2004, Vol.4, No.1 (February 20, 2004)


Contents

Invited Contribution
Cosmology
  • The Effect of Central Baryonic Cores in Dark Halos on the Evaluation of Strong Lensing Probabilities    p.10
    Jie Wang  
    Abstract | | PDF file (167 KB) | PS file *.gz  (142 KB) 
Extragalactic Astronomy
  • Color-Redshift Relations and Photometric Redshift Estimations of Quasars in Large Sky Surveys    p.17
    Xue-Bing Wu, Wei Zhang and Xu Zhou
    Abstract | | PDF file (381 KB) | PS file *.gz  (628 KB) 
  • An Intrinsic Model for the Polarization Position Angle Swing Observed in QSO 1150+812    p.37
    Shan-Jie Qian and Xi-Zhen Zhang 
    Abstract | | PDF file (220 KB) | PS file *.gz  (292 KB) 
  • Determination of the Thickness of Non-Edge-on Disk Galaxies    p.51
    Ying-He Zhao, Qiu-He Peng and Lan Wang 
    Abstract | | PDF file (180 KB) | PS file *.gz  (122 KB) 
  • The Difference between the $\alpha$-disks of Seyfert 1 Galaxies and Quasars    p.61
    Wei-Hao Bian, Hong Dong and Yong-Heng Zhao 
    Abstract | | PDF file (150 KB) | PS file *.gz  (95 KB)  
The Galaxy
Stars
  • A Photometry Campaign for IR Geminorum in Quiescence   p.88
    Hai Fu, Zong-Yun Li, Kam-Ching Leung, Zhou-Sheng Zhang, Zi-Li Li and C. Martin Gaskellg
     Abstract | | PDF file (426 KB) | PS file *.gz  (327 KB)  
The Solar System
  • Reflectance Spectral Characteristics of Lunar Surface Materials    p.97
    Yong-Liao Zou, Jian-Zhong Liu, Jian-Jun Liu and Tao Xu 
    Abstract | | PDF file (300 KB) | PS file *.gz  (124 KB) 

 


Abstract

 


Active Optics in LAMOST 

Ding-Qiang Su (1,2) and Xiang-Qun Cui (1)

Affiliation:  (1) National Astronomical Observatories/NIAOT, Chinese Academy of Sciences, Nanjing 210042
                  (2) Department of Astronomy, Nanjing University, Nanjing 210093
 
E-mail:   dqsu@nju.edu.cn 

Abstract

Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is one of the major national projects under construction in China. Active optics is one of the most important technologies for new large telescopes. It is used for correcting telescope errors generated by gravitational and thermal changes. Here, however, we use this technology to realize the configuration of LAMOST, --- a task that cannot be done in the traditional way. A comprehensive and intensive research on the active optics used in LAMOST is also reported, including an open-loop control method and an auxiliary closed-loop control method. Another important development is in our pre-calibration method of open-loop control, which is with some new features: simultaneous calculation of the forces and displacements of force actuators and displacement actuators; the profile of mirror can be arbitrary; the mirror surface shape is not expressed by a fitting polynomial, but is derived from the mirror surface shape formula which is highly accurate; a proof is given that the solution of the pre-calibration method is the same as the least squares solution.

Key words: galaxies: distances and redshifts --- techniques: active optics --- telescopes --- instrumentation: adaptive optics

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The Effect of Central Baryonic Cores in Dark Halos on the Evaluation of Strong Lensing Probabilities  

Jie Wang

 Affiliation:   National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012

E-mail:    wj@class2.bao.ac.cn 

Abstract

We present an estimate of the strong lensing probability by dark halos, with emphasis on the role of the baryonic matter arising purely from radiative cooling. We treat the contribution of the cooled baryons optimistically with all the cooled baryons confined within a central core, and including no feedback process from stellar evolution. Our two-component model provides a strong lensing probability that is in good agreement with the observed distribution of multiple images of quasars, provided that the cooled baryons are deposited within a spherical region of radius of 0.1 times the virial radius and follow an isothermal profile. It is pointed out that strong lensing may be used as an additional probe of baryon physics in dark halos though this may meanwhile complicate the test of the inner density profiles of dark matter in halos using the observed strong lensing probability.

Key words: cosmology: theory --- galaxies: halos --- gravitational lensing
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Color-Redshift Relations and Photometric Redshift Estimations of Quasars in Large Sky Surveys

Xue-Bing Wu (1), Wei Zhang (1) and Xu Zhou  (2)

Affiliation:   (1) Department of Astronomy, School of Physics, Peking University, Beijing 100871              
                    (2) National Astronomical Observatories, CAS (NAOC), Beijing 100012, China
              
E-mail:   wuxb@bac.pku.edu.cn   

Abstract

With a recently constructed composite quasar spectrum and the $\chi^2$ minimization technique, we describe a general method for estimating the photometric redshifts of a large sample of quasars by deriving theoretical color-redshift relations and comparing the theoretical colors with the observed ones. We estimated the photometric redshifts from the 5-band SDSS photometric data of 18678 quasars in the first major data release of SDSS and compared them with their spectroscopic redshifts. The difference is less than 0.1 for 47 % of the quasars and less than 0.2 for 68 %. Based on the calculation of the theoretical color-color diagrams of stars, galaxies and quasars both on the SDSS system and on the BATC system, we expect that we would be able to select candidates of high redshift quasars more efficaciously with the latter than with the former, provided the BATC survey can detect objects with magnitudes fainter than 21.

Key words: galaxies: photometry --- quasars: general --- quasars: emission lines -- surveys

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The Kiloparsec--scale Structure of 3C 286

Tao An, Xiao-Yu Hong and Wei-Hua Wang (1,2)

 Affiliation:  (1) Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030
                   (2) National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012      
E-mail:  antao@center.shao.ac.cn     

Abstract

We present radio images of the compact steep spectrum (CSS) quasar 3C 286 acquired with the Very Large Array (VLA) at 8.4 and 22.5 GHz. The source exhibits a two--sided core--jet structure with a bright central component and two extended components one to the east (P.A. 100°) and another to the southwest (P.A. -116°). From the compact core, an extension runs towards the southwest component up to $\sim$ 0.7 arcsecond. The emission between the primary central component and the southwest component exhibits a knotty structure. A gradual change of the jet position angles from -135° to -120° in the inner southwest jet suggests a local bend. The position angle changes of the major eastern components E2 and E1 suggest that the eastern jet likely follows a curved trace. The bends in the jet trace may be associated with a relativistic precession or some interaction between the jet and the ambient matter. A mean spectral index of $\alpha_{8.4}^{22.5}\sim -0.76$ ($S_{\nu}\propto\nu^{\alpha}$) is estimated for the core component. Steep spectra are also obtained for the extended southwest component (2.6'', P.A. -116°) and eastern component (0.8'', P.A. 100°), with $\alpha_{8.4}^{22.5}\sim-0.88$ and $\alpha_{8.4}^{22.5}\sim-1.79$, respectively. The radio morphologies and spectral index distributions suggest that the core seen in our images is likely to be the beamed inner jet while the real nucleus is dimmed by it beaming away from us.

Key words: galaxy: quasar: individual --- radio continuum: VLA

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An Intrinsic Model for the Polarization Position Angle Swing Observed in QSO 1150+812
Shan-Jie Qian and Xi-Zhen Zhang

Affiliation:   National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012

E-mail:   rqsj@bao.ac.cn    (coressponding author)
  
Abstract

The rapid polarization position angle swing of $\sim$ 180° observed in QSO 1150+812 at 2cm by Kochenov and Gabuzda is quite a regular event. One interesting property of the event is that, during the time of the swing the polarized flux density remained almost constant. We suggest that such an event can be explained in terms of a relativistic thin shock propagating through a uniform helical magnetic field, giving rise to relativistic aberration effects as the transverse field component rotates. The model may also be applicable to other similar events in which variations in polarization are not accompanied by variations in total flux density.

Key words: radio continuum: galaxies --- polarization --- quasars: individual: QSO 1150+812

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Determination of the Thickness of Non-Edge-on Disk Galaxies

Ying-He Zhao (1), Qiu-He Peng (1,2,3) and Lan Wang (1)
Affiliation:   (1) Department of Astronomy, Nanjing University, Nanjing 210093
                    (2) Joint Astrophysics Center of Chinese Academy of Science-Peking University, Beijing 100871
                    (3) The Open Laboratory of Cosmic Ray and High Energy Astrophysics, Chinese Academy of Sciences
                         
E-mail:    qhpeng@nju.edu.cn    (corresponding author)

Abstract

We propose a method to determine the thickness of non-edge-on disk galaxies from their observed structure of spiral arms, based on the solution of the truly three-dimensional Poisson's equation for a logarithmic disturbance of density and under the condition where the self-consistency of the density wave theory is no longer valid. From their measured number of arms, pitch angle and location of the innermost point of the spiral arms, we derive and present the thicknesses of 34 spiral galaxies.

Key words: galaxies: non-edge-on galaxies --- galaxies: spiral --- thickness: density wave theory

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The Difference between the $\alpha$-disks of Seyfert 1 Galaxies and Quasars

Wei-Hao Bian (1,2), Hong Dong (3) and Yong-Heng Zhao (1)

 Affiliation:    (1) National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012  
                    (2) Department of Physics, Nanjing Normal University, Nanjing 210097
                    (3) Department of Physics, Shangqiu Teachers College, Shangqiu 476000

E-mail:   whbian@lamost.bao.ac.cn   (corresponding author)

Abstract

In a previous paper, it was suggested that contamination of the nuclear luminosity by the host galaxy plays an important role in determining the parameters of the standard $\alpha$ disk of AGNs. Using the nuclear absolute B band magnitude instead of the total absolute B band magnitude, we have recalculated the central black hole masses, accretion rates and disk inclinations for 20 Seyfert 1 galaxies and 17 Palomar-Green (PG) quasars. It is found that a small value of $\alpha$ is needed for the Seyfer 1 galaxies than for the PG quasars. This difference in $\alpha$ possibly leads to the different properties of Seyfert 1 galaxies and quasars. Furthermore, we find most of the objects in this sample are not accreting at super-Eddington rates if we adopt the nuclear optical luminosity in our calculation.

Key words: galaxies: active --- galaxies: nuclei --- quasars: Seyfert

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A New Analysis in the Field of the Open Cluster Collinder 223

A. L. Tadross

Affiliation:   National Research Institute of Astronomy and Geophysics, 11421-Helwan, Cairo, Egypt
                    
E-mail:   altadross@mailer.scu.eun.eg (altadross@yahoo.com )

Abstract

The present study of the open cluster Collinder 223 (Cr 223) depended greatly on the photoelectric data of Clariá and Lapasset. We use the data in conjunction with the AAO/DSS1 image of the cluster in a re-investigation to improve the main parameters of Cr~223, including the stellar density, the position of the cluster's center, the cluster's diameter. Its luminosity function, mass function, and total mass are also estimated.

1  AAO: Anglo-Australian Observatory, DSS: Digitized Sky Surveys; taken from ``SIMBAD" ( http: //simbad.u-strasbg.fr ) 

Key words: Galaxy: open clusters and associations --- individual: Cr 223

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Radioactive Ages of Metal-Poor Halo Stars

Ji Li (1,2) and Gang Zhao (1)

 Affiliation:  (1) National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012
              (2) Department of Physics, Hebei Normal University, Shijiazhuang 050016
                    
E-mail:  jil@yac.bao.ac.cn     (corresponding author)

Abstract

The abundances of long-lived radioactive elements Th and U observed in metal-poor halo stars can be used as chronometers to determine the age of individual stars, and hence set a lower limit on the age of the Galaxy and hence of the universe. This radioactive dating requires the zero-decay productions of Th and U, which involves complicated r-process nucleosynthesis calculations. Several parametric r-process models have been used to calculate the initial abundance ratios of Th/Eu and U/Th, but, due to the sharp sensitivity of these models to nuclear physics inputs, the calculations have relatively large uncertainties which lead to large uncertainties in the age determinations. In order to reduce these uncertainties, we present a simple method to estimate the initial productions of Th and U, which only depends on the solar system abundances and the stellar abundances of stable r-process elements. From our calculations of the initial abundance ratios of Th/Eu and U/Th, we re-estimate the ages of those very metal-poor halo stars with published abundances of Th and U. Our age estimates are consistent, within the errors, with the other age determinations derived from r-process models, and offer useful constrains for r-process theoretical calculations. The advantages and limitations of our simple method of radioactive dating are discussed.

Key words: stars: abundances --- stars: Population II --- Galaxy: abundances --- Galaxy: halo --- Galaxy: evolution

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A Photometry Campaign for IR Geminorum in Quiescence

Hai Fu (1), Zong-Yun Li (1) ,Kam-Ching Leung (2), Zhou-Sheng Zhang (3), Zi-Li Li (3) and
C. Martin Gaskell (2)

 Affiliation:  (1) Department of Astronomy, Nanjing University, Nanjing 210093
                   (2) Department of Physics and Astronomy, University of Nebraska, Lincoln NE 68588-0111, USA
                   (3) National Astronomical Observatories, Yunnan Observatory,  Kunming  650011
                    
E-mail:   zyli@nju.edu.cn      (corresponding author)

Abstract

We report a  V band photometry of the SU UMa star IR Gem at quiescence in January 2002. The observations were made with two telescopes spaced $\sim$ 160° apart in longitude. Several photometric modulations have been found. One gives a period of 98.50(13) min, exactly equal to the orbital period determined spectroscopically. Two others occasionally strengthen and seem to be positive and negative superhumps with periods of 103.6(4) and 95.4(4) min, 5.2 % longer and 3.1 % shorter than the orbital period, respectively. A signal at $\sim$0.6 c/d in the power spectrum is roughly consistent with the expected period of nodal precession of the disk. There is a puzzling peak at 0.21(3) c/d corresponding to the $\sim$ 4.3 d sine wave seen in the raw light curve. We suspect it to be a beat frequency between the frequencies of apsidal and nodal precessions of the disk. Quasi-periodic cycles with amplitudes 0.15--0.6 mag can be seen in the light curve. The mechanism underlying this modulation is not clear.

Key words: accretion, accretion disks --- binaries: close --- novae, cataclysmic variables --- stars: dwarf nova --- stars: individual (IR Geminorum)

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Reflectance Spectral Characteristics of Lunar Surface Materials

Yong-Liao Zou (1), Jian-Zhong Liu (1), Jian-Jun Liu (1) and Tao Xu (2)

Affiliation:  (1) National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012
                   (2) Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002
                    
E-mail:  ylzou@bao.ac.cn    (corresponding author)

Abstract

Based on a comprehensive analysis of the mineral composition of major lunar rocks (highland anorthosite, lunar mare basalt and KREEP rock), we investigate the reflectance spectral characteristics of the lunar rock-forming minerals, including feldspar, pyroxene and olivine. The affecting factors, the variation of the intensity of solar radiation with wavelength and the reflectance spectra of the lunar rocks are studied. We also calculate the reflectivity of lunar mare basalt and highland anorthosite at 300, 415, 750, 900, 950 and 1000 nm. It is considered that the difference in composition between lunar mare basalt and highland anorthosite is so large that separate analyses are needed in the study of the reflectivity of lunar surface materials in the two regions covered by mare basalt and highland anorthosite, and especially in the region with high Th contents, which may be the KREEP-distributed region. 

Key words:  Moon --- mineral --- lunar rock

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ChJAA, 2004, Vol.4, No.1

Chinese Journal of Astronomy and Astrophysics: Online Edition

http://www.chjaa.org 

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