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Stellar X-ray Sources in the Rosette Nebula

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Chinese Journal of Astronomy and Astrophysics 2004年第2期4卷 153-165页

作者： W.P.Chen P.S.Chiang J.Z.Li Institute of Astronomy National Central UniversityChung-Li 32054Taiwan National Astronomical Observatories Chinese Academy of SciencesBeijing 100012

We present optical photometric and spectroscopic studies of ROSAT X-ray stellar sources in the Rosette Nebula star-forming region. The brightest X-ray sources are either massive stars or active T Tauri stars associated with the open cluster NGC 2244, or are foreground stars. Some of the spectra of the young stars newly identified in the region are presented.

关键词： stars: early-type stars: pre-main sequence stars: formation HII regions

Near-Infrared Observations of the Massive Star Forming Region IRAS 23151+5912

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Chinese Journal of Astronomy and Astrophysics 2004年第3期4卷 284-298页

作者： Xue-Peng Chen Yong-Qiang Yao Purple Mountain Observatory Chinese Academy of Sciences, Nanjing 210008 Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008

Near-infrared images and K-band spectroscopy of the massive star-formingregion IRAS 23151+5912 are presented. The JHK′ images reveal an embedded infrared clusterassociated with infrared nebula, and the H_2 (2.12 μm) narrowband image provides for the first timeevidence of outflow activity associated with the cluster. That the cluster is young can be shown bythe high percentage of infrared excess sources and the outflow activity. We suggest an age of thecluster of ～ 10~6 yr. Eight young stars are found in the bright nebular core around IRAS23151+5912. By the color-magnitude diagrams of the cluster, we found five high-mass YSOs and fourintermediate-mass YSOs in the cluster. Eight H_2 emission features are discovered in the region witha scattered and non-axisymmetric distribution, indicating the existence of multiple outflows drivenby the cluster. Diffuse H_2 emission detected to the north and to the west of the cluster mayresult from UV leakage of the cluster. Brγ, H_2, and CIV emission lines are found in the K-bandspectrum of the brightest source, NIRS 19, indicating the presence of envelope, stellar wind, andshock in the circumstellar environment. We have estimated an O7-O9 spectral type for the centralmassive YSO (20 ～ 30 solar mass), with an age of less than 1 x 10~6 yr.

关键词： infrared radiation stars: formation ISM: individual: IRAS 23151 + 5912 ISM: jets and outflows

SMA molecular line survey towards the massive star-forming region G10.6-0.4in W31complex

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Research in Astronomy and Astrophysics 2018年第11期18卷 29-42页

作者： Wai-Ho Wong Tao An Key Laboratory of Radio Astronomy Shanghai Astronomical ObservatoryChinese Academy of SciencesShanghai 200030China University of Chinese Academy of Sciences Beijing 100049China

Line surveys of complex molecules with millimeter and sub-millimeter telescopes are important for probing the physical and chemical environments of massive star forming regions(MSFRs).We present a molecular line survey with the Submillimeter Array(SMA) in the frequency ranges of 220.3–222.3 GHz and 230.3–232.3 GHz toward G10.6-0.4, the brightest star forming core in the W31 complex. Ninety-nine transitions from 22 molecular species and their isotopologues are identified. The moment 0 images of typical molecules show a compact core which is concentrated at the continuum peak position. Based on the local thermodynamic equilibrium assumption, the molecular line data are modeled. The rotational temperatures of those molecular species range from 96 to 178 K and their column densities range from 2.0×1014to 3.7×1017cm-2. The observational data suggest that all complex molecules are located in a warm environment. Chemical environments of the molecules are discussed. We compared molecular abundances and gas temperatures in G10.6-0.4 with those in other MSFRs, and found that gas temperatures and fractional abundances of specific molecules in G10.6-0.4 are similar to the typical MSFR W51 North, suggesting that there are similar physical and chemical environments in these two MSFRs.

关键词： stars: formation ISM: abundances ISM: individual objects: G10.6-0.4 ISM: molecules radio lines: ISM

Statistical Properties of 6.7 GHz Methanol Maser Sources

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Chinese Journal of Astronomy and Astrophysics 2003年第1期3卷 49-68页

作者： YeXu Xing-WuZheng Dong-RongJiang NationalAstronomicalObservatories ChineseAcademyofSciencesUrumqi830011／／ShanghaiAstronomicalObservatoryChineseAcademyofSciencesShanghai200030 DepartmentofAstronomy NanjingUniversityNanjing210093 ShanghaiAstronomicalObservatory ChineseAcademyofSciencesShanghai200030

We present a statistical analysis of 482 6.7 GHz methanol maser sources from the available literature, on their maser emission and the characteristics of their associated infrared sources. On the color-color diagram, more than 70% of the objects fall within a very small region (0.57 ≤ [25-12] ≤ 1.30 and 1.30 ≤ [60-12] ≤ 2.50). This suggests that 6.7 GHz methanol maser emission occurs only within a very short evolutionary phase during the earliest stage of star formation. The velocity ranges of the masers belong to two main groups: one from 1 to 10 km s?1, and one from about 11 to 20 km s?1. These velocity ranges indicate that the masers are probably associated with both disks and outflows. The correlations between the maser and infrared flux densities, and between the maser and infrared luminosities, suggest that far-infrared radiation is a possible pumping mechanism for the masers which most probably originate from some outer molecular envelopes or disks.

关键词： masers ISM: molecules stars: circumstellar matter stars: formation ISM: HII regions

Evolutions of CH3CN abundance in molecular clumps

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Research in Astronomy and Astrophysics 2021年第8期21卷 247-254页

作者： Zhen-Zhen He Guang-Xing Li Chao Zhang Department of Astronomy Yunnan University 2. South-Western Institute For Astronomy Research Yunnan University

To investigate the effects of massive star evolution on surrounding molecules,we select nine massive clumps previously observed with the Atacama Pathfinder Experiment（APEX） telescope and the Submillimeter Array（SMA） *** on the observations of APEX,we obtain luminosity to mass ratios L/Mthat range from 10 to 154 L/M,where some of them embedded ultra compact（UC） H Ⅱ *** the SMA,CHCN（12-11） transitions were observed toward nine massive starforming *** derive the CHCN rotational temperature and column density using the XCLASS program,and calculate its fractional *** find that CHCN temperature seems to increase with the increase of L/Mwhen the ratio is between 10 to 40 L/M,then decrease when L/M≥ 40 L/*** that the CHCN gas is heated by radiation from the central star,the effective distance of CHCN relative to the central star is *** distance ranges from ～ 0.003 to ～ 0.083 pc,which accounts for ～ 1/100 to ～ 1/1000 of clump *** effective distance increases slightly as L/Mincreases(R～(L/M)).Overall,the CHCN abundance is found to decrease as the clumps evolve,e.g.,X～(L/M).The steady decline of CHCN abundance as the clumps evolution can be interpreted as a result of photodissociation.

关键词： line: identification stars: evolution stars: formation ISM: molecules submillimeter: ISM

Discovery of an Optical Jet in the Rosette Nebula: Rosette HH2

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Chinese Journal of Astronomy and Astrophysics 2003年第6期3卷 495-498页

作者： Jin-Zeng LiNational Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

We report on the discovery of an optical jet - Rosette HH2 - in the RosetteNebula. The jet system bears unique features for residing at the center of a giant HII region, andits energy source is visible with apparently very low extinction along the line of sight. Unlikemost other Herbig-Haro jets, this jet indicates a high-excitation origin, and its extended portionshows a seemingly intact structure, instead of normally a shocked working surface, which isattributed to photoablation.

关键词： stars: formation stars: pre-main sequence herbig-haro objects ISM: jetsand outflows

WISE Infrared Search for Young Stellar Objects Associated with Starless Cores

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International Journal of Astronomy and Astrophysics 2023年第2期13卷 89-111页

作者： Susumu Sato Yuri Iwamoto Yoichi Itoh Nishi-Harima Astronomical Observatory Center for Astronomy University of Hyogo Hyogo Japan

This study presents the results of an infrared search of young stellar objects (YSOs) associated with cores with high optical extinction and no associated infrared IRAS source. Four hundred YSO candidates were identified in the WISE photometric catalog based on the infrared excess attributed to the circumstellar materials and proto-planetary disks. One-hundred and forty-nine cores do not have YSO candidates. Whereas, 32 cores harbor only Class I candidates and 107 cores have Class II candidates. Ninety-one cores that were previously identified as starless cores, were found to contain YSOs. The ratio of the number of starless cores to the number of star-forming cores suggests that the typical timescale from molecular cloud core formation to the birth of a star is in the range of 0.5 - 1.4 Myr.

关键词： stars: formation ISM: Clouds Infrared: stars