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Chemo-dynamical modelling with Schwarzschild's method

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Research in Astronomy and astrophysics 2018年第12期18卷 1-8页

作者： Richard John Long Shude Mao National Astronomical Observatories Chinese Academy of Sciences jodrell bank centre for astrophysics School of Physics and Astronomy The University of Manchester Physics Department and Tsinghua centre for astrophysics Tsinghua University

We extend Schwarzschild’s dynamical modelling method to model absorption line strength data as well as the more usual luminosity and kinematic data.Our approach draws on earlier published work by the first author with the Syer & Tremaine made-to-measure(M2M) dynamical modelling method and uses similar ideas to create a chemo-Schwarzschild method.We apply our extended Schwarzschild method to the same four early type galaxies(NGC 1248, NGC 3838, NGC 4452,NGC 4551) as the chemo-M2M work, and are able to recover successfully the 2D absorption line strength for the three lines we model(Hβ, Fe5015, Mg b).We believe that this is the first time Schwarzschild’s method has been used in this way.The techniques developed can be applied to modelling other aspects of galaxies, for example age and metallicity data coming from stellar population modelling, and are not specific to absorption line strength data.

关键词： galaxies:abundances galaxies:formation galaxies:individual(NGC 1248,NGC 3838,NGC 4452,NGC 4551) galaxies:kinematics and dynamics galaxies:structure methods:numerical

Stellar dynamical modeling-accuracy of 3D density estimation for edge-on axisymmetric galaxies

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Research in Astronomy and astrophysics 2021年第6期21卷 403-423页

作者： Richard J.Long Sheng-Dong Lu Dan-Dan Xu Department of Astronomy Tsinghua UniversityBeijing 100084China jodrell bank centre for astrophysics Department of Physics and AstronomyThe University of ManchesterOxford RoadManchester M139PLUK

From Rybicki’s analysis using the Fourier slice theorem,mathematically it is possible to reproduce uniquely an edge-on axisymmetric galaxy’s 3D light distribution from its 2D surface brightness.Utilizing galaxies from a cosmological simulation,we examine the ability of Syer and Tremaine’s madeto-measure method and Schwarzschild’s method for stellar dynamical modeling to do so for edge-on oblate axisymmetric galaxies.Overall,we find that the methods do not accurately recover the 3D distributions,with the made-to-measure method producing more accurate estimates than Schwarzschild’s method.Our results have implications broader than just luminosity density,and affect other luminosity-weighted distributions within galaxies,for example,age and metallicity.

关键词： galaxies:kinematics and dynamics galaxies:structure methods:numerical

Made-to-measure galaxy modelling utilising absorption line strength data

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Research in Astronomy and astrophysics 2016年第12期16卷 89-100页

作者： R.J.Long National Astronomical Observatories Chinese Academy of SciencesBeijing 100012China jodrell bank centre for astrophysics School of Physics and Astronomythe University of ManchesterOxford RoadManchester M13 9PLUK

We enhance the Syer ＆ Tremaine made-to-measure （M2M） particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data, thus creating a ＇chemo-M2M＇ modelling scheme. We apply the enhanced method to four galaxies （NGC 1248, NGC 3838, NGC 4452, NGC 4551） observed using the SAURON integral-field spectrograph as part of the ATLAS3D programme. We are able to reproduce successfully the 2D line strength data achieving mean X2 per bin values of ≈ 1 with 〉 95% of particles having converged weights. Because M2M uses a 3D particle system, we are also able to examine the underlying 3D line strength distributions. The extent to which these dis- tributions are plausible representations of real galaxies requires further consideration. Overall, we consider the modelling exercise to be a promising first step in developing a ＇chemo-M2M＇ modelling system and in understanding some of the issues to be addressed. While the made-to-measure techniques developed have been applied to absorption line strength data, they are in fact general and may be of value in modelling other aspects of galaxies.

关键词： galaxies： abundances --galaxies： formation- galaxies： individual （NGC 1248 NGC 3838,NGC 4452 NGC 4551） -- galaxies： kinematics and dynamics -- galaxies： structure -- methods： numerical

Robust fiber-based frequency synchronization system immune to strong temperature fluctuation

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Chinese Optics Letters 2018年第1期16卷 25-29页

作者：朱玺王波郭倚辰袁一博 Romeo Gamatham Bruce Wallace Keith Grainge Lijun Wang State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision Instrument Tsinghua University Department of Physics Tsinghua University SKA South Africa Blend on Baker jodrell bank centre for astrophysics Alan Turing Building School of Physics & AstronomyThe University of Manchester

In order to make the fiber-based frequency synchronization system suitable for the use of large-scale scientific and engineering projects in which the ambient temperature of the fiber links change dramatically, we design a non-harmonic frequency dissemination system immune to strong temperature fluctuation. After the lab tests, in which the ambient temperature of the fiber fluctuates 40°C/day and 20°C/h, respectively, the relative frequency stabilities of this system reaches 4.0 × 10-14∕s and 3.0 × 10-16∕104 s. It is demonstrated that the proposed non-harmonic scheme shows a strong robustness to complicated working environment with strong temperature fluctuation.

关键词： Diode lasers Fiber optic couplers Light beams Optical circulators Temperature Wavelength division multiplexers

Stellar Dynamical Modeling—Counting Conserved Quantities

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Research in Astronomy and astrophysics 2023年第5期23卷 198-212页

作者： Richard J.Long Shude Mao Yougang Wang Department of Astronomy Tsinghua UniversityBeijing 100084China jodrell bank centre for astrophysics Department of Physics and AstronomyThe University of ManchesterOxford RoadManchester M139PLUK National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China

Knowing the conserved quantities that a galaxy’s stellar orbits conform to is important in helping us understand the stellar distribution and structures within the galaxy.Isolating integrals of motion and resonances are particularly important,non-isolating integrals less so.We compare the behavior and results of two methods for counting the number of conserved quantities,one based on the correlation integral approach and the other a more recent method using machine learning.Both methods use stellar orbit trajectories in phase space as their only input,and we create such trajectories from theoretical spherical,axisymmetric,and triaxial model galaxies.The orbits have known isolating integrals and resonances.We find that neither method is fully effective in recovering the numbers of these quantities,nor in determining the number of non-isolating integrals.From a computer performance perspective,we find the correlation integral approach to be the faster.Determining the algebraic formulae of(multiple)conserved quantities from the trajectories has not been possible due to the lack of an appropriate symbolic regression capability.Notwithstanding the shortcomings we have noted,it may be that the methods are usable as part of a trajectory analysis tool kit.

关键词： galaxies kinematics and dynamics-methods numerical-galaxies structure

Studying infall in infrared dark clouds with multiple HCO+ transitions

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Research in Astronomy and astrophysics 2021年第8期 255-270页

作者：谢津津吴京文 Gary A.Fuller Nicolas Peretto 任致远陈龙飞闫耀庭李国栋段言夏季风王永雄李菂 National Astronomical Observatories Chinese Academy of Sciences Max-Planck-Institut für Radioastronomie NAOC-UKZN Computational astrophysics centre University of Kwa Zulu-Natal I.Physikalisches Institut University of Cologne School of Physics & Astronomy Cardiff University University of Chinese Academy of Sciences jodrell bank centre for astrophysics Department of Physics & Astronomy The University of Manchester

We investigate the infall properties in a sample of 11 infrared dark clouds（IRDCs） showing blue-asymmetry signatures in HCOJ=1-0 line profiles.We used JCMT to conduct mapping observations in HCOJ=4-3 as well as single-point observations in HCOJ=3-2,towards 23 clumps in these IRDCs.We applied the HILL model to fit these observations and derived infall velocities in the range of 0.5-2.7 km s,with a median value of 1.0 km s,and obtained mass accretion rates of 0.5-14 ×10Mo yr.These values are comparable to those found in massive star forming clumps in later evolutionary stages.These IRDC clumps are more likely to form star clusters.HCO+J=3-2 and HCO+J=1-0 were shown to trace infall signatures well in these IRDCs with comparable inferred properties.HCO+J=4-3,on the other hand,exhibits infall signatures only in a few very massive clumps,due to smaller opacities.No obvious correlation for these clumps was found between infall velocity and the NH3/CCS ratio.

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The TMRT K band observations towards 26 infrared dark clouds:NH_3, CCS, and HC_3N

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Science China(Physics,Mechanics & Astronomy) 2021年第7期64卷 126-136页

作者： Jinjin Xie Gary A.Fuller Di Li Longfei Chen Zhiyuan Ren Jingwen Wu Yan Duan Junzhi Wang Juan Li Nicolas Peretto Tie Liu Zhiqiang Shen National Astronomical Observatories Chinese Academy of SciencesBeijing100101China University of Chinese Academy of Sciences Beijing100049China jodrell bank centre for astrophysics Department of Physics and AstronomyUniversity of ManchesterManchesterM139PLUK Intituto de Astrofísica de Andalucia(CSIC) Granada18008Spain I.Physikalisches Institute University of CologneKöln50937Germany NAOC-UKZN Computational astrophysics centre University of KwaZulu-NatalDurban4000South Africa Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai200030China School of Physics&Astronomy Cardiff UniversityCardiffCF243AAUnited Kingdom

We present one of the first Shanghai Tian Ma Radio Telescope (TMRT) K Band observations towards a sample of 26 infrared dark clouds (IRDCs).We observed the (1,1),(2,2),(3,3),and (4,4) transitions of NH_(3) together with CCS (2_(1)–>1_(0)) and HC_(3)NJ=2-1,simultaneously.The survey dramatically increases the existing CCS-detected IRDC sample from 8 to 23,enabling a better statistical study of the ratios of carbon-chain molecules (CCM) to N-bearing molecules in IRDCs.With the newly developed hyperfine group ratio (HFGR) method of fitting NH_(3) inversion lines,we found the gas temperature to be between 10 and18 K.The column density ratios of CCS to NH_(3) for most of the IRDCs are less than 10^(-2),distinguishing IRDCs from low-mass star-forming regions.We carried out chemical evolution simulations based on a three-phase chemical model NAUTILUS.Our measurements of the column density ratios between CCM and NH_(3) are consistent with chemical evolutionary ages of 10^(5) yr in the models.Comparisons of the data and chemical models suggest that CCS,HC_(3)N,and NH_(3) are sensitive to the chemical evolutionary stages of the sources.

关键词： star formation infrared dark clouds chemical evolution

Alignment between galaxies and large-scale structure

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Chinese Journal of Astronomy and astrophysics 2009年第1期9卷 41-58页

作者： A. Faltenbacher Cheng Li Simon D. M. White Yi-Peng Jing Shu-De Mao Jie Wang Max-Planck-Institute for astrophysics Karl-Schwarzschild-Str. 1 D-85741 Garching Germany MPA/SHAO Joint Center for Astrophysical Cosmology at Shanghai Astronomical Observatory Shanghai 200030 China jodrell bank centre for Astrophysl＇cs Alan Turing Building The University of Manchester Manchester M13 9PL UK Department of Physics Institute of Computational Cosmology University of Durham Science Laboratories South Road Durham DH1 3LE UK

Based on the Sloan Digital Sky Survey DR6 （SDSS） and the ＇Millennium Simulation （MS）, we investigate the alignment between galaxies and large-scale structure. For this purpose, we develop two new statistical tools, namely the alignment correlation function and the cos（20）-statistic. The former is a two-dimensional extension of the traditional two-point correlation function and the latter is related to the ellipticity correlation function used for cosmic shear measurements. Both are based on the cross correlation between a sample of galaxies with orientations and a reference sample which represents the large-scale structure. We apply the new statistics to the SDSS galaxy catalog. The alignment correlation function reveals an overabundance of reference galaxies along the major axes of red, luminous （L 〉～L＊） galaxies out to projected separations of 60 h-lMpc. The signal increases with central galaxy luminosity. No alignment signal is detected for blue galaxies. The cos（2θ）-statistic yields very similar results. Starting from a MS semi-analytic galaxy catalog, we assign an orientation to each red, luminous and central galaxy, based on that of the central region of the host halo （with size similar to that of the stellar galaxy）. As an alternative, we use the orientation of the host halo itself. We find a mean projected misalignment between a halo and its central region of -25°. The misalignment decreases slightly with increasing luminosity of the central galaxy. Using the orientations and luminosities of the semi-analytic galaxies, we repeat our alignment analysis on mock surveys of the MS. Agreement with the SDSS results is good if the central orientations are used. Predictions using the halo orientations as proxies for cen- tral galaxy orientations overestimate the observed alignment by more than a factor of 2. Finally, the large volume of the MS allows us to generate a two-dimensional map of the alignment correlation function, which shows the reference galaxy distribution to be flat- tened parallel to the orientat

关键词： dark matter halos clustering-galaxies large-scale structure of Universe- cosmology theory -dark matter

Growth of Black Holes and Their Host Spheroids in (Sub)mm-loud High-Redshift QSOs

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Chinese Journal of Astronomy and astrophysics 2008年第1期8卷 12-24页

作者： Cai-Na Hao Xiao-Yang Xia Shu-De Mao Zu-Gan Deng Hong Wu Tianjin astrophysics Center Tianjin Normal University Tianjin 300384 National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 Institute of Astronomy University of Cambridge Madingley Road Cambridge CB3 0HA UK jodrell bank Observatory University of Manchester Macclesfield Cheshire SK11 9DL UK Graduate School of Chinese Academy of Sciences Beijing 100049

We study the growth of black holes and stellar population in spheroids at high redshift using several （sub）mm-loud QSO samples. Applying the same criteria established in an earlier work, we find that, similar to IR QSOs at low redshift, the far-infrared emission of these （sub）mm-loud QSOs mainly originates from dust heated by starbursts. By combining low-z IR QSOs and high-z （sub）mm-loud QSOs, we find a trend that the star formation rate （M＊） increases with the accretion rate （Mace）. We compare the values of M＊/Macc for submm emitting galaxies （SMGs）, far-infrared ultraluminous/hypeduminous QSOs and typical QSOs, and construct a likely evolution scenario for these objects. The （sub）mm-loud QSO transition phase has both high Macc and M＊ and hence is important for establishing the correlation between the masses of black holes and spheroids.

关键词： galaxies active - galaxies evolution - galaxies high-redshift - galaxies interactions - quasars general - galaxies starburst