies themselves and contribute to the understanding of the near-solar space environment. Solar satellites have obtained a large amount of measured data of near-Sun small bodies, which provide opportunities for the study of the physical characterization and evolutionary history of different groups of near-Sun comets and asteroids, as well as the comparative study of the characteristics of extreme near-Sun comets (e.g., the Kreutz group) with those of other comets. Meanwhile, the observation of the coma and tail structure of near-Sun comets provides important references for the study of coronal properties such as the magnetic field structure of the solar system space, the velocity distribution of the solar wind, the coronal electron density, and the proton temperature. This article reviews the research progress made in the observation and in-situ exploration of near-Sun small bodies by solar satellites such as SOHO, STEREO, PSP, and SolO over the past 30 years, and introduces the corresponding research methods and technical methods. Finally, the article looks forward to the prospects and development directions of current and future domestic and international space and ground-based telescope observations of near-Sun small bodies.
Future space-based gravitational wave detectors such as LISA and Taiji are expected to detect gravitational wave events from the mergers of supermassive binary black holes.In this pa-per,we find that in addition to emitting the traditional inspiral-merger-ringdown gravitational wave signals,strongly precessing supermassive binary black holes can also emit gravitational wave burst signals generated by their own spin precession,which can be observed by space-based detectors.By simulating gravitational wave signals from several precessing binary black hole systems,we assess the capability of parameter estimation from gravitational wave burst signals radiated by the black holes'intrinsic quadrupole moments,providing a feasibility analysis for testing the no-hair theorem.Utilizing the Fisher matrix method,we calculate the confidence intervals of the parameter estimations.Our results indicate that if such gravitational wave burst signals can be detected,this would directly confirm the existence of quadrupole moments in black holes.By cross-verifying with gravitational wave signals from the inspiral-merger-ringdown phases,the no-hair theorem can be further tested.
Large-scale structures of galaxies extending scales up to hundreds of parsecs are also known as the cosmic web.These structures are classified into voids,filaments,walls,and nodes based on both geometric features and galaxy number density distributions.Compared with the void environment,galaxies residing in the neighborhood of filaments usually have higher stellar mass and higher fraction of early-type red galaxies.Observations and simulations demonstrate that star formation activity declines as galaxies approach filaments.However,several factors might induce uncertainties:different algorithms result in differences among the reconstructed cosmic web;there are different methods to measure and quantify the geometric properties of filaments;in the vicinity of filaments,the stellar mass,the local galaxy density as well as halo mass are higher,which also induce variations in the star formation activity.Algorithms for finding the cosmic web structures are compared,and when factors such as stellar mass,local galaxy density and halo mass are under controlled,the effects of filaments on star formation are reviewed,with the goal of understanding how star formation is affected by the filament environment.
Low-frequency radio point sources play a crucial role in astronomical research.Besides helping to understand the evolutionary history of galaxies,they also serve as a major foreground contamination in the detection of the 21 cm signal from the Epoch of Reionization(EoR signal).Observations at low frequencies are essential for studying and comprehending the properties of radio point sources.This paper describes the radiation mechanisms of radio point sources and presents catalogues from current low-frequency radio point source observations.These catalogues signif-icantly aid in the study of radio point source classification,redshift distribution,flux distribution,luminosity function,and spectral indices.Additionally,detailed descriptions are provided for the simulation methods of major existing radio point source simulation software and the resulting radio point source catalogues.These simulation tools and data are of paramount importance for a profound understanding of the statistical properties and cosmological significance of radio point sources.
The Sgr A lobes consist of a pair of 15-parsec-sized bipolar bubbles with co-aligned ma-jor axes perpendicular to the Galactic plane observed in X-ray and radio wavelengths of the Galactic center(GC).Their sharp edges found in X-ray observations indicate that they may be enclosed by forward shocks driven by an explosive event at the GC.A recent active galactic nucleus(AGN)ac-tivity is a potential mechanism to explain the formation of the lobes,and thus their formation history is very helpful in understanding the high-energy processes occurring at the GC.Our hydrodynamic simulations show that a pair of AGN jets lasting for 500 years can effectively reproduce the mor-phology,density,temperature,and X-ray surface brightness distribution of the observed Sgr A lobes well.However,the real formation history of the lobes is still uncertain,and other competing models,including the tidal disruption event outflow model,are still possible to be the origin of the lobes.Further multi-wavelength observations will enable us to impose tighter constraints on the origin of the Sgr A lobes.
外流是一种非常重要的类星体反馈形式，对了解类星体与宿主星系的共同演化过程具有 重要意义。收集了研究外流吸收线速度漂移的相关文献，对其中的案例数据进行整理，并对比分 析吸收线速度漂移的识别方法、识别难点和产生机制，探讨了该领域未来研究方向。尽管目前吸 收线速度漂移的实测案例有限且物理机制尚不明晰，但随着类星体巡天数据的增长及数据处理 技术的进步，相关研究有望实现突破。对吸收线速度漂移的研究不仅能够深化对类星体外流现象 的理解，还将为星系演化研究提供新视角。
During the operation of ground-based laser interferometric gravitational wave detectors,the internal optical systems are subject to various noise disturbances,resulting in uncontrollable displacements.To enhance the sensitivity of the detectors and enable the detection of faint gravitational wave signals,it is imperative to employ a length sensing and control system.This system ensures that multiple optical cavities within the detector remain in resonance,thereby facilitating the design of gravitational wave signal readout schemes.Beginning with the configuration of laser interferometric gravitational wave detectors,this paper outlines the fundamental principles of length feedback control and parameter design criteria.Drawing on specific parameters of the Advanced LIGO,Advanced Virgo,and KAGRA control systems currently in operation,a detailed exposition is provided on the working principles and applications of length sensing and control systems in gravitational wave detectors.
The servo system of the radio telescope's driving motor exhibits speed mismatch during operation,which restricts the high-precision pointing and tracking control of the tele-scope.With the aperture of the telescope increases and precision improves,this issue will significantly impact the high-precision control of pointing and tracking for large-aperture radio telescopes.To reduce speed deviations in the servo system and enhance the pointing accuracy of the radio telescope,a robust motor synchronization controller based on mod-el predictive control(MPC)is designed.To address external disturbances and unmodeled errors,disturbance observer(DOB)is designed based on the system's state-space model to estimate total disturbances.Additionally,Luenberger observer(LOB)is designed to esti-mate the system's states.Combining these observers with MPC,quadratic cost function is designed to regulate the load angle and motor speed.This ensures motor speed synchroniza-tion while maintaining tracking control effectiveness.Simulation and experimental results demonstrate that compared to conventional proportion-integration(PI)controllers combined with cross-coupled structures(CS),MPC+DOB+LOB enhances the servo system's dynamic performance and synchronization capabilities.
Mantle convection plays a key role in the evolution of terrestrial planets.The latest research progress on mantle convection in terrestrial planets and large satellites is reviewed in this paper with the method of comparative planetology,which concentrates on three main issues,which are (1)Does mantle convection exist within terrestrial planets? (2)If mantle convection exists,what are its convection regime and characteristics? (3)What conditions are required for mantle convection to occur in terrestrial planets? The principal factors that significantly influence mantle convection are also discussed,in-cluding the mantle geometry and scale,material property,driving mechanism,fluid viscosity,thermal and kinematic boundary conditions,differentiation and phase transformation.It further addresses mantle convection and convection in ice shell of some large satellites.Elu-cidating the causes,mechanisms,and effects of mantle convection across different celestial bodies holds significant implications for understanding the planetary internal dynamics and planetary evolutions.
近两年，中国在红外探测器研制方面取得了突破性的进展。针对天文观测需求，对该款 红外探测器开展了天文探测所有关注指标的全面测试，获得了红外探测器的读出噪声、暗电流、 满阱、动态范围、非线性、非均匀性、量子效率等重要指标，判断了该探测器在红外天文方面的 观测能力。还利用中国科学院上海天文台佘山 1.56 m 望远镜进行实际外场观测，验证了该探测 器地面应用已经接近国外探测器同等水平，这标志着中国红外天文已进入了一个能够利用自主 研发的红外探测器在近红外特定波段开展天文观测的阶段。
自动化天文数据处理流水线的高效运行依赖于精准的定标参考数据推荐机制。因此，完 善的定标参考数据系统应运而生。系统地回顾了国际主流望远镜采用的定标参考数据推荐方法， 并深入分析了各方法的优缺点。重点介绍了一种基于文本规则的新型推荐策略和配套的定标参 考数据系统，以及其在自动化数据处理中的灵活性和高效性。此外，详细阐述了该系统在中国空 间站工程巡天空间望远镜（CSST）科学数据处理中的关键作用和潜在应用价值，并展望了其未 来的发展前景。该研究为天文数据处理中定标参考数据的推荐提供了新的思路和方法，具有重要 的理论和实践意义。
作为探测宇宙再电离时期的重要方法之一，低频全天总功率实验的核心目标是在频谱为50～200 MHz的全天总功率谱中寻找宇宙再电离时期极其微弱的中性氢21 cm信号。目前通常使用快速傅里叶变换（fast Fourier transform, FFT）来计算功率谱，其存在的频谱泄漏问题，使得射频干扰（radio frequency interference, RFI）无法彻底剔除，从而严重干扰了微弱的宇宙再电离信号的提取。多相滤波器组（polyphase filter bank, PFB）是一种将信号按频率均匀划分的技术，可以替代FFT计算功率谱。介绍了PFB的基本原理及基于统一计算架构（compute unified device architecture, CUDA）的实现，并且通过仿真比较了PFB和FFT的性能，还比较了不同阶数的PFB性能差异。结果表明，PFB技术具有更平坦的带通响应、更窄的过渡带、更好的带外抑制。最后，对天马望远镜的观测数据及低频总功率实验产生的数据进行处理，验证了PFB技术的优越性，为全天总功率实验的频谱分析提供了一种有效的解决方法。
The small bodies in the outer solar system mainly include Centaurs and trans-Neptunian objects,which contain methane,water ice,ammonia and so on,representing the most primitive bodies of the solar system.Studying the properties of small objects can help understand the origin and evolutionary history of the solar system and reveal their relationship with water and life on Earth.Currently,deep space exploration has entered a new era of vigorous development.The New Horizons spacecraft will continue to fly to the Kuiper Belt to visit these distant objects.China is also carrying out science missions to explore the boundary of the Solar System.This paper introduces the exploration and research advance of small bodies in the outer solar system from the aspects of detection history,albedo and size distribution,orbital distribution,color index,spectral properties,etc.,with a focus on their visible light,near-infrared and mid-infrared spectral properties.Future research trends will be discussed to provide support for China's missions to explore the outer solar system and icy moons.
The density of small solar system objects is very important for understanding their origin and evolutionary history.However,the determination of the densities of small solar system objects is still a challenging work so far.The binary asteroids provide an oppor-tunity to infer their density.The contact binary asteroid is one type of synchronous binary asteroids,whose orbital semi-major axis is close to the sum of the maximum semi-major axes of two asteroids assuming ellipsoid shapes.Till now,similar systems have been discovered in other small object groups of the solar system,for example,Near-Earth asteroids,Tro-jans,and Kuiper Belt objects.Considering a rubble pile structure of asteroids,the Roche binary asteroid theory can be applied to determine the system parameters including density of asteroids.Asteroid(2572)Annschnell is found possible to be a contact binary asteroid due to special features in its lightcurves obtained by the Yunnan-Hong Kong Wide Field Survey in 2017.A brightness model of the contact binary asteroid is developed,with which the photometric data of(2572)Annschnell are analysed then.The most possible value of density of this binary asteroid is 3.15 g/cm3,which is close to that of CV and CK meteorites.Based on the estimate of the normalised rotation rateΩ=0.34 and the dimensionless total angular momentum H=0.48,it is conjectured that this binary asteroid may be formed by the rotational fission of a spinning asteroid.
电离层效应的高精度校准不仅是宇宙再电离时代信号探测的关键，也是所有低频 (通常小 于 300 MHz) 射电干涉阵观测面临的关键问题。为了提高成像动态范围，最终实现望远镜的科学 目标，有必要对电离层的特性、在射电干涉阵成像中的影响以及校准方法进行研究。首先从射电 干涉阵成像原理上分析了电离层对基线引起的相位误差、以及由此引起的源位置偏移，在此基础 上进一步系统地阐述了现有电离层监测数据、预测模型以及当前在射电干涉阵领域的电离层仿 真方法和校准技术。对电离层效应的全面综述与深入分析，将为低频射电干涉阵成像领域的数据 仿真、校准提供基础支撑。
The galactic bar is a ubiquitous morphological structure in the nearby universe.There is an interaction between the bar and the host galaxy,which affects the physical properties of the host galaxy and drives secular evolution in the host galaxy.In recent years,many important progress on the evolutionary relationship between bars and galaxies have been made in observational studies.The research and identification methods of bars tend to be diversified,and the influence of bars on the evolution of galaxies and the physical mechanism are becoming more and more complete.Firstly,the influence of bars on the evolution of galaxies is introduced,and the emphasis is the effect of bars on the formation of stars in galaxies.Secondly,the distribution of bars in galaxies is analyzed,while the characteristics of barred spiral galaxies and the evolution of bars with red shift are described.Then,several main methods for identifying bars are summarized and discussed.Finally,the research on the relationship between bars and galaxies is summarized and prospected.
LP UMa 是一颗 g 波段亮度为 13.34 mag 的 W UMa 型相接双星，1997 年首次被观测 到，至今已有超过 25 a 的观测时间跨度，近 400 条极小时刻记录。多年来有数位研究者使用不 同的数据和方法对其进行了研究，得出了不同的结论。自 2022 年 12 月―2023 年 12 月，对相 接双星 LP UMa 进行了 8 次观测，得到了 11 个极小时刻；同时从 TESS 数据库和 AAVSO 数 据库中分别收集 130 和 35 个极小时刻，以及来自文献的 214 个极小时刻。基于这 390 个极小时 刻重新研究了 LP UMa 的轨道周期变化，修正了之前作者关于该系统的轨道周期正在迅速增加 和两子星之间存在快速的物质转移的结论。研究表明，LP UMa 轨道周期的快速增加其实是周 期性变化的一部分，很可能是第三天体的光时轨道效应引起了该系统 O – C 曲线的周期性变化， 并算出第三天体的周期约为 41.7 a，轨道偏心率约为 0.070 1，证实了 LP UMa 很可能也是一个 存在第三天体的晚型相接双星系统。
