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HⅠ emission from the red giant Y CVn with the VLA and FAST

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Research in Astronomy and Astrophysics 2017年第7期17卷 39-46页

作者： Do T.Hoai Pham T.Nhung Lynn D.Matthews Eric Grard Thibaut Le Bertre Department of Astrophysics Vietnam National Satellite CenterVAST LERMA CNRSObservatoire de Paris/PSLSorbonne Universite's Department of Astrophysics Vietnam National Satellite Center MIT Haystack Observatory gepi CNRSObservatoire de Paris/PSL

Imaging studies with the Very Large Array（VLA） have revealed H I emission associated with the extended circumstellar shells of red giants. We analyze the spectral map obtained on Y CVn, a J-type carbon star on the Asymptotic Giant Branch. The H I line profiles can be interpreted with a model of a detached shell resulting from the interaction of a stellar outflow with the local interstellar medium.We reproduce the spectral map by introducing a distortion along a direction corresponding to the star＇s motion in space. We then use this fitting to simulate observations expected from the Five-hundred-meter Aperture Spherical radio Telescope（FAST）, and discuss its potential for improving our description of the outer regions of circumstellar shells.

关键词： stars AGB and post-AGB-- stars carbon - stars individual Y CVn - radio lines stars

The properties of a large volume-limited sample of face-on low surface brightness disk galaxies

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Research in Astronomy and Astrophysics 2012年第11期12卷 1486-1498页

作者： Guo-Hu Zhong Yan-Chun Liang Feng-Shan Liu Francois Hammer Karen Disseau Li-Cai Deng National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academyof Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China gepi Observatoire de Paris-Meudon 92195 Meudonl France College of Physical Science and Technology Shenyang Normal University Shenyang 110034China Univ Paris Diderot Sorbonne Paris Cit6 GEPI UMR8111 CNRS Observatoire de ParisF-92190 Meudon France

We select a large volume-limited sample of low surface brightness galax- ies （LSBGs, 2021） to investigate in detail their statistical properties and their dif- ferences from high surface brightness galaxies （HSBGs, 3639）. The distributions of stellar masses of LSBGs and HSBGs are nearly the same and they have the same me- dian values. Thus this volume-limited sample has good completeness and is further removed from the effect of stellar masses on their other properties when we compare LSBGs to HSBGs. We found that LSBGs tend to have lower stellar metallicities and lower effective dust attenuations, indicating that they have lower dust than HSBGs. The LSBGs have relatively higher stellar mass-to-light ratios, higher gas fractions, lower star forming rates （SFRs）, and lower specific SFRs than HSBGs. Moreover, with the decreasing surface brightness, gas fraction increases, but the SFRs and spe- cific SFRs decrease rapidly for the sample galaxies. This could mean that the star formation histories between LSBGs and HSBGs are different, and HSBGs may have stronger star forming activities than LSBGs.

关键词： galaxies fundamentalparameters--galaxies general--galaxies statis-tics -- galaxies stellar content

Relations between stellar mass and electron temperature-based metallicity for star-forming galaxies in a wide mass range

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Research in Astronomy and Astrophysics 2014年第7期14卷 875-890页

作者： Wei-Bin Shi Yan-Chun Liang Xu Shao Xiao-Wei Liu Gang Zhao Francois Hammer Yong Zhang Hector Flores Gui-Ping Ruan Li Zhou Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment School of Space Science and PhysicsShandong University Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of Sciences University of Chinese Academy of Sciences Kavli Institute for Astronomy and Astrophysics Peking University gepi Observatoire de Paris-Meudon Department of Physics University of Hong Kong

We select 947 star-forming galaxies from SDSS-DR7 with [O III]λ4363emission lines detected at a signal-to-noise ratio larger than 5σ. Their electron temperatures and direct oxygen abundances are then determined. We compare the results from different methods. t2, the electron temperature in the low ionization region, estimated from t3, that in the high ionization region, is compared using three analysis relations between t2- t3. These show obvious differences, which result in some different ionic oxygen abundances. The results of t3, t2, O＋＋/H＋and O＋/H＋derived by using methods from IRAF and literature are also compared. The ionic abundances O＋＋/H＋are higher than O＋/H＋for most cases. The different oxygen abundances derived from Teand the strong-line ratios show a clear discrepancy, which is more obvious following increasing stellar mass and strong-line ratio R23. The sample of galaxies from SDSS with detected [O III]λ4363 have lower metallicites and higher star formation rates, so they may not be typical representatives of the whole population of galaxies. Adopting data objects from Andrews ＆ Martini, Liang et al. and Lee et al. data, we derive new relations of stellar mass and metallicity for star-forming galaxies in a much wider stellar mass range： from 106 M to 1011 M.

关键词： galaxies： abundances -- galaxies： evolution -- galaxies： ISM -- galax-ies： spiral -- galaxies： starburst -- galaxies： stellar content

基于LAMOST-Ⅱ研究银河系盘的结构动力学以及暗物质（英文）

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基于LAMOST-Ⅱ研究银河系盘的结构动力学以及暗物质（英文）

中国天文学会2021年学术年会

作者：王海峰 gepi Observatoire de Paris

In the Gaia era,with the help of Large sky surveys such as current RAVE,LAMOST,APOGEE,GALAH,TESS,DESI catalog and future plans such as WEAVE,4MOST,PFS,MSE,CSST,etc.There is no doubt that we are entering into the golden era to investigate the formation history and structure of our home galaxy in multiple stellar populations of six-phase space by chemical tagging,time tagging,kinematics and dynamics.Our home galaxy is a typical dynamic systems that are perturbed by bar,spiral arms,warp,giant molecular clouds,dark matter subhalos,Gaia-Sausage-Enceladus,Sagittarius,LMC＆SMC,tidally disrupt satellite galaxies and so on.These processes will leave behind some imprints on stars,demonstrating abundant population structures dominated by dynamics and Galactoseismology signals.We plan to Mapping the Milky Way Disk Population Structures and Galactoseismology with large sky surveys.We will try our best to figure out:what about the population morphology of the outskirts ? Where is the truncation and how about disk stability? What are the mechanisms for so many asymmetric substructures and Galactoseismology? How do the dark matter halo,bar,spiral arms,satellites interact with the stellar,gas and dust disk? etc.Thus then,We could establish a possible theoretical framework in the future to unify or partly unify the global picture of the disk structures and origins with a possible comprehensive distribution function.There is still a long way for us to go with this project,in this talk,I will share some recent new progress about the Galactic disk with LAMOST and Gaia data,and some preliminary simulation results.

关键词：银河系暗物质

来源： cnki会议评论

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星系金属丰度的研究进展(Ⅰ):定标方法

天文学进展 2006年第4期24卷 335-361页

作者：梁艳春 HAMMER Francois 邓李才赵刚中国科学院国家天文台 gepi Observatoire de Paris-Meudon92195 MeudonFrance

金属丰度是表征星系特征的重要参量,对于理解星系的形成与演化具有重要意义。随着观测设备的不断完善与发展,已经获得越来越多的星系(包括近邻星系、中等红移及高红移星系)金属丰度的观测资料。在光致电离模型方面也取得了很大进展．这... 详细信息

金属丰度是表征星系特征的重要参量,对于理解星系的形成与演化具有重要意义。随着观测设备的不断完善与发展,已经获得越来越多的星系(包括近邻星系、中等红移及高红移星系)金属丰度的观测资料。在光致电离模型方面也取得了很大进展．这些对于理解星系中金属及恒星成分的累积历史有非常重要的作用。有多种方法可以用来估计星系的金属丰度(主要是星际介质中气相的O丰度),介绍和评述了估计星系的O丰度的多种方法,包括电子温度的方法、R23方法以及其他一些“强线”比值的方法,并给出了相应的解析公式,同时介绍了电离星云的物理本质及由光致电离模型估计星系金属丰度的方法,还给出了估计星系的C和N元素丰度的方法。

关键词：天体物理学金属丰度综述星系化学演化

星系金属丰度的研究进展(Ⅱ):光度-金属丰度关系

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天文学进展 2007年第1期25卷 22-35页

作者：梁艳春 HAMMER Francois 邓李才赵刚中国科学院国家天文台 gepi.Observatoire de Paris-Meudon 92195 MeudonFrance

金属丰度与星系光度是星系的重要特征参量,研究它们之间的关系有助于理解星系中恒星质量与金属成分的累积过程。评述了星系的光度-金属丰度关系的最新研究进展,包括对近邻星系、中等红移星系(0．42)的研究结果．由于观测样本跨越较宽的... 详细信息

金属丰度与星系光度是星系的重要特征参量,研究它们之间的关系有助于理解星系中恒星质量与金属成分的累积过程。评述了星系的光度-金属丰度关系的最新研究进展,包括对近邻星系、中等红移星系(0．42)的研究结果．由于观测样本跨越较宽的宇宙学时标,可以由此来探讨这一关系的演化过程,从而帮助理解星系演化的整体图景。

关键词：天体物理学星系综述金属丰度光度-金属丰度关系

Multiwavelength study of nearly face-on low surface brightness disk galaxies

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Research in Astronomy and Astrophysics 2010年第12期10卷 1223-1241页

作者： Dong Gao Yan-Chun Liang Shun-Fang Liu Guo-Hu Zhong Xiao-Yan Chen Yan-Bin Yang Francois Hammer Guo-Chao Yang Li-Cai Deng Jing-Yao Hu National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China ycliang @ nao. cas. cn dgao @ nao. cas. cn Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China gepi Observatoire de Paris-Meudon 92195 Meudon France Department of Physics Hebei Normal University Shijiazhuang 050016 China

We study the ages of a large sample （1802） of nearly face-on disk low surface brightness galaxies （LSBGs） using the evolutionary population synthesis （EPS） model PEGASE with an exponentially decreasing star formation rate to fit their mul- tiwavelength spectral energy distributions （SEDs） from far-ultraviolet （FUV） to nearinfrared （NIR）. The derived ages of LSBGs are 1-5 Gyr for most of the sample no matter if constant or varying dust extinction is adopted, which are similar to most of the previous studies on smaller samples. This means that these LSBGs formed the majority of their stars quite recently. However, a small part of the sample （~2%-3%） has larger ages of 5-8 Gyr, meaning their major star forming process may have occurred earlier. At the same time, a large sample （5886） of high surface brightness galaxies （HSBGs） are selected and studied using the same method for comparisons. The de- rived ages are 1-5 Gyr for most of the sample （97%） as well. These results probably mean that these LSBGs have not much different star formation histories from their HSBGs counterparts. However, we should notice that the HSBGs are generally about 0.2 Gyr younger, which could mean that the HSBGs may have undergone more recent star forming activities than the LSBGs.

关键词： galaxies： evolution -- galaxies： formation -- galaxies： photometry --galaxies： spiral -- galaxies： statistics -- ultraviolet： galaxies

On the central symmetry of the circumstellar envelope of RS Cnc

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Research in Astronomy and Astrophysics 2015年第5期15卷 713-724页

作者： Pham Tuyet Nhung Do Thi Hoai Jan Martin Winters Pierre Darriulat Eric Grard Thibaut Le Bertre VATLY INST 179 Hoang Quoc Viet Cau Giay Hanoi Vietnam LERMA UMR 8112 CNRS & Observatoire de Paris 61 av. de l’Observatoire F-75014 ParisFrance IRAM 300 rue de la Piscine Domaine Universitaire F-38406 St. Martin d’Heres France gepi UMR 8111 CNRS & Observatoire de Paris 5 Place J. Janssen F-92195 Meudon CedexFrance

We present a phenomenological study of CO（1-0） and CO（2-1） emission from the circumstellar envelope （CSE） of the Asymptotic Giant Branch （AGB） star RS Cnc. It reveals departures from central symmetry that turn out to be efficient tools for the exploration of some of the properties of the CSE. We use a wind model including a bipolar flow with a typical wind velocity of ～8 km s^-1 that decreases to ～2 km s^-1 near the equator. This wind model is used to describe Doppler velocity spectral maps obtained by merging data collected at the IRAM Plateau de Bure Interferometer and Pico Veleta single dish radio telescope. Parameters describing the wind morphology and kinematics are obtained, together with the radial dependence of the gas temperature in the domain of the CSE probed by the CO observations. Significant north-south central asymmetries are revealed by the analysis, which we quantify using a simple phenomenological description. The origin of such asymmetries is unclear.

关键词： stars AGB and post-AGB -- stars individual （RS Cnc） -- stars mass loss -- radio lines general

Chemical abundance analysis of 19 barium stars

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Research in Astronomy and Astrophysics 2016年第1期16卷 159-174页

作者： Guo-Chao Yang Yan-Chun Liang Monique Spite Yu-Qin Chen Gang Zhao Bo Zhang Guo-Qing Liu Yu-Juan Liu Nian Liu Li-Cai Deng Francois Spite Vanessa Hill Cai-Xia Zhang College of Physics and Information Engineering Hebei Normal University Shijiazhuang 050024 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China University of Chinese Academy of Sciences Beijing 100049 China gepi Observatoire de Paris-Meudon 92195 Meudon France Physics Department and Tsinghua Center for Astrophysics Tsinghua University Beijing 100084 China Astronomy Department Beijing Normal University Beijing 100875 China Department of Physics Shijiazhuang University Shijiazhuang 050035 China

We aim at deriving accurate atmospheric parameters and chemical abundances of 19 barium（Ba） stars, including both strong and mild Ba stars, based on the high signal-to-noise ratio and high resolution Echelle spectra obtained from the 2.16 m telescope at Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences. The chemical abundances of the sample stars were obtained from an LTE, plane-parallel and line-blanketed atmospheric model by inputting the atmospheric parameters（effective temperatures Teff, surface gravities log g, metallicity [Fe/H] and microturbulence velocity ξt） and equivalent widths of stellar absorption lines. These samples of Ba stars are giants as indicated by atmospheric parameters, metallicities and kinematic analysis about UVW velocity. Chemical abundances of 17 elements were obtained for these Ba stars. Their Na, Al, α- and iron-peak elements（O, Na, Mg, Al, Si, Ca,Sc, Ti, V, Cr, Mn, Ni） are similar to the solar abundances. Our samples of Ba stars show obvious overabundances of neutron-capture（n-capture） process elements relative to the Sun. Their median abundances of[Ba/Fe], [La/Fe] and [Eu/Fe] are 0.54, 0.65 and 0.40, respectively. The Y I and Zr I abundances are lower than Ba, La and Eu, but higher than the α- and iron-peak elements for the strong Ba stars and similar to the iron-peak elements for the mild stars. There exists a positive correlation between Ba intensity and [Ba/Fe].For the n-capture elements（Y, Zr, Ba, La）, there is an anti-correlation between their [X/Fe] and [Fe/H]. We identify nine of our sample stars as strong Ba stars with [Ba/Fe]〉0.6 where seven of them have Ba intensity Ba=2-5, one has Ba=1.5 and another one has Ba=1.0. The remaining ten stars are classified as mild Ba stars with 0.17〈[Ba/Fe]〈0.54.

关键词： methods： observational - stars： abundances - stars： atmospheres - stars： chemically peculiar- stars： kinematics and dynamics - stars： late-type