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Studying dynamical models of the core galaxy NGC 1399 with merging remnants

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Research in Astronomy and Astrophysics 2018年第12期18卷 95-104页

作者： Li-Chin Yeh Ing-Guey Jiang Institute of Computational and Modeling Science National Tsing-Hua University Department of Physics and Institute of Astronomy National Tsing-Hua University

An investigation on the possible dynamical models of the core galaxy NGC 1399 is performed.Because early-type galaxies are likely to be formed through merging events, remnant rings are considered in the modeling process.A numerical survey over three parameters is employed to obtain the best-fit models that are completely consistent with observations.It is found that the inner slope of the dark matter profile is cuspy for this core galaxy.The existence of remnant rings in best-fit models indicates a merging history.The remnant ring explains the flattened surface brightness and thus could be the physical counterpart of the core structure of NGC 1399.

关键词： galaxies:kinematics and dynamics galaxies:elliptical and lenticular,cD galaxies:formation

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

Stability of the coplanar planetary four-body system

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Research in Astronomy and Astrophysics 2020年第9期20卷 228-240页

作者： Chao Liu Sheng-Ping Gong Jun-Feng Li School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

We consider the coplanar planetary four-body problem,where three planets orbit a large star without the cross of their orbits.The system is stable if there is no exchange or cross of orbits.Starting from the Sundman inequality,the equation of the kinematical boundaries is derived.We discuss a reasonable situation,where two planets with known orbits are more massive than the third one.The boundaries of possible motions are controlled by the parameter c^2E.If the actual value of c^2E is less than or equal to a critical value(c^2 E)cr,then the regions of possible motions are bounded and therefore the system is stable.The criteria obtained in special cases are applied to the Solar System and the currently known extrasolar planetary systems.Our results are checked using N-body integrator.

关键词： methods:analytical methods:numerical celestial mechanics planets and satellites:dynamical evolution and stability stars:kinematics and dynamics galaxies:kinematics and dynamics

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

Forecasts of cosmological constraints from HI intensity mapping with FAST,BINGO and SKA-I

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Research in Astronomy and Astrophysics 2019年第12期19卷 343-360页

作者： Elimboto Yohana Yi-Chao Li Yin-Zhe Ma Astrophysics and Cosmology Research Unit School of MathematicsStatistics&Computer ScienceUniversity of KwaZulu-NatalWestville CampusPrivate Bag X54001Durban4000South Africa Dar Es Salaam University College of Education A Constituent College of the University of Dar Es SalaamP.O.Box 2329 Dar Es SalaamTanzania Astrophysics and Cosmology Research Unit School of Chemistry and PhysicsUniversity of KwaZulu-NatalWestville CampusPrivate Bag X54001Durban4000South Africa NAOC-UKZN Computational Astrophysics Centre(NUCAC) University of KwaZulu-NatalDurban4000South Africa

We forecast the cosmological constraints of the neutral hydrogen(HI) intensity mapping(IM)technique with radio telescopes by assuming 1-year of observational time. The current and future radio telescopes that we consider here are Five-hundred-meter Aperture Spherical radio Telescope(FAST), Baryon acoustic oscillations In Neutral Gas Observations(BINGO), and Square Kilometre Array phase Ⅰ(SKA-Ⅰ) single-dish experiments. We also forecast the combined constraints of the three radio telescopes with Planck. We find that the 1σ errors of(w0, wa) for BINGO, FAST and SKA-Ⅰ with respect to the fiducial values are respectively,(0.9293, 3.5792),(0.4083, 1.5878) and(0.3158, 0.4622). This is equivalent to(56.04%, 55.64%) and(66.02%, 87.09%) improvements in constraining(w0, wa) for FAST and SKA-Ⅰ respectively relative to BINGO. Simulations further show that SKA-Ⅰ will put more stringent constraints than both FAST and BINGO when each of the experiments is combined with Planck measurements. The 1σ errors for(w0, wa), BINGO + Planck, FAST + Planck and SKA-Ⅰ + Planck covariance matrices are respectively(0.0832, 0.3520),(0.0791, 0.3313) and(0.0678, 0.2679) implying there is an improvement in(w0, wa) constraints of(4.93%, 5.88%) for FAST + Planck relative to BINGO + Planck and an improvement of(18.51%, 23.89%) in constraining(w0, wa) for SKA-Ⅰ + Planck relative to BINGO + Planck. We also compared the performance of Planck data plus each single-dish experiment relative to Planck alone,and find that the reduction in(w0, wa) 1σ errors for each experiment plus Planck, respectively, imply the(w0, wa) constraints improvement of(22.96%, 8.45%),(26.76%, 13.84%) and(37.22%, 30.33%) for BINGO + Planck, FAST + Planck and SKA-Ⅰ + Planck relative to Planck alone. For the nine cosmological parameters in consideration, we find that there is a trade-off between SKA-Ⅰ and FAST in constraining cosmological parameters, with each experiment being more superior in constraining a particular set of parameters.

关键词： surveys galaxies:statistics cosmology:observations large-scale structure of Universe galaxies:kinematics and dynamics