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Bayesian analysis of galaxy spectral energy distributions with BayeSED

Proceedings of the International Astronomical Union 2013年第S295期8卷 312-312页

作者： Yunkun Han Zhanwen Han National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences 100012 Beijing China email: hanyk@*** Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 650011 Kunming China email: zhanwenhan@***

In Han & Han (2012), we have preliminarily built BayeSED and applied it to a sample of hyperluminous infrared galaxies. The physically reasonable results obtained from Bayesian model comparison and parameter estimation show that BayeSED could be a useful tool for understanding the nature of complex systems, such as dust obscured starburst-AGN composite galaxies, from decoding their complex SEDs. In this contribution, we present a more rigorous test of BayeSED by making a mock catalog from model SEDs with the value of all parameters to be known in advance.

关键词： galaxies: active galaxies: ISM methods: data analysis methods: statistical

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Photometric analysis of a blue straggler eclipsing binary in the old open cluster NGC 2141

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Science China(Physics,Mechanics & Astronomy) 2012年第8期55卷 1500-1504页

作者： LUO YangPing WANG Bo CHEN HaiLiang ZHANG XiaoBin HAN ZhanWen National Astronomical Observatories/Yunnan ObservatolT Chinese Academy of Sciences Kunming 650011 China Key blboratory.for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

To understand the formation mechanism of blue stragglers in open clusters, we conducted a photometric analysis for a blue straggler eclipsing binary in the old open cluster NGC 2141. By using the least square fitting of times of minima, we derived the ephemeris and redetermined the orbital period of this system to be 0.6227 d. We have also done a photometric analysis for light curve with the Wilson-Devinney Code （2003）. The photometric solutions reveal a semi-detached binary with the second- ary component filling its Roche lobe. The photometric mass ratio MJMI （secondary/primary） was determined to be 0.190_＋0.002 and the ratio of V-band luminosity L2/LI（V） is about 0.033_＋0.001, which indicates the secondary component is overluminous. Thus, this blue straggler likely results from a substantial mass exchange between these two components.

关键词： open cluster eclipsing binary blue straggler photometry

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A newly discovered active contact binary in the field of NGC 1348

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Research in Astronomy and Astrophysics 2012年第1期12卷 93-103页

作者： Xiang-Song Fang Sheng-Hong Gu Ho-Keung Hui Chi-Tai Kwok Bill Yeung Kam-Cheung Leung National Astronomical Observatories / Yunnan Observatory Chinese Academy of SciencesKunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Hokoon Nature Education cum Astronomical Centre Sik Sik-Yuen Hong Kong China Hong Kong Astronomical Society Hong Kong China

We present a CCD photometry study of a newly discovered active eclipsing binary in the field of open cluster NGC 1348 based on the first time-series photometric observation. From the minimum times, we determined an orbital period of P = 0.691363 d. Among our datasets, the BV（.RI）c light curves obtained in November 2008 were analyzed using the Wilson-Devinney light curve modeling tech- nique. Because of the uncertainty of the membership of this binary in open cluster NGC 1348, we have analyzed the photometric data in two cases with different primary effective temperatures： Case A （T1 = 7750K） and Case B （T1 = 5250K）. Our anal- yses reveal that, for Case A, it is a deep （f 〉 70%）, very low mass ratio （q - 0.096） binary system, indicating that it is now in the late evolution stage of a contact binary; while for Case B, it is a red system with extraordinarily long orbital period with respect to the period-color relation for normal contact binaries, which suggests that this binary has evolved off the main sequence. The well known O＇Connell effect （e.g., AB 0.03 mag） was found in the dataset obtained in November 2008, which could be due to the existence of starspots on the components, therefore the corresponding spot properties （for Case A： hot spot; for Case B： dark spot） were determined using the Wilson-Devinney code. With the purpose of analyzing the dark spot activity for Case B, we compared the light curves derived in different observing runs, and found that a slight change appeared from November to December, 2008, which indicates the evolution of spot activity on at least one component over a time scale of about one month.

关键词： stars： binaries： close -- stars： binaries： eclipsing -- stars： spots

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ERRATUM: 'A 1mm SPECTRAL LINE SURVEY TOWARD GLIMPSE EXTENDED GREEN objects (EGOs)' (2012, ApJS, 202, 1)

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The Astrophysical Journal Supplement Series 2013年第2期205卷

作者： J. H. He S. Takahashi X. Chen Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Astronomical Observatory/National Astronomical Observatory Chinese Academy of Sciences P.O. Box 110 Kunming 650011 Yunnan Province PR China Academia Sinica Institute of Astronomy and Astrophysics P.O. Box 23-141 Taipei 10617 Taiwan Key Laboratory for Research in Galaxies and Cosmology Key Laboratory of Radio Astronomy Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai 200030 PR China

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Proceedings of the International Astronomical Union 2013年第S292期8卷 103-103页

作者： J. H. He S. Takahashi X. Chen Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Astronomical Observatory/National Astronomical Observatory Chinese Academy of Sciences P.O. Box 110 Kunming 650011 Yunnan Province PR China email: jinhuahe@*** Academia Sinica Institute of Astronomy and Astrophysics P.O. Box 23-141 Taipei 10617 Key Laboratory for Research in Galaxies and Cosmology Key Laboratory of Radio Astronomy Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai 200030 PR China

EGOs are candidates of massive star forming regions that show signatures of outflows. A 1.1mm line survey has been performed to 89 EGOs using the AROSMT. Our high detection rates of H13CO+ 3-2 and SiO 6-5 lines support EGOs to be dense clouds harboring *** line luminosity linear correlations are found among different kinds of tracer lines: dense gas tracer H13CO+ 3-2, outflow tracer SiO 6-5, mixed dense gas and outflow tracers SO3Σ 65 − 54 and CH3OH lines, and relatively lower density gas tracers 12CO, 13CO, C18O 1-0 (see an example in Fig. 1). This can be explained if a universal similarity of density and thermal structures and probably of shock properties among all these EGO clouds are assumed. Furthermore, the outflow shocks are also required to be produced mainly inside of the natal clouds of the *** data scatter of the luminosity (and line width) correlations show a clear trend of worsening across larger cloud substructure size scales or toward larger cloud sizes, which demonstrates the growth of randomness in cloud structures and velocity fields. See more details in our paper (He et al. 2012).

关键词： turbulence — stars: formation — ISM: clouds — ISM: jets and outflows — ISM: kinematics and dynamics — radio lines: ISM

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GRB PROMPT EMISSION: TURBULENCE, MAGNETIC FIELD AND JITTER RADIATION

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International Journal of Modern Physics: Conference Series 2012年第8期ijmpcs卷 231-234页

作者： JIRONG MAO Korea Astronomy and Space Science Institute 776 Daedeokdae-ro Yuseong-gu Daejeon 305-348 Republic of Korea Yunnan Observatory Chinese Academy of Sciences Kunming Yunnan Province 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming China

The jitter radiation, which is the emission of relativistic electrons in the random and small-scale magnetic field, is utilized to investigate the high-energy emission of gamma-ray bursts. We produce the random and small-scale magnetic field using turbulent scenario. The electrons can be accelerated by stochastic acceleration. We also estimate the acceleration and cooling timescales, aiming to identify the validation of jitter regime under the GRB fireball framework. The possible maximum energy of electrons in our case is estimated as well.

关键词： acceleration of particles gamma rays: general radiation mechanisms: non-thermal

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Origin of power-law X-ray emission in the steep power-law state of X-ray binaries

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Research in Astronomy and Astrophysics 2011年第6期11卷 631-636页

作者： Li-Hong Yan Jian-Cheng Wang Yunnan Observatory /National Astronomical Observatories Key Laboratory for the Structure and Evolution of Celestial ObjectsChinese Academy of SciencesKunming 650011China Graduate School of Chinese Academy of Sciences Beijing 100049China

We present a new explanation for the origin of the steep power-law（SPL） state of X-ray *** power-law component of X-ray emission is the synchrotron radiation of relativistic electrons in highly magnetized compact spots orbiting near the inner stable circular orbit of a black *** has a hard spectrum that extends to above MeV energies,which is determined by the electron acceleration *** photons are then down-scattered by the surrounding plasma to form an observed steep *** discuss the relevance of the model to high-frequency quasi-periodic oscillations and the extremely high luminosity of the SPL state.

关键词： accretion accretion disks-black hole physics-radiation mechanisms：nonthermal-X-rays：binaries

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Chemical mixing by turbulent convection in the overshooting region below the convective envelope of RGB stars

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Research in Astronomy and Astrophysics 2011年第11期11卷 1351-1370页

作者： Xiang-Jun Lai Yan Li National Astronomical Observatories / Yunnan Observatory Chinese Academy of SciencesKunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy ofSciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

Based on the turbulent convection model （TCM）, we investigate chemical mixing in the bottom overshooting region of the convective envelope of intermediatemass stars, focusing on its influence on the formation and extension of blue loops in the Hertzsprung-Russell （HR） diagram. A diffusive mixing model is adopted during the Red Giant Branch （RGB） phase. The properties of the blue loop are changed by modification of the element profiles above the H-burning shell, which results from the incomplete mixing in the bottom overshooting region when the stellar model evolves up along the RGB. Such modification of the element profiles will lead to an increase of opacity in the region just above the H-burning shell and a decrease of opacity in the outer homogeneous convection zone, which will result in a quick decrease of the H-shell nuclear luminosity LH when the stellar model evolves from the RGB tip to its bottom and, finally, a much weaker and smaller convection zone will be obtained in the stellar envelope. This helps to form a longer blue loop. The extension of the blue loop is very sensitive to the parameters （Cx and αTCM） of the diffusive mixing model and of the TCM. The results mainly show that： 1） comparing the results of the classical model with the mixing-length theory, the lengths of the obtained blue loops with different combinations of the values of Cx and αTCM are all increased and the length of the blue loop increases with the values of parameters Cx and αTCM; 2） the diffusive mixing model can significantly extend the time of stellar models lingering on the blue side of the HR diagram, even though the length of the blue loop for the 7M⊙ star has a less prominent difference between the classical and diffusive mixing model; 3） both the observations referring to the location of the Cepheid instability strip and the number ratio NB/NR of blue to red evolved stars in the Galactic open clusters can confine the two parameters in a range of 0.5 ≤ αLTCM ≤ 0.9 and 10-5 ≤

关键词： stars convection-star interiors-star HR diagram-blue loops-Cepheids-Galactic open clusters

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External photon fields in Fermi bright blazars

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Research in Astronomy and Astrophysics 2011年第8期11卷 902-908页

作者： Xiao-Yan Gao Jian-Cheng Wang Ming Zhou National Astronomical Observatories / Yunnan Observatories Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

The external Compton （EC） model is used to study the high energy emission of some blazars, in which the external photon field is considered to dominate inverse Compton radiation. We explore the properties of the external photon field through analyzing the FERMI LAT bright AGN sample within three months of the start of operations in sky-survey mode. In the sample, assuming the high energy radiation of low synchrotron peaked blazars is from the EC process, we find that the external photon parameter Uext/υext may not be a constant. Calculating synchrotron and inverse Compton luminosity from the quasi-simultaneous broadband spectral energy distributions, we find that they have an approximately linear relation. This indicates that the ratio of external photon and magnetic energy density is a constant in the comoving frame, implying that the Lorentz factor of the emitting blob depends on the external photon field and magnetic field. The result gives a strong constraint on the dynamic jet model.

关键词： galaxies： active -- galaxies： jets -- gamma-rays： galaxies --- radiationmechanism： non-thermal

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Stellar kinematics and populations out to 1.5 effective radii in the elliptical galaxy NGC 4636

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Research in Astronomy and Astrophysics 2011年第8期11卷 909-923页

作者： Shi-Bi PU Zhan-Wen Han National Astronomical Observatory/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China

We present high quality long slit spectra along the major and minor axes out to 1.5 effective radii of the massive galaxy NGC 4636 taken by the Hobby-Eberly Telescope. Using the Fourier Correlation Quotient method, we measured the stellar line-of-sight velocity distribution along the axes. Furthermore, six Lick/IDS indices （Hβ, Mgb, Fe5015, Fe5270, Fe5335, Fe5406） are derived from the clean spectrum. By comparing the measured absorption line strengths with the predictions of Simple Stellar Population （SSP） models, we derived ages, total metallicity and a abundance profiles of the galaxy. This galaxy presents old and [α/Fe] overabundant stellar populations. Indeed, using the SSP model, we obtained the broadband color profiles. The theoretical colors match well with the measured colors and present red sharp peaks at the galaxy center. The sharp peaks of the colors are mainly shaped by the high metallicity in the galaxy＇s center. Interestingly, the galaxy has steep negative metaUicity gradients, but the trend flattens outwards. This result likely suggests that the center and outer regions of the galaxy formed through different formation processes.

关键词： galaxy： elliptical and lenticular -- galaxy： abundances -- galaxy： kine- matic and dynamics -- galaxy： individual （NGC 4636）

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