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The Environment and Star Formation around the Infrared Bubble N 13

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Research in Astronomy and Astrophysics 2023年第1期23卷 108-120页

作者： Dong-Dong zhou jian-jun zhou Gang Wu Jarken Esimbek Ye Xu Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China Key Laboratory of Radio Astronomy Chinese Academy of SciencesUrumqi 830011China Xinjiang Key Laboratory of Radio Astrophysics Urumqi 830011China Max-Planck-Institut für Radioastronomie Auf dem Hügel 69D-53121 BonnGermany Purple Mountain Observatory Chinese Academy of SciencesNanjing 210033China

Infrared bubbles provide a unique opportunity to study the interactions between massive stars and surrounding *** conduct a multi-wavelength study on the environment and star formation around an infrared bubble *** dust clumps and two molecular clumps are identified around N 13,which are all distributed on the *** stellar objects(YSOs)are carefully searched using infrared colors and YSO candidates of WISE and Gaia DR2,and three Class I/II YSOs are found in N *** addition,four O-type stars identified in N 13 are probably the exciting *** dynamical and fragmentation ages of N 13 are 0.32-0.35 and 1.37-2.80 Myr respectively,which suggest that the radiation-driven implosion model may be dominant in N *** comparing the small-size bubble N 13(R~1.9 pc)and the larger-size bubble G15.684-0.29(R~15.7 pc)we found that star formation activity is more active in the large-size *** comparisons of ten bubbles show that small-size bubbles have a small ratio of kinetic age versus the fragmentation *** star formation may be more active in bubbles with larger ratio between kinetic and fragmentation ***,the collect and collapse mechanism may play the dominant role in the large-size ones.

关键词： ISM bubbles-ISM structure-ISM kinematics and dynamics-stars formation

1_(10)-1_(11) H_2CO and H_(110α) observations towards the giant HII region in cloud complex W43

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Research in Astronomy and Astrophysics 2011年第1期11卷 63-70页

作者： Gang Wu Jarken Esimbek jian-jun zhou Xiao-Hong Han National Astronomical Observatories / Urumqi Observatory Chinese Academy of SciencesUrumqi 830011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

The 110-111 formaldehyde （H2CO） absorption line and H110α radio recombination line （H RRL） are observed towards the giant HII region in cloud complex W43. The observations are obtained using the Nanshan 25 m single dish operated by Urumqi Observatory, National Astronomical Observatories of China. A region about 30 × 30 is observed, which covers the whole HII region in W43. Except for the central 10 region, all the other seven points are first observed with the H2CO 110-111 absorption. The column density of the H2CO is calculated, and the H2CO density contours show some differences with the infrared image. Multiple features appear in the H2CO and H RRL which indicate complex structure. The intensities of the H2CO and the velocities of the H110α seem to present a linear correlation, which illustrates that the sphere of influence of the central WR/OB cluster may be much more extended than presently known, since the size is nearly 50 pc.

关键词： ISM: radio lines -- HII regions -- stars: formation

Robust M-estimate of GJR Model with High Frequency Data

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Acta Mathematicae Applicatae Sinica 2015年第3期31卷 591-606页

作者： Jin-shan HUANG Wu-qing WU Zhao CHEN jian-jun zhou Department of Statistics and Finance University of Science and Technology of China School of Business Renmin University of China Princeton University Department of Statistics Yunnan University

In this paper, we study the GJR scaling model which embeds the intraday return processes into the daily GJR model and propose a class of robust M-estimates for it. The estimation procedures would be more efficient when high-frequency data is taken into the model. However, high-frequency data brings noises and outliers which may lead to big bias of the estimators. Therefore, robust estimates should be taken into consideration. Asymptotic results are derived from the robust M-estimates without the finite fourth moment of the innovations. A simulation study is carried out to assess the performance of the model and its *** M-estimate of GJR model is also applied in predicting Va R for real financial time series.

关键词： GJR model GARCH model Robust M-estimates scaling model volatility proxy

Measurements for the Performance of the Digital Autocorrelation Spectrometer

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Chinese Journal of Astronomy and Astrophysics 2007年第2期7卷 297-303页

作者： Fa-Chun Lu Jarken Esimbek jian-jun zhou Xing-Wu Zheng National Astronomical Observatories/Urumqi Observatory Chinese Academy of Sciences Urumqi830011 Graduate University of Chinese Academy of Sciences Beijing 100049 Department of Astronomy Nanjing University Nanjing 210093

Injecting phase calibration （PCAL） signals to the feed horn of the observation system and analyzing the output response signals of the spectrometer, we measured the working performance of a 4096-channel digital autocalibration spectrometer. The results demonstrate that the spectrometer has a fine working performance：（1） the channels are distributed uniformly in the spectrometer; （2） line drift produces little effect on the observation results; （3） spectral resolution shows little changes with observation time. The distribution of the frequency resolution in an 80 MHz bandwidth was measured. A trial observation on the two molecular spectral lines of H2CO and H110α taken with this spectrometer is described.

关键词： instrumentation spectrometer- ISM: molecules - radio lines ISM

Characteristics of infrared point sources associated with OH masers

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Research in Astronomy and Astrophysics 2010年第2期10卷 166-172页

作者： Ji-Mang Mu Jarken Esimbek jian-jun zhou Hai-Juan Zhang National Astronomical Observatories/Urumqi Observatory Chinese Academy of Sciences Urumqi 830011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

We collect 3249 OH maser sources from the literature published up to April 2007, and compile a new catalog of OH masers. We look for the exciting sources of these masers and their infrared properties from IRAS and MSX data, and make a sta- tistical study. MSX sources associated with stellar 1612 MHz OH masers are located mainly above the blackbody line; this is caused by the dust absorption of stellar en- velopes, especially in the MSX_A band. The mid-IR sources associated with stellar OH masers are concentrated in a small region in an [A]-[D] vs.[A]-[E] diagram with a small fraction of contamination; this gives us a new criterion to search for new stellar OH masers and distinguish stellar masers from unknown types of OH masers. IR sources associated with 1612 MHz stellar OH masers show an expected result： the average flux of sources with F60 〉 F25 increases with increasing wavelength, while those with F60 〈 F25 vary little with wavelength, because the sources with F60 〈 F25 are much hotter than those with F60 〉 F25.

关键词： masers: OH maser -- stars: late-type star -- catalog -- star-forming region -- infrared radiation

The comparison of H_2CO(1_(10)–1_(11)),C^(18)O(1–0) and the continuum towards molecular clouds

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Research in Astronomy and Astrophysics 2014年第8期14卷 959-970页

作者： Xin-Di Tang Jarken Esimbek jian-jun zhou Gang Wu Daniel Okoh Xinjiang Astronomical Observatory Chinese Academy of Sciences University of Chinese Academy of Sciences Key Laboratory of Radio Astronomy Chinese Academy of Sciences Physics & Astronomy Department University of Nigeria

We present large scale observations of C^18O （1-0） towards four massive star forming regions： MON R2, S156, DR17/L906 and M17/M18. The transitions of H2CO （110-111）, C^18O （1-0） and the 6cm continuum are compared in these four regions. Our analysis of the observations and the results of the Non-LTE model shows that the brightness temperature of the formaldehyde absorption line is strongest in a background continuum temperature range of about 3 - 8 K. The excitation of the H2CO absorption line is affected by strong background continuum emission. From a comparison of H2CO and C^18O maps, we found that the extent of H2CO absorption is broader than that of C^18O emission in the four regions. Except for the DR17 region, the maximum in H2CO absorption is located at the same position as the C^18O peak. A good correlation between intensities and widths of H2CO absorption and C^18O emission lines indicates that the H2CO absorption line can trace the dense, warm regions of a molecular cloud. We find that N（H2CO） is well correlated with N（ C^18O） in the four regions and that the average ratio of column densities is （N（H2CO）/N（ClSO））～0.03.

关键词： ISM clouds -- molecules -- stars formation

A kinematic study of the integral shaped filament:what roles do filaments play in forming young stellar clusters?

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Research in Astronomy and Astrophysics 2018年第7期18卷 37-44页

作者： Gang Wu Esimbek Jarken Willem Baan jian-jun zhou Dong-Dong zhou Xiao-Hong Han Aldiyar Agishev Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumuqi 830011China Key Laboratory of Radio Astronomy Chinese Academy of SciencesUrumqi 830011China University of Chinese Academy of Sciences Beijing 100049China Netherlands Institute for Radio Astronomy NL-7991 PD Dwingeloothe Netherlands Faculty of Physics and Technology A1-Farabi Kazakh National UniversityAlmaty050049Kazakhstan

Young protoclusters （embedded stellar clusters） are responsible for the vast majority of star formation currently occurring in the Galaxy. Recent observations suggest a scenario in which filamen-tary structures in the interstellar medium represent the first step towards precluster clumps and even- tually star formation. Whether filaments continuously fuel the star formation process when the cluster accretes material is still an open question. In this paper, we present a case study of the famous ＇integral shaped filament＇（ISF） in the Orion A molecular cloud and we seek to study the kinematics which is truly originated from the ISF. We firstly define the central ridge of the ISF with NHa, ^12CO, ^13CO and N2H^＋. Undulations are present in all the ridges. Moreover, a large scale offset is apparent in the ridges as derived by different tracers, which may be explained by the slingshot mechanism proposed by Stutz ＆ Gould. We fit the velocity field of the ISF and find the derived velocity gradient is about 0.7 km s^- 1 pc^- 1 which may come from an overall contraction. We propose a method to check the accretion flow along the ISF by using the velocity deviations of different molecular tracers, which is better than the common method of using the velocity distribution of one tracer alone. Using the velocity deviations, we also find that OMC-1 to 5 are located close to the local extrema of the fluctuations, which may demonstrate that gas flows toward each clump along the ISE

关键词： ISM clouds - ISM structure - ISM kinematics and dynamics - stars formation

Evidence of Evolution in the Dense Cores in Massive Star Forming Regions

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Chinese Journal of Astronomy and Astrophysics 2005年第4期5卷 363-370页

作者： jian-jun zhou Jarken Esimbek Ji-Xian Sun Bing-Gang Ju Jing-jiang Sun National Astronomical Observatories/Urumqi observatory Chinese Academy of SciencesUrumqi 830011 Graduate School of the Chinese Academy of Science Beijing 100080 Qinghai Station of Purple mountain Observatory Chinese Academy of Science DelinghaQinghai 817000

The excitation of H2O masers usually needs very high density gas,hence it can serve as a marker of dense gas in HⅡ region. We selected a sample of H2O maser sources from Plume et al. （four with, and four without detected CS（J = 7 - 6） emission）, and observed them in ^13CO（J=1-0） and C^18O （J=1-0）. C^18O （J=1-0） emission was detected only in three of the sources with detected CS（J=7-6） emission. An analysis combined with some data in the literature suggests that these dense cores may be located at different evolutionary stages. Multi-line observation study may provide us clues on the evolution of massive star forming regions and the massive stars themselves.

关键词： ISM: molecules - masers - radio lines: ISM-stars: formation

Investigation on the Structure and Performance of Polypropylene Sheets and Bi-axially Oriented Polypropylene Films for Capacitors

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Chinese Journal of Polymer Science 2022年第12期40卷 1688-1696,I0011页

作者： Chong Zhang Xi-Ying Dai Zhao-Liang Xing Shao-Wei Guo Fei Li Xin Chen jian-jun zhou Lin Li State Key Laboratory of Advanced Power Transmission Technology Global Energy Interconnection Research Institute Co.Ltd.Beijing 102209China Beijing Key Laboratory of Energy Conversion and Storage Materials College of ChemistryBeijing Normal UniversityBeijing 100875China

Polypropylene(PP) sheets are cast with various chill roll temperatures and rates, which are studied with differential scanning calorimetry, wide angel X-ray diffraction, scanning electronic microscopy and dielectric withstand voltage test system. The results show that increasing the chill roll temperature and cast rate can promote the increase of crystallinity and the growth of β-form. The PP sheets have asymmetric skin layer structures. The lower the chill roll temperature, the thicker the skin layer, the smaller the spherulite size. The electric breakdown strength(Eb) of PP sheets is mainly affected by the crystallinity but not the morphology. The PP sheets are further stretched to prepare bi-axially oriented PP(BOPP) films with various heat setting time. Our results indicate that the structure of PP sheets affects the properties of BOPP films. The as prepared BOPP films from the sheets cast at high chill roll temperature and rate have the highest crystallinity and Eb. Heat setting time has profound effect on the crystallinity and Eb, which increase first and then decrease with the heat setting time. It is expected that our study can provide guidance for optimizing process parameters.

关键词： BOPP film Polypropylene sheet Electric breakdown strength Crystallinity Heat set