ChJAA -- 2003, Vol.3, No.5

2003, Vol.3, No.5 (October 20, 2003)

Contents

Letter

Wavelet Analysis of Several Important Periodic Properties in the Relative Sunspot Numbers p.391
Gui-Ming Le and Jia-Long Wang
Abstract | | PDF file (693 KB) | PS file *.gz (645 KB)

Cosmology

Time Scales and Tidal Effects in Minor Mergers p.395
Yu Lu and Jian-Yan Wei
Abstract | | PDF file (531 KB) | PS file *.gz (1311 KB)

Relativistic Corrections to the Thermal Sunyaev-Zel'dovich Power Spectrum p.410
Hai-Ning Li
Abstract | | PDF file (141 KB) | PS file *.gz (89 KB)

Extragalactic Astronomy

Spectral Indices of Core and Extended Components of Extragalactic Radio Sources p.415
Jiang-Shui Zhang and Jun-Hui Fan
Abstract | | PDF file (160 KB) | PS file *.gz (148 KB)

Discovery of Five Narrow-Line Seyfert 1 Galaxies and Implications on the NLS1 Model p.423
Jiang-Hua Wu, Xiang-Tao He, Yang Chen and Wolfgang Voges
Abstract | | PDF file (614 KB) | PS file *.gz (673 KB)

The Galaxy

Galactic Chemical Evolution of the Lighter Neutron Capture Elements Sr, Y and Zr p.431
Cui-Hua Du, Bo Zhang, Han-Feng Song and Qiu-He Peng
Abstract | | PDF file (267 KB) | PS file *.gz (364 KB)

Stars

Can the Inner Gap Sparking Take Place in Millisecond Pulsars? p.443
Hong-Guang Wang, Guo-Jun Qiao and Ren-Xin Xu
Abstract | | PDF file (266 KB) | PS file *.gz (435 KB)

Lithium Abundance of Metal-poor Stars? p.453
Hua-Wei Zhang and Gang Zhao
Abstract | | PDF file (130 KB) | PS file *.gz (107 KB)

Large-Scale Distribution of Herbig-Haro Objects in Taurus? p.458
Ke-Feng Sun, Ji Yang, Shao-Guang Luo, Min Wang, Li-Cai Deng, Xu Zhou and Jian-Sheng Chen
Abstract | | PDF file (1694 KB) | PS file *.gz (1535 KB)

An Analysis of Average Pulsar Profiles and A Study of the $\rho\,-P$ relation of Pulsars? p.469
Hua-Xiang Wang and Xin-Ji Wu
Abstract | | PDF file (219 KB) | PS file *.gz (252 KB)

Instruments, observational techniques and data processing

A Study of the Fitting Accuracy of the Active Reflector for a Large Spherical Radio Telescope p.478
Xiao-Qiang Tang, Jin-Song Wang and Qi-Ming Wang
Abstract | | PDF file (325 KB) | PS file *.gz (963 KB)

Abstract

Wavelet Analysis of Several Important Periodic Properties in the Relative Sunspot Numbers

Gui-Ming Le (1) and Jia-Long Wang (2)

Affiliation:  (1) Center for Space Science and Applied Research, Chinese academy of Sciences, Beijing 100080
               (2) National Astronomical Observatories, CAS (NAOC), Beijing 100012, China

E-mail:   lgm@earth.sepc.ac.cn

Abstract

We investigate the wavelet transform of yearly mean relative sunspot number series from 1700 to 2002. The curve of the global wavelet power spectrum peaks at 11-yr, 53-yr and 101-yr periods. The evolution of the amplitudes of the three periods is studied. The results show that around 1750 and 1800, the amplitude of the 53-yr period was much higher than that of the the 11-yr period, that the ca. 53-yr period was apparent only for the interval from 1725 to 1850, and was very low after 1850, that around 1750, 1800 and 1900, the amplitude of the 101-yr period was higher than that of the 11-yr period and that, from 1940 to 2000, the 11-yr period greatly dominates over the other two periods.

Key words: Sun: sunspots --- Sun: activity --- methods: data analysis

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Time Scales and Tidal Effects in Minor Mergers

Yu Lu and Jian-Yan Wei

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

E-mail:   luyu@nova.astro.umass.edu    (corresponding author)

Abstract

We use controlled N-body simulation to investigate the dynamical processes (dynamical friction, tidal truncation, etc.) involved in the merging of small satellites into bigger halos. We confirm the validity of some analytic formulae proposed earlier based on simple arguments. For rigid satellites represented by softened point masses, the merging time scale depends on both the orbital shape and concentration of the satellite. The dependence on orbital ellipticity is roughly a power law, as suggested by Lacey & Cole, and the dependence on satellite concentration is similar to that proposed by White. When merging satellites are represented by non-rigid objects, Tidal effects must be considered. We found that material beyond the tidal radius are stripped off. The decrease in the satellite mass might mean an increase in the merging time scale, but in fact, the merging time is decreased, because the stripped-off material carries away a proportionately larger amount of of orbital energy and angular momentum.

Key words: cosmology: dark matter --- galaxies: kinematics and dynamics --- galaxies: structure --- galaxies: interactions --- numerical methods

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Relativistic Corrections to the Thermal Sunyaev-Zel'dovich Power Spectrum

Hai-Ning Li (1,2)

Affiliation:   (1) National Astronomical Observatories, CAS (NAOC), Beijing 100012, China
              (2) Department of Astronomy, Beijing Normal University, Beijing 100875

E-mail:   lhn@class2.bao.ac.cn

Abstract

We present a quantitative estimate of the relativistic corrections to the thermal SZ power spectrum produced by the energetic electrons in massive clusters. The corrections are well within 10% for current experiments with working frequencies below $\nu<100$ GHz, but become non-negligible at high frequencies $\nu >350$ GHz. Moreover, the corrections appear to be slightly smaller at higher $\ell$ or smaller angular scales. We conclude that there is no need to include the relativistic corrections in the theoretical study of the SZ power spectrum especially at low frequencies unless the SZ power spectrum is used for precision cosmology.

Key words: cosmic microwave background --- cosmology: theory --- galaxies: clusters: general

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Spectral Indices of Core and Extended Components of Extragalactic Radio Sources

Jiang-Shui Zhang and Jun-Hui Fan

Affiliation: Center for Astrophysics, Guangzhou University, Guangzhou 510400

E-mail: zjshui@163.net

Abstract

We use observed peak and total flux densities at 6cm and 20cm to determine the spectral indices separately for the core and extended components of QSOs and galaxies, as well as their core-dominance parameters. Our results indicate that 1) Nine QSOs show both greater than 1.0 core-dominance parameters (those objects should be blazars) and greater than 0.5 spectral indices. The average core spectral index is $\alpha_{\rm Core}$ = 0.85 $\pm$ 0.21 for the nine blazars, which implies that it is not reliable to use $\alpha_{\rm radio}=0.0$ for blazars. For the different subclasses, the core and extended spectral indices are as follows: for the blazars, $\alpha_{\rm Core}$ = 0.22 $\pm$ 0.06 and $\alpha_{\rm Ext}$ =0.77 $\pm$ 0.12; the galaxies, $\alpha_{\rm Core}$ = 1.01 $\pm$ 0.13 and $\alpha_{\rm Ext}$ =0.83 $\pm$ 0.21, and for the QSOs, $\alpha_{\rm Core}$ = 0.28 $\pm$ 0.10 and $\alpha_{\rm Ext}$ =0.68 $\pm$ 0.08. 2) The core spectral index and core dominance parameter (R) show an anti-correlation, $\alpha_{\rm C} = (-1.28\pm0.26) \log R +(0.65\pm0.11)$ ; 3) R is approximately linearly correlated with redshift (z).

Key words: galaxies: active --- radio continuum: galaxies

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Discovery of Five Narrow-Line Seyfert 1 Galaxies and Implications on the NLS1 Model

Jiang-Hua Wu (1), Xiang-Tao He (2), Yang Chen (2) and Wolfgang Voges (3)

Affiliation:   (1) National Astronomical Observatories, CAS (NAOC), Beijing 100012, China
              (2) Department of Astronomy, Beijing Normal University, Beijing 100875
       (3) Max-Planck-Institut f\"ur Extraterrestrische Physik, D-85740 Garching, Germany

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

Abstract

We report the discovery of five Narrow-Line Seyfert 1 galaxies (NLS1s) identified from the ROSAT All-Sky Survey bright sources. One of them has a quasar-like luminosity and two, including the quasar-like one, have close companions and/or show interacting features. We calculate the central black hole masses and Eddington ratios for the five NLS1s. In combination with the objects of Kaspi et al., we find that NLS1s have smaller central black hole masses and higher accretion rate than normal Seyfert 1s.

Key words: black hole physics --- galaxy: active --- galaxy: Seyfert --- X-ray: galaxy

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Galactic Chemical Evolution of the Lighter Neutron Capture Elements Sr, Y and Zr

Cui-Hua Du (1,2), Bo Zhang (1,3), Han-Feng Song (1) and Qiu-He Peng (4)

Affiliation:   (1) Department of Physics, Hebei Normal University, Shijiazhuang 050016
              (2) National Astronomical Observatory, Chinese Academy of Science, Beijing 100012
            (3) Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 730000
              (4) Department of Astronomy, Nanjing University, Nanjing 210093

E-mail:    dch@vega.bac.pku.edu.cn; zhangbo@hebtu.edu.cn (corresponding authors)

Abstract

Based on a three-component Galaxy chemical evolutionary model satisfying a large set of Galactic and extragalactic constraints, we compute the chemical evolution of the lighter neutron capture elements (e.g., Sr, Y and Zr) taking into account contributions from three processes. We compare our model results with available observational results and find that the observed trends can be understood in the light of present knowledge of neutron capture nucleosynthesis.

Key words: stars: AGB and post-AGB --- Galaxy: halos --- ISM:abundances

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Can the inner gap sparking take place in millisecond pulsars?

Hong-Guang Wang, Guo-Jun Qiao and Ren-Xin Xu

Affiliation:    Department of Astronomy, Peking University, Beijing 100871

E-mail:   cosmic008@263.net (corresponding author)

Abstract

The inner vacuum gap model has become the foundation stone of most theories on pulsar radio emission. The fundamental picture of this model is the sparking, which was conjectured to be induced by magnetic absorption of background gamma photons. However, a question is, can the sparking be triggered in the millisecond pulsars (MSPs) with magnetic fields (B) only about 10⁸ G? We investigate this problem by including the pair production above the inner gap. Under the assumption that the magnetic field is dipolar, our results show the background gamma-ray emission can not be the key factor that triggers the sparking, at least not in MSPs with $B\sim10^8$ G, if the temperature in the polar cap region is only so high as is observed (<4×10⁶K). Some other mechanisms are required.

Key words: pulsar: general---gamma rays---magnetic fields

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Lithium Abundance of Metal-poor Stars

Hua-Wei Zhang (1,2,3) and Gang Zhao (1)

Affiliation: (1) National Astronomical Observatories, CAS (NAOC), Beijing 100012, China
              (2) Department of Astronomy, School of Physics, Peking University, Beijing 100871
       (3) Chinese Academy of Sciences-Peking University Joint Beijing Astrophysical Center, Beijing 100871

E-mail:   zhw@bac.pku.edu.cn (corresponding author)

Abstract

High-resolution, high signal-to-noise ratio spectra have been obtained for 32 metal-poor stars. The equivalent widths of Li $\lambda$ 6708 Å were measured and the lithium abundances were derived. The average lithium abundance of 21 stars on the lithium plateau is 2.33 $\pm$ 0.02 dex. The Lithium plateau exhibits a marginal trend along metallicity, dA(Li)/d[Fe/H] = 0.12 $\pm$ 0.06, and no clear trend with the effective temperature. The trend indicates that the abundance of lithium plateau may not be primordial and that a part of the lithium was produced in Galactic Chemical Evolution (GCE).

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

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Large-Scale Distribution of Herbig-Haro Objects in~Taurus

Ke-Feng Sun (1,2,3), Ji Yang (3,4), Shao-Guang Luo (1,2), Min Wang (3,4), Li-Cai Deng (2,4), Xu Zhou (2,4) and Jian-Sheng Chen (2,4)

Affiliation: (1) Department of Astronomy, Peking University, Beijing 100871
              (2) Chinese Academy of Sciences-Peking University Joint Beijing Astrophysical Center, Beijing 100871
       (3) Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008
       (4) National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012

E-mail:   sunkf@water.pku.edu.cn   (corresponding author)

Abstract

We report our new results on Herbig-Haro (HH) objects in the star forming region of Taurus from a wide-field survey with the 60/90 cm Schmidt telescope of the Beijing Astronomical Observatory. This survey using CCD imaging with a narrow band [SII] filter and an intermediate band [BATC10] filter covered approximately 30 square degrees in Taurus. Besides confirming the known HH Objects in the region, we discovered seven new HH candidates, and groups. Six of these are HH 701A-B, HH 702A-D, HH 703, HH 704A-D, HH 705, HH 706 and the seventh is a group, a new component of HH 319, labeled HH 319B-D. Based on the large-scale distribution of pre-main-sequence (PMS) stars in Taurus, we analyze statistically the most probable distance from the HH objects to each PMS star, from which we estimate the typical timescale of these HH objects to be between (1.3

2.0)×10⁴ yrs; and we also obtain the birth rates of HH objects: 0.447 $\pm$ 0.198 for Class I PMS stars, 0.360 $\pm$ 0.222 for Class II PMS stars, and

0.148 $\pm$ 0.234 for Class III PMS stars.

Key words: ISM: Herbig-Haro objects --- ISM: individual (Taurus region) --- ISM: jets and outflows --- star: formation --- stars: pre-main-sequence

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An Analysis of Average Pulsar Profiles and A Study of the $\rho\,-P$ relation of Pulsars

Hua-Xiang Wang and Xin-Ji Wu (1,2,3)

Affiliation: (1) Department of Astronomy, Peking University, Beijing 100871
              (2) Urumqi Astronomical Station, National Astronomical Observation, Urumqi 830011
       (3) CAS-PKU Joint Beijing Astrophysics Center, Beijing 100871

E-mail:   wuxj@vega.bac.pku.edu.cn (corresponding author)

Abstract

Using the method of Gaussian Fit Separation of Average Profile (GFSAP), we re-examine the average profiles of nine pulsars at several frequencies, ranging from 408--1642 MHz. This method enables us to obtain the number of components for each pulsar, and the parameters for each component, the width, position and amplitude. The $\rho\,-P$ relation for the inner cone and outer cone are studied separately, and the results are, respectively, $\rho = P^{-0.51 \pm 0.05 }$ and $\rho = P^{-0.42 \pm 0.06}$ . The results can be interpreted as a confirmation of the double-cone structure of pulsar emission beams. The altitudes of emission region, and the radius-to-frequency-map (RFM) are also examined; for the outer cone, we obtained $r(\nu)\propto \nu^{-0.19 \pm 0.09}$ .

Key words: stars: pulsar: general --- line: profiles

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A Study of the Fitting Accuracy of the Active Reflector for a Large Spherical Radio Telescope

Xiao-Qiang Tang (1), Jin-Song Wang (1) and Qi-Ming Wang (2)

Affiliation: (1) Department of Precision Instruments, Tsinghua University, Beijing, 100084
              (2) National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012

E-mail:   tangxq@pim.tsinghuia.edu.cn   (corresponding author)

Abstract

We propose a spatial three-degree-of-freedom (DOF) parallel mechanism combining two degrees of rotations and one degree of translation to support the active reflector units of a large spherical radio telescope. The kinematics, workspace and accuracy of the mechanism are analyzed. One-dimensional and two-dimensional fitting errors to the working region of active reflector are investigated. Dimensional parameters of the mechanism and active reflector unit are examined with respect to the requirement of fitting accuracy. The result of accuracy analysis shows the effectiveness and feasibility of the proposed mechanism, and gives a design rule to guarantee the highest working frequency required by large radio telescope.

Key words: telescopes: radio telescope --- active reflector

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