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Kinematic and chemical properties of five open clusters based on SDSS DR7

Research in Astronomy and Astrophysics 2010年第8期10卷 761-776页

作者： Xin-Hua Gao Li Chen key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China Graduate University of Chinese Academy of Sciences Beijing 100049 China key Laboratory for Astrophysics Shanghai 200234 China

We present metallicities and radial velocities for five old open clusters （NGC 6791, NGC 2420, NGC 2682, NGC 2158, and NGC 7789） using data from the seventh public data release of the Sloan Digital Sky Survey （SDSS）, which includes the directed stellar program SEGUE： Sloan Extension For Galactic Understanding and Exploration. The radial velocities are used to calculate cluster membership probabilities for stars in each cluster region. NGC 6791, NGC 2420, NGC 2682, NGC 2158 and NGC 7789 are found to have mean metallicities [Fe/H]= ＋0.08 ± 0.09, -0.38± 0.11, -0.08±0.05, -0.41 ±0.13 and -0.19 ± 0.13 dex （s.d.）, respectively. The mean radial velocities for NGC 6791, NGC 2420, NGC 2682, NGC 2158 and NGC 7789 are Vr = -45.9 ± 0.2, ＋76.1 ± 0.2, ＋35.0 ± 0.2, ＋26.9 ± 0.2 and -48.2± 0.2 km s^-1（s.e.m.）, respectively. We have compared our results with the values from literatures, and found that our metallicity of NGC 6791 is significantly underestimated （by about 0.3 dex） and our radial velocities of the open clusters agree well with the values derived using high-resolution spectroscopy.

关键词： open clusters and associations general -- open clusters and associations individual (NGC 6791, NGC 2420, NGC 2682, NGC 2158, NGC 7789)

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A computational method to help identify and measure metallines in high resolution QSO spectra

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Research in Astronomy and Astrophysics 2011年第11期11卷 1279-1297页

作者： Xi-Heng Shi David Tytler Jin-Liang Hou David Kirkmant Jeffery Lee Benjamin Ou key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical ObservatoryChinese Academy of Sciences Shanghai 200030 China Center for Astrophysics and Space Sciences University of California San Diego La Jolla CA92093-0424 USA

A computational code is developed to help identify metal absorption lines in high resolution QSO spectra, especially in the Lyα forest. The input to the code includes a list of line central wavelengths, column densities and Doppler widths. The code then searches for candidate metal absorption systems and assesses the probability that each system could be real. The framework of the strategy we employ is described in detail and we discuss how to estimate the errors in line profile fitting that are essential to identification. A series of artificial spectra is constructed to calibrate the performance of the code. Due to the effects of blending and noise on Voigt profile fitting, the completeness of the identification depends on the column density of absorbers. For intermediate and strong artificial metal absorbers, more than 90% could be confirmed by the code. The results of applying the code to the real spectra of QSOs HS0757＋5218 and Q0100＋1300 are also presented.

关键词： methods data analysis-quasars absorption lines-quasars individual(HS0757+5218, Q0100+1300)

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The LEGUE disk targets for LAMOST's pilot survey

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Research in Astronomy and Astrophysics 2012年第7期12卷 805-812页

作者： Li Chen Jin-Liang Hou Jin-Cheng Yu Chao Liu Li-Cai Deng Heidi Jo Newberg Jeffrey L. Carlin Fan Yang Yue-Yang Zhang Shi-Yin Shen Hao-Tong Zhang Jian-Jun Chen Yu-Qin Chen Norbert Christlieb Zhan-Wen Han Hsu-Tai Lee Xiao-Wei Liu Kai-Ke Pan Jian-Rong Shi Hong-Chi Wang Zi Zhu key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical ObservatoryChinese Academy of Sciences Shanghai 200030 Chinat key Lab for Optical Astronomy National Astronomical Observatories Chinese Academy ofSciences Beijing 100012 China Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute 1108th Street Troy NY 12180 USA Center for Astronomy University of Heidelberg Landessternwarte K6nigstuhl 12 D-69117Heidelberg Germany Yunnan Astronomical Observatory Chinese Academy of Sciences Kunming 650011 China Institute of Astronomy and Astrophysics Academia Sinica E O. Box 23-141 Taipei 106 China Department of Astronomy & Kavli Institute of Astronomy and Astrophysics Peking UniversityBeiiing 100875 China Apache Point Observatory PO Box 59 Sunspot NM 88349 USA Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China School of Astronomy and Space Science Nanjing University Nanjing 210008 China

We describe the target selection algorithm for the low latitude disk por- tion of the LAMOST Pilot Survey, which aims to test systems in preparation for the LAMOST spectroscopic survey. We use the PPMXL astrometric catalog, which provides positions, proper motions, B/R/I magnitudes （mostly） from USNO-B and d/H/Ks from the Two Micron All Sky Survey （2MASS） as well. We chose eight plates along the Galactic plane, in the region 0° 〈 α° 〈 67° and 42° 〈 δ 〈 59°, which cover 22 known open clusters with a range of ages. Adjacent plates may have some small overlapping area. Each plate covers an area of 2.5° in radius, with its cen- tral star （for the Shack-Hartmann guider） brighter than 8th magnitude. For each plate, we create an input catalog in the magnitude range 11.3 〈 Imag 〈 16.3 and Bmag available from PPMXL. The stars are selected to satisfy the requirements of the fiber positioning system and have a uniform distribution in the I vs. B - I color-magnitude diagram. Our final input catalog consists of 12 000 objects on each of eight plates that are observable during the winter observing season from the Xinglong Station of the National Astronomical Observatory of China.

关键词： disk: Milky Way - stars: spectroscopy -- survey: pilot

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