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Low Surface Brightness Galaxies Selected by Different Model Fitting

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Research in astronomy and Astrophysics 2024年第1期24卷 223-236页

作者： Bing-Qing Zhang Hong Wu Wei Du Pin-Song Zhao Min He Feng-Jie Lei key laboratory of optical astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China School of astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

We present a study of low surface brightness galaxies(LSBGs) selected by fitting the images for all the galaxies inα.40 SDSS DR7 sample with two kinds of single-component models and two kinds of two-component models(disk+bulge):single exponential,single sersic,exponential+deVaucular(exp+deV),and exponential+sérsic(exp+ser).Under the criteria of the B band disk central surface brightness μ_(0,disk)(B)≥22.5 mag arcsec^(-2) and the axis ratio b/a> 0.3,we selected four none-edge-on LSBG samples from each of the models which contain 1105,1038,207,and 75 galaxies,*** are 756 galaxies in common between LSBGs selected by exponential and sersic models,corresponding to 68.42% of LSBGs selected by the exponential model and 72.83% of LSBGs selected by the sersic model,the rest of the discrepancy is due to the difference in obtaining μ_(0) between the exponential and sersic *** on the fitting,in the range of 0.5≤n≤1.5,the relation of μ_(0) from two models can be written as μ_(0,sérsic)-μ_(0,exp)=-1.34(n-1).The LSBGs selected by disk+bulge models(LSBG_(2)comps) are more massive than LSBGs selected by single-component models(LSBG_1comp),and also show a larger disk *** the bulges in the majority of our LSBG_(2)comps are not prominent,more than 60% of our LSBG_(2)comps will not be selected if we adopt a single-component model *** also identified 31 giant low surface brightness galaxies(gLSBGs) from LSBG_(2)*** are located at the same region in the color-magnitude diagram as other *** we compared different criteria of gLSBGs selection,we find that for gas-rich LSBGs,M_(*)> 10^(10)M_⊙ is the best to distinguish between gLSBGs and normal LSBGs with bulge.

关键词： catalogs galaxies:spiral galaxies:bulges methods:data analysis methods:statistical

Improving the underwater navigation performance of an IMU with acoustic long baseline calibration

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Satellite Navigation 2024年第1期5卷 224-239页

作者： Paipai Wu Wenfeng Nie Yangfan Liu Tianhe Xu Shandong key laboratory of optical astronomy and Solar-Terrestrial Environment Institute of Space SciencesShandong UniversityWeihai264209ShandongChina Research Group of astronomy and Geomatics(gAGE) Universitat Politecnica de Catalunya(UPC)BarcelonaSpain

Underwater acoustic Long-Baseline System(LBL)is an important technique for submarine positioning and ***,the high cost of the seafloor equipment and complex construction of a seafloor network restrict the distribution of the LBL within a small area,making an underwater vehicle difficult for long-distance and high-precision acoustic-based or inertial-based *** therefore propose an acoustic LBL-based Inertial Measurement Unit(IMU)calibration *** the underwater vehicle can receive the acoustic signal from a seafloor beacon,the IMU is precisely calibrated to reduce the cumulative error of Strapdown Inertial Navigation System(SINS).In this way,the IMU is expected to maintain a certain degree of accuracy by relying solely on SINS when the vehicle reaches out the range of the LBL network and cannot receive the acoustic *** present the acoustic LBL-based IMU online calibration model and analyze the factors that affect the accuracy of IMU *** results fulfill the expectation that the gyroscope bias and accelerometer bias are the main error sources that affect the divergence of SINS position errors,and the track line of the underwater vehicle directly affects the accuracy of the calibration *** addition,we deduce that an optimal calibration trajectory needs to consider the effects of the three-dimensional observability and position dilution of *** the experiment,we compare the effects of seven calibration trajectories:straight and diamond-shaped with and without the change of depth,and three sets of curves with the change of depth:circular,S-shaped,and *** them,we find that the figure-eight is the optimal trajectory for acoustic LBL-based IMU online *** take the maintenance period during which the accumulated SINS Three Dimensional(3D)position errors are below 1 km to evaluate the calibration *** filed experimental results show that for the Micro-electromechanical System

关键词： Acoustic LBL Online IMU calibration SINS Relay reference network

Multi-carrier Tb/s silicon photonic coherent receiver

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Science China(Information Sciences) 2024年第1期67卷 284-291页

作者： Zhen WANG Xingfeng LI Jingchi LI Jian SHEN Yong ZHANG Yikai SU State key lab of Advanced optical Communication Systems and Networks Department of Electronic EngineeringShanghai Jiao Tong University

We propose a silicon polarization-diversity coherent receiver for wavelength-multiplexing transmission without using the large-footprint arrayed waveguide grating(AWG).We have integrated our proposed coherent receiver on the silicon-on-insulator(SOI) platform for high-capacity *** the proposed coherent receiver,high-frequency photocurrent signals from other wavelengths are suppressed by electrical low-pass ***,the signal-signal beat interference(SSBI) generated from each wavelength is eliminated by the balanced *** two features lend to the proposed coherent receiver being free of the mm-scale *** have demonstrated our proposed coherent receiver to detect a 1.12-Tb/s wavelength-division-multiplexed and polarization-division-multiplexed 16-ary quadrature amplitude modulation(PDM-16-QAM) *** compact footprint of the silicon chip promises small-form-factor receivers for future ultra-high-capacity coherent communication systems that require a high integration level and low fabrication cost.

关键词： silicon photonics optical receivers coherent communication wavelength-division-multiplexing(WDM) polarization-division-multiplexing(PDM)

CSST Dense Star Field Preparation: A Framework for Astrometry and Photometry for Dense Star Field Images Obtained by the China Space Station Telescope(CSST)

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Research in astronomy and Astrophysics 2024年第7期24卷 161-172页

作者： Yining Wang Rui Sun Tianyuan Deng Chenghui Zhao Peixuan Zhao Jiayi Yang Peng Jia Huigen Liu Jilin Zhou College of Electronic Information and optical Engineering Taiyuan University of Technology School of astronomy&Space Science Nanjing University Peng Cheng lab

The China Space Station Telescope(CSST) is a telescope with 2 m diameter, obtaining images with high quality through wide-field observations. In its first observation cycle, to capture time-domain observation data, the CSST is proposed to observe the Galactic halo across different epochs. These data have significant potential for the study of properties of stars and exoplanets. However, the density of stars in the Galactic center is high, and it is a well-known challenge to perform astrometry and photometry in such a dense star field. This paper presents a deep learning-based framework designed to process dense star field images obtained by the CSST, which includes photometry, astrometry, and classifications of targets according to their light curve periods. With simulated CSST observation data, we demonstrate that this deep learning framework achieves photometry accuracy of 2% and astrometry accuracy of 0.03 pixel for stars with moderate brightness mag = 24(i band), surpassing results obtained by traditional methods. Additionally, the deep learning based light curve classification algorithm could pick up celestial targets whose magnitude variations are 1.7 times larger than magnitude variations brought by Poisson photon noise. We anticipate that our framework could be effectively used to process dense star field images obtained by the CSST.

关键词： astrometry methods: data analysis techniques: photometric

Mid-infrared Period–Luminosity Relations of Gaia DR3 Long Period Variables

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Research in astronomy and Astrophysics 2024年第7期24卷 59-73页

作者： Xiaohan Chen Xiaodian Chen Licai Deng Shu Wang Tianlu Chen Department of Physics College of ScienceTibet University key laboratory of Cosmic Rays (Tibet University) Ministry of Education CAS key laboratory of optical astronomy National Astronomical ObservatoriesChinese Academy of Sciences School of astronomy and Space Science University of the Chinese Academy of Sciences Department of astronomy China West Normal University Institute for Frontiers in astronomy and Astrophysics Beijing Normal University

Long period variable（LPV） stars are very promising distance indicators in the infrared bands. We selected asymptotic giant branch（AGB） stars in the Large and Small Magellanic Cloud（LMC and SMC） from the Gaia Data Release 3 LPV catalog, and classified them into oxygen-rich（O-rich） and carbon-rich（C-rich） AGB *** the Wide-field Infrared Survey Explorer database, we determined the W1-and W2-band period–luminosity relations（PLRs） for each pulsation-mode sequence of AGB stars. The dispersion of the PLRs of O-rich AGB stars in sequences C' and C is relatively small, around 0.14 mag. The PLRs of LMC and SMC are consistent in each sequence. In the W2 band, the PLR of large-amplitude C-rich AGB stars is steeper than that of small-amplitude C-rich AGB stars, due to their more circumstellar dust. By two methods, we find that some PLR sequences of O-rich AGB stars in the LMC are dependent on metallicity. The coefficients of the metallicity effect are β = –0.533 ± 0.213 mag dex1and β = –0.767 ± 0.158 mag dex1for sequence C in W1 and W2 bands, respectively. The significance of the metallicity effect in W1 band for the four sequences is 2.2-3.5σ. Both of these imply that distance measurements using O-rich Mira may need to take the metallicity effect into account.

关键词： infrared: stars stars: distances stars: variables: general

On the Performances of Estimating Stellar Atmospheric Parameters from CSST Broad-band Photometry

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Research in astronomy and Astrophysics 2024年第4期24卷 161-173页

作者： Rui-Feng Shi Yang Huang Xin-Yi Li Hua-Wei Zhang School of astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China South-Western Institute for astronomy Research Yunnan UniversityKunming 650500China CAS key lab of optical astronomy Key Laboratory of Space Astronomy and TechnologyNational Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China College of Physics and Electronic Engineering Qilu Normal UniversityJinan 250200China Department of astronomy School of PhysicsPeking UniversityBeijing 100871China Kavli Institute for astronomy and Astrophysics Peking UniversityBeijing 100871China

Deriving atmospheric parameters of a large sample of stars is of vital importance to understand the formation and evolution of the Milky *** surveys,especially those with near-ultraviolet filters,can offer accurate measurements of stellar parameters,with the precision comparable to that from low/medium resolution *** this study,we explore the capability of measuring stellar atmospheric parameters from Chinese Space Station Telescope(CSST)broad-band photometry(particularly in the near-ultraviolet bands),based on synthetic colors derived from model *** find that colors from the optical and near-ultraviolet filter systems adopted by CSST show significant sensitivities to the stellar atmospheric parameters,especially the *** to our mock data tests,the precision of the photometric metallicity is quite high,with typical values of0.17 and 0.20 dex for dwarf and giant stars,*** precision of the effective temperature estimated from broad-band colors are within 50 K.

关键词： methods:data analysis stars:abundances surveys

Astronomical Test with CMOS on the 60 cm Telescope at the Xinglong Observatory,NAOC

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Research in astronomy and Astrophysics 2024年第5期24卷 85-102页

作者： Hai-Yang Mu Zhou Fan Yi-Nan Zhu Yu Zhang Hong Wu key laboratory of optical astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101People’s Republic of China School of astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049People’s Republic of China

This work shows details of an evaluation of an observational system comprising a complementary metal-oxidesemiconductor detector, 60 cm telescope and filter complement. The system’s photometric precision and differential photometric precision, and extinction coefficients were assessed through observations of Supersky flat fields, open clusters, standard stars and exoplanets. Photometry was precision achieved at the 0.02 mag level, with differential photometry of 0.004 mag precision. Extinction was found to agree with previous studies conducted at Xinglong Observatory. Ultimately, the results demonstrate this observing system is capable of precision scientific observations with a charge-coupled device across the optical wavelengths.

关键词： atmospheric effects-instrumentation detectors-techniques polarimetric-stars atmospheres-eclipses

Kinetic scale magnetic holes in the terrestrial magnetosheath:A review

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Science China Earth Sciences 2024年第9期67卷 2739-2771页

作者： Quanqi SHI Shutao YAO Maria HAMRIN Ji LIU Shandong Provincial key laboratory of optical astronomy and Solar-Terrestrial Environment Institute of Space SciencesShandong University Department of Physics Ume? University Department of Physics University of Alberta

Magnetic holes at the ion-to-electron kinetic scale(KSMHs) are one of the extremely small intermittent structures generated in turbulent magnetized plasmas. In recent years, the explorations of KSMHs have made substantial strides, driven by the ultra-high-precision observational data gathered from the Magnetospheric Multiscale(MMS) mission. This review paper summarizes the up-to-date characteristics of the KSMHs observed in Earth's turbulent magnetosheath, as well as their potential impacts on space plasma. This review starts by introducing the fundamental properties of the KSMHs, including observational features, particle behaviors, scales, geometries, and distributions in terrestrial space. Researchers have discovered that KSMHs display a quasi-circular electron vortex-like structure attributed to electron diamagnetic drift. These electrons exhibit noticeable non-gyrotropy and undergo acceleration. The occurrence rate of KSMH in the Earth's magnetosheath is significantly greater than in the solar wind and magnetotail, suggesting the turbulent magnetosheath is a primary source region. Additionally, KSMHs have also been generated in turbulence simulations and successfully reproduced by the kinetic equilibrium models. Furthermore,KSMHs have demonstrated their ability to accelerate electrons by a novel non-adiabatic electron acceleration mechanism, serve as an additional avenue for energy dissipation during magnetic reconnection, and generate diverse wave phenomena, including whistler waves, electrostatic solitary waves, and electron cyclotron waves in space plasma. These results highlight the magnetic hole's impact such as wave-particle interaction, energy cascade/dissipation, and particle acceleration/heating in space *** end this paper by summarizing these discoveries, discussing the generation mechanism, similar structures, and observations in the Earth's magnetotail and solar wind, and presenting a future extension perspective in this active field.

关键词： Magnetic hole Whistler Magnetic dip/cavity Electron vortex Magnetosheath Turbulence Coherent structure Mirror mode Kinetic scale Electron acceleration

Morphological Classification of Infrared Galaxies Based on WISE

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Research in astronomy and Astrophysics 2024年第4期24卷 222-236页

作者： Zhi-Ren Pan Bo Qiu Cui-Xiang Liu A-Li Luo Xia Jiang Xiao-Yu Guo School of Electronic and Information Engineering Hebei University of TechnologyTianjin 300401China key laboratory of optical astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China

This study introduces a novel convolutional neural network,the WISE Galaxy Classification Network(WGC),for classifying spiral and elliptical galaxies using Wide-field Infrared Survey Explorer(WISE)*** attains an accuracy of 89.03%,surpassing the combined use of K-means or SVM with the Color-Color method in more accurately identifying galaxy *** enhanced variant,WGC_mag,integrates magnitude parameters with image features,further boosting the accuracy to 89.89%.The research also delves into the criteria for galaxy classification,discovering that WGC primarily categorizes dust-rich images as elliptical galaxies,corresponding to their lower star formation rates,and classifies less dusty images as spiral *** paper explores the consistency and complementarity of WISE infrared images with SDSS optical images in galaxy morphology *** SDSS Galaxy Classification Network(SGC),trained on SDSS images,achieved an accuracy of 94.64%.The accuracy reached 99.30% when predictions from SGC and WGC were *** the complementarity of features in WISE and SDSS images,a novel variant of a classifier,namely the Multi-band Galaxy Morphology Integrated Classifier,has been *** classifier elevates the overall prediction accuracy to 95.39%.Lastly,the versatility of WGC was validated in other data *** the HyperLEDA data set,the distinction between elliptical galaxies and Sc,Scd and Sd spiral galaxies was most pronounced,achieving an accuracy of 90%,surpassing the classification results of the Galaxy Zoo 2 labeled WISE data *** research not only demonstrates the effectiveness of WISE images in galaxy morphology classification but also represents an attempt to integrate multi-band astronomical data to enhance understanding of galaxy structures and evolution.

关键词： methods:data analysis infrared:galaxies galaxies:spiral galaxies:elliptical and lenticular cD