Richard Wielebinski
p022rwi@mpifr-bonn.mpg.de
Max-Planck-Institut
für Radioastronomie, Bonn
The recent years have
seen the 'closing' of the window between radio astronomy and far infrared
observations. Several telescopes exist capable of sub-mm wavelength observations,
more are under construction. Radio astronomy at cm wavelengths studies
thermal (free-free) emissions from hot gas and non-thermal radiation from
magnetic fields and relativistic electrons. When we move into the mm wavelengths
range we can study many molecular lines as well as emission from cold dust.
At sub-mm wavelengths the lines become a forest and the continuum emission
comes from warm dust. In recent years we have made studies of nearby galaxies
with the Pico Veleta 30m telescope in the CO(1-0) and CO(2-1) line, as
well as in ? = 1.2 mm radio continuum. Some of the studied objects were
re-observed with better angular resolution with the Plateau de Bure mm-wave
interferometer. The HHT telescope on Mt.Graham was used to make observation
in the CO(3-2) and CO(4-3) lines as well as in ? = 870µ radio continuum.
The combination of all these data allow us to study warm CO gas and cold
dust in these galaxies. A surprising result was the discovery of widely
distributed warm gas in galaxies. I will in addition describe the project
APEX, a 12m pathfinder radio telescope for sub-mm wavelengths to be constructed
on the Chajantor site in Chile at the elevation of 5080m. I will also mention
briefly the present status of the ALMA projece
Studies of massive star formation with centimeter-millimeter emission
Yuefang Wu
ywu@vega.bac.pku.edu.cn
Astromony department,
Peking University
Millimeter-centimeter
lines brought us many remarkable discoveries in the regions of massive
star formation. Centimeter continuum emission also make it possible for
a signpost of massive star forming-UC HII regions tobe clearly established.
Owing to the relative distance and complex birth places of massive stars
and their rapid evolution, the characteristics of the earliest stage of
massive star formation are too difficult to catch. Studies on massive star
formation are lagging behind compared to the studies on low-mass star formation.
Now because of the advancement of technology the difficult problems for
deeply probing the earliest phase of massive stars are being solved. Phenomena
of evolution phases earlier than UC HII regions are observed. Studies for
massive star formation are in bloom.
M E G A M A S E R S
Christian Henkel
chenkel@mpifr-bonn.mpg.de
MPIfR, Bonn
To date five molecular
species are known to show maser emission in external galaxies: H2O,
OH, H2CO, CH, and SiO. While SiO and CH masers appear to be
similar to those observed in the Galaxy, but often more luminous, H2CO,
OH, and H2O masers can be principally different. Of particular
interest are the water vapor masers that provide the only emission lines
from accretion disks that can be directly imaged in active galactic nuclei.
The properties of this emission, emphasizing the derivation of phyical
parameters including temperature, magnetic field, disk stability, mass
accretion rate, heating of the disk, disk orientation, spin direction and
degree of warping, will be discussed. Emphasized are also H2O
masers associated with nuclear jets. The physics of OH mega-and gigamasers,
their association with ultraluminous galaxies, and their high potential
relevance for cosmological studies will be another topic of this talk.
A study of megamaser galaxies
Zhiyao Yu
zyyu@center.shao.ac.cn
Shanghai Astronomy Observatory
This paper has studied
the infrared property of OH megamaser galaxies, and its relationship with
the observational character of OH megamaser.
Multiple line study of HH106
Junzhi Wang
Astronomy Department,
Peking University
Not available yet!
Feasibility study on the FAST
Rendong Nan
nrd@bao.ac.cn
NAOC
A Five hundred meter
Aperture Spherical Telescope, FAST, is proposed to be built in the karst
region of southwest China. This project is also an effort for the international
cooperation in the Kilometer Square Array - SKA. The feasibility study
on the FAST concept with theoretical analysis and model experiments were
funded in 1999, and its results has been evaluated to be successful at
the end of 2001 by the CAS. Study phase of the FAST approved the feasibility
of the layout of the telescope on the whole. Many questions, however, were
also brought forward from those model tests - reliability, maintenance
and the construction cost. An improved down scale models of the cable feed
supporting and cable-net active reflector are under construction and experiment.
The 100-m Effelsberg Telescope and the Milky Way
Ernst Fuerst
efuerst@mpifr-bonn.mpg.de
MPIfR, Bonn
The Effelsberg 100-m
radio telescope began it's astronomical operation in 1971. For about 30
years it was the largest fully steerable radio telescope. Observations
can be done from the prime focus as well as from the secondary, gregorian,
focus. The large focal length of the secondary focus allows the installation
of a large number of receivers and multi-feed systems. Some technical details
of the telescope are described, which are relevant for the quality of the
observations. Since the beginning, the 100-m radio telescope contributes
to all fields of radio astronomy: radio continuum, spectroscopy, pulsar
research and VLBI. The telescope is well suited to map large areas of the
sky in the radio continuum, in total intensity and polarization. As an
example, the plane of the Milky Way at radio waves is presented. Such data
in combination with follow-up measurements at other radio frequencies provide
spectral and polarization information on various objects of the Milky Way.
A few examples are discussed. At the 100-m telescope, observations at wavelengths
shorter than 1~cm will become more and more important. Large arrays will
help to speed up mapping of extended areas. A proposal exists to improve
the sensitivity of the 100-m radio telescope especially at short wavelengths.
A comment on this project is given.
VLBI facilities and observations in China
X. Y. Hong1,
J. Zhang2, X. Z. Zhang1
xhong@center.shao.ac.cn
Current Projects and New Initiatives on Radio Telescope
Dehua Yang
dhyang@nairc.ac.cn
NIAOT, NAOC
With the development
of radio astronomy, observation is covering the whole band of electromagnetic
radiation and even the cosmic rays, especially the section of wavelength
between submillimeter and millimeter. Thus, more powerful observing facilities
are needed. This paper reviews current projects and new initiatives on
radio telescope mainly working at submillimeter and millimeter bands, and
describes key technology and special consideration involved on design of
such telescopes . The paper also briefs radio telescope programs running
in China.
An introduction to the new Miyun 50m radio telescope
Chengjin Jin
cjjin@bao.ac.cn
NAOC
An introduction to
the new Miyun 50m radio telescope will be given, including the main scientific
driver and the specifications of the telescope. The overall layout design
and the working schedule will also be introduced.
A Study of Optimization of the Focus in the FAST
Shengyin Wu
wsy@bao.ac.cn
NAOC
It is important to
choose an optimal focus in the project FAST to ensure a minimum r.m.s.
displacement from a spherical surface to a parabolic reflector, a minimum
deviation of spherical (or planar) panel elements from the parabola simulated,
a minimum relative displacement of panel elements for simulating a parabolic
reflector from the neutral spherical surface and a feasibility of utilization
of multi-parabola fitting scheme. An optimal focus could also reduce problems
due to differences of radial arc length and reflector area between parabolic
reflector simulated and corresponding spherical surface as far as possible
and errors in programming and adjusting the panels. A choice of the focus
would influence the design and installation of any multi-beam feed on the
FAST. A study of optimization of focus in the FAST is introduced in this
report.
An optimal UV coverage design of KARST for SKA
Yan Su
suyan@bao.ac.cn
NAOC
China is contributing
to the FAST project, as a pilot of international project SKA. The Chinese
SKA, KARST, consists of about 30 individual FAST type elements, each roughly
200 m in diameter. More than 300 hundred candidate karst depressions in
south of Guizhou Province in China have been detected. How to arrange the
30 elements array, and get the best UV coverage is one important problem.
We consider one possible optimized way to sort it out here.
Sub-mm Dust Emission in Massive Star Forming Regions
Ruiqing Mao
rqmao@jets.pmo.ac.cn
PMO, Nanjing
We present 870 micron
images of about 80 massive star forming regions taken at 22" resolution
with a newly installed 19 pixels bolometer on the HHT-10m. Strong sub-mm
dust emission is detected for almost all sources associated with 6.7GHz
methanol masers with only two exceptions toward which there was no dust
emission under a noise level of 0.2 Jy. Some interesting sources were also
mapped in the CO(3-2) and outflow activities are found to be quite common
in massive star forming regions. The relationships among massive YSOs,
molecular outflows and methanol masers are also discussed.
Spectral system of Urumqi telescope and water maser study
Jarken.E, Y.Wu
jarken@vega.bac.pku.edu.cn
Astronomy Department, Peking
University
Introduction of Spectral
system of Urumqi telescope. We collected noth and sourth hemisphere water
masers and analyzed global properties of all water masers associated with
IRAS-MSX sources, discussed relation berween water masers with pumping
mechanism.
The Mapping Study of High-velocity Gas near Young Stellar Objects
Yang Wang , Yuefang
Wu
pkuywang@sina.com
Astronomy Department,
Peking University
It is now generally
believed that during the earliest stages of evolution, stars undergo a
phase of very energetic mass ejection ,frequently characterized by the
occurrence of massive bipolar outflows of molecular gas. The broad molecular
emission line is an evidence of high-velocity molecular gas, but it also
the evidence of turbulence and rotation. So mapping the region of high-velocity
is an effective method to identify the outflows around young stellar. The
Outflow Statistical Catalog (Wu et al. in 1996) still have some object
that did not map to identify the outflows composition. Observation were
made with the 13.7m telescope at Qinhai Station for ten sources. The result
and a discussion are present in this paper.
A bipolar molecular outflow near IRAS 02461+6147
Yun Shi
Astronomy Department,
Peking University
Not available yet!
CO and its isolate study for IRAS 00117+6412
Ming Zhao
Astronomy Department,
Peking University
Not available yet!
Mapping studies of high velocity gas sources
Wentao Yu
Astronomy Department,
Peking University
Not available yet!
A study of molecular outflows
K. Sun, Y. Wu
Astronomy Department,
Peking University
Not available yet!
A mapping study for S106
Y. Wei, Y. Wu
Astronomy Department,
Peking University
Not available yet!
Observations of Galactic magnetic fields
Wolfgang Reich
p098wre@mpifr-bonn.mpg.de
MPIfR, Bonn
Radioastronomical methods
are used to reveal the properties of Galactic magnetic fields. Their strength
and regularity are derived from multi-wavelengths observations of synchrotron
emission and its percentage polarization. Faraday effects cause depolarization
and enhance the rotation measure of extragalactic sources, pulsars and
supernova remnants. Rotation measures carry information on the magnetic
field strength along the line of sight coupled to the warm interstellar
medium. Recently, substantial progress has been made in Galactic polarimetry
tracing magnetic fields on scales ranging from sub-pc to several hundred
pc. That is essential to understand the average field properties on kpc
scales, which is at present easier to observe and hence better known for
nearby normal galaxies. New results from polarization observations made
with the Effelsberg 100-m telescope are discussed. Multi-frequency data
show a highly structured magneto-ionic interstellar medium. High frequency
observations reveal the unusual properties of the poloidal magnetic field
in the Galactic Centre region. Polarized Galactic high latitude emission
acts as a 'foreground' for observations of the cosmic microwave background
and needs to be better known at high frequencies.
Large scale surveys of the Galaxy
Patrica Reich
preich@mpifr-bonn.mpg.de
MPIfR, Bonn
The radio luminosity
of normal galaxies is not very high and requires the largest telescopes
to observe them. Principally the best case to study normal galaxies is
our own one, however, our unfavourable location within the Galaxy makes
it necessary to observe large-scale surveys at different frequencies in
order to derive physical properties of the Galaxy. For a long time the
408 MHz all-sky-survey and the 1420 MHz survey of the northern sky have
been the most reliable surveys to perform these studies. In the last years
the 1420 MHz survey has been extended to an all-sky survey and also at
22, 45 and 2625 MHz large portions of the Galaxy have been published. Now
there is an unprecedented database for Galactic studies available. One
key information derived from those data is the distribution of spectral
indices. For their computation the absolute calibration of those surveys
is the most important requirement. The absolute zero levels and the impact
of other insufficiencies of the surveys on the spectral index maps will
be discussed. Some preliminary results will be presented.
The global structure of magnetic fields in our Galaxy
JinLin Han
hjl@bao.ac.cn
NAOC
Not available yet!
The 'tomography' of the magnetic interstellar medium
Richard Wielebinski
p022rwi@mpifr-bonn.mpg.de
Max-Planck-Institut
für Radioastronomie, Bonn
The Galaxy is a conglomerate
of many components. We observe starlight, radio continuum, HI radio line,
various molecular lines, UV and IR radiation, X-ray emissions and even
?-ray events. Recent observations have shown that all this interstellar
medium is permeated by magnetic fields. We know little about the origin
of magnetic fields. We have just started to trace the distribution of magnetic
fields in our Galaxy, nearby galaxies, radio galaxies and clusters of galaxies.
At this stage we can say that every object seems to possess a magnetic
field. However we still cannot decide if the magnetic fields are just a
consequence of rotation only or if they play an active role in the dynamics
of galaxies. I will present some recent observations on our Milky Way and
for nearby galaxies. In particular I will show how different types of observations
can be combined, especially for our Galaxy, to reconstitute the distribution
of the magnetic fields in three dimensions: hence perform a 'tomography'
of the magnetic interstellar medium.
Velocity stratification, azimuthal magnetic field and the RM sky
Hui Men
mh@bao.ac.cn
NAOC
Not available yet!
Radio observations of the magnetic fields in galaxies
Marita Krause
mkrause@mpifr-bonn.mpg.de
MPIfR, Bonn
Radio observations
of the continuum emission turned out to be the most powerful tool to study
the magnetic fields in galaxies. The total intensity of the synchrotron
emission gives the strength of the total magnetic field. The linearly polarized
intensity reveales the strength and structure of the resolved regular field
in the plane of the sky whereas a map of the Faraday rotation measure gives
the strength and direction of the field components along the line of sight.
Combining both data sets enables us to perform a 'tomography' of the magnetic
field. The magnetic field in flat galaxies turned out to be mainly parallel
to the disk. Well-ordered magnetic fields with a large-scale spiral structure
are found in grand design, flocculent and even irregular galaxies. In grand-design
galaxies the magnetic fields are aligned parallel to the optical spiral
arms. The strongest regular fields are found in the interarm regions, sometimes
forming 'magnetic spiral arms' between the optical arms. Faraday rotation
of the polarization vectors reveals coherent large-scale fields as expected
by the generation of a large-scale dynamo. A few galaxies show a dominating
axisymmetric spiral pattern. However, the majority of field structures
in galaxies seem to be a superposition of different dynamo modes. Recent
studies of magnetic fields in barred galaxies and spiral galaxies seen
edge-on will also be discussed.
Gaseous halos and the disk-halo interaction in spiral galaxies
Ralf-Juergen Dettmar
dettmar@astro.ruhr-uni-bochum.de
Astronomical Institute,
Ruhr-University Bochum, D-44780 Bochum, Germany
Ever since the first
evidence for radio-continuum halos in the Milky Way and other galaxies
- such as in the prototypical case of NGC 4631 - the physical processes
for the origin of gaseous galactic halos were mainly sought in the feedback
of energy into the interstellar medium (ISM) by young stars through winds,
the interstellar radiation field, and (multiple) supernova explosions.
>From this general idea the concept of the disk - halo interaction emerged
in which the disk medium can connect to the halo. This is described in
different model approaches in term of galactic fountains, chimneys, or
super - bubble - outbreak by theory. Observational support for the idea
of such a large scale matter exchange between disk and halo comes from
observations of gaseous halos in external galaxies (e.g., Dahlem 1997,
Dettmar 1998). While several phases of the ISM - from cold HI to X-ray
coronae - have meanwhile been found in the halos of spiral galaxies. the
H+ represents a particularly important constituent, since it
is relatively easily observed in the optical (Dettmar 1992, 1998). Therefore,
imaging in and spectroscopy of optical emission lines allow us to study
the distribution and excitation of this Diffuse Ionized Gas (DIG, or WIM
for Warm Ionized Medium) with a spatial resolution not achievable for other
phases of the ISM in external galaxies. In order to demonstrate this point
we will present results from a new quantitative survey for H+
halos of edge-on galaxies (Rossa & Dettmar 2002). The data confirm
that the presence of DIG in the disk-halo interface of spiral galaxies
is related to star formation processes in the underlying disk and allow
us to establish a minimum energy release per unit area that is required
to start the disk-halo mass exchange. Comparing some recent observational
results for diagnostic emission lines with model predictions from photoionization
and shock models (Tullmann & Dettmar 2000) we demonstrate that the
origin and excitation of the DIG is, however, still not completely understood
and that a discussion gives indeed important constraints for models of
the ISM in general and on the disk-halo connection in particular. In comparison
with similar for the Milky Way the need for an additional heating source
is established. Special emphasis will be given to some recent developments.
We will discuss now kinematical information for the DIG layer in NGC 5775
from ESO/VLT long-slit spectra in connection with the magnetic field structures
in the halo of this object as deduced from VLA radio-continuum jpolarization
data (Tullmann et al. 2001). Finally, the role of dust for the physical
process in the disk-halo interface will be addressed.
Cosmic Plasma Dynamo
Zhiliang Yang
zlyang@bnu.edu.cn
Department of Astronomy,
Beijing Normal University
The plasma is described
by magnetic field or current. The general MHD is in the way describing
plasma with magnetic field. However, it is not suitable for the magnetic
generation (Alfven, 1981, Cosmic Plasma). To describe the dynamo effect,
MHD is not a right way. The particle property should be considered in dynamo
effect. Eventually with a infinite field description for a finite object
by the MHD is erroneous. The polarization of plasma is important for a
finite object consisting of plasma. The dynamic equation for moving plasma
with its polarization considered is presented in this paper. It may be
an extended MHD equation. In low frequent electromagnetic field, polarization
is important. From the extended MHD equations considering the polarization,
we get the dynamo effect in plasma.
Modelling the evolving cosmological magnetic fields
Xiaopeng You
xpyou@bao.ac.cn
NAOC
Not available yet!
Magnetic fields in galaxies: their origin and their impact on the ISM
Katia Ferriere
ferriere@ast.obs-mip.fr
Obs-mip, France
In the first part of
the
talk, I will discuss the origin of galactic magnetic fields. After showing
that the primordial field theory is in disagreement with observations,
I will present the dynamo theory in which large-scale magnetic fields are
amplified under the combined action of the large-scale galactic differential
rotation and small-scale cyclonic turbulent motions. I will describe the
threefold role played by turbulent motions in the dynamo process: generation
of magnetic field in the direction perpendicular to the prevailing field
(alpha effect), vertical transport of magnetic field lines, and turbulent
magnetic diffusion. I will then present numerical solutions of the galactic
dynamo equation for a supernova-driven turbulence. In the second part of
the talk, I willdiscuss the impact of galactic magnetic fields on the interstellar
medium. Through the Lorentz force, they affect both the dynamics and the
spatial distribution of the ordinary matter at all scales. At large scales,
they help to support it against its own weight, while they confine cosmic
rays to the galaxy. At smaller scales, they oppose the expanding gas motions
driven by supernova explosions, they constrain the random motions of interstellar
clouds, and they control the star formation process. In addition to their
dynamical role, they provide a heat source for the interstellar gas through
magnetic reconnection.
Discovery of Double Quasi-Periodic Oscillations in Sgr A*
Jun-Hui Zhao
jzhao@cfa.harvard.edu
CfA, Harvard
We report the discovery
of double quasi-periodic oscillations in the radio flux density of Sgr
A* based on the densely sampled radio light curves observed with the VLA
in the past two years. The new VLA data shows both the quasi-periodic oscillations
at periods of 132 and 330 days. The ratio of the two periods appears to
be 2.5, which is a suggestive of a resonance of orbital motions occurring
in the accretion disk around the supermassive black hole at the Galactic
center.
Magnetic fields in late-type stars
Jianrong Shi
sjr@yac.bao.ac.cn
NAOC
Not available yet!
Solar Radio Spectrometer Observations of Burst Events During 23rd Solar Maximum
Yihua Yan
yyh@bao.ac.cn
NAOC
Not available yet!
Pulsars: Some Observational Constraints on Theoretical Models
A.. Jessner
ajessner@MPIfR-Bonn.MPG.de
MPIfR Radio observatory
Effelsberg
Pulsar observations
at Effelsberg have a long history and cover a wide frequency range (800MHz
- 43 GHz). Our equipment enables us to make high quality radioastronomical
observations in all important aspects of pulsar study. Scatter broadening
of nine pulsars was investigated at over a wide range of frequencies with
the result that the broadening times are larger than predicted and follow
a flatter frequency dependence (n-3.4) than expected from standard
scattering theories. High precision pulsar timing observations enabled
us to determine the influence of spin-orbit coupling on the orbital parameters
of PSR J2051-827 and the radius of the companion. The Effelsberg radiotelescope
has excellent polarisation characteristics. A determination of rotation
measure for 46 pulsars enabled us to conclude, that no large scale reversals
of the magnetic field occur within 85°<l<245° and the magnetic
field follows the local spiral closely between 150°<l< 245°. Because
of our support for the common EPN Dataformat it has become easy and nearly
a routine matter to participate in simultaneous multifrequency-multitelescope
single pulse polarisation studies with our partners in Europe and India.
Investigating single Pulses of PSR B0329+54 simultaneously received in
Jodrell Bank and Effelsberg, it became evident, that between the two frequencies,
the centre component correlates strongly for circular polarisation but
not for linear polarisation, whereas both outer components exhibit the
converse behaviour. Pulsars show unexpected behaviour at the very high
radio frequencies (> 10 GHz) where they are still visible,- if only for
the Effelsberg Instrument. In a number of cases the received fluxes are
higher than expected, suggesting an up-turn in their spectrum. Furthermore,
their variability (modulation index) is higher than predicted, it is likely
that we observe intrinsic intensity variations at these frequencies. Observational
evidence is also at odds with canonical models of the magnetosphere: Radioemission
as observed could not escape a magnetosphere with the often assumed high
densities (>1000 nGJ) and Lorentz factors (g>100). Various forms
of curvature emission are often invoked by observers as an explanation
of radioemission. However the implied emission heights, Lorentz factors
and densities cannot explain the observed intensity of the radio emission.
The radial structure of radio emission region of pulsar
Xinji Wu
wuxj@bac.pku.edu.cn
Department of Astronomy,
Peking University
The study of radial
structure of radio emission region is important topic in the study of the
pulsars. The altitude of emission region cannot be derived directly from
observation. Emission altitude can be expressed as a function of frequency
. The method of the K parameter analyses was used to calculate the power
law index of altitude-frequency relation directly from observation data
at different frequency. The values of are obtained for 18 pulsars at two
frequencies of 610MHz and 1408MHz and for 3 pulsars at more than three
frequencies. The average value of power law index is 0.27, which indicate
the emission altitude increase with decreasing frequency and the radial
structure is compact.
The Observations of Mode-Changing Phenomenon of pulsars at UAO
Ali Esamdin
Urumqi Astronomical
Observatory, NAO, Urumqi 830011
Department of Astronomy,
Peking University, Beijing 100871
We reported the results
of pulsar mode-switching phenomenon observation obtained at 327MHz and
610MHz, using the 25m radio telescope of Urumqi Astronomical Observatory,
NAO. Several different shape of pulsar integrated profiles at two different
frequencies are presented. We also discuss some of the characteristics
of mode-changing in this paper.
Recent pulsar results from Parks
Dick Manchester
Dick.Manchester@csiro.au
ATNF, Australia
Not available yet!
Pulsar observations at Urumqi Observatory - present and future
Na Wang
wangna@ms.xjb.ac.cn
NAOC, Urumqi
We present the status
and results of pulsar observations in China. Observations commenced with
a pulsar timing system at the 25-m Urumqi Nanshan telescope in mid-1999;
these were the first regular and high-quality pulsar observations in China.
The center frequency of this system is 1540 MHz, and de-dispersion is provided
by a 2x128x2.5MHz filterbank/digitiser system. Observations over more than
one year have resulted in updated rotation parameters for 74 pulsars. Comparing
with earlier observations we showed that long-term period and period-derivative
fluctuations may be dominated by unseen glitches. Taking advantage of the
available telescope time, we are also monitoring the variation of pulsar
scintillation dynamic spectra for a few strong pulsars. Scintillation parameters
are measured and their variations are under study. We are planning to built
a new system at a lower frequency so that frequency-dependent pulsar properties
can be investigated.
An accretion disk model for periodic variations of
PSR B1828-11
Qiao G.J., Xue Y.Q, Xu R.X. Wang H.G., Xiao B.W.
xyq@water.pku.edu.cn
Astronomy Department, Peking University
Radio pulsar death
Bing Zhang
bzhang@astro.psu.edu
Pens, University
In this talk, I'll
review the recent progress in understanding the pulsar particle acceleration
and emission mechanisms, focusing on the polar cap scanario. I'll describe
how pair formation, an essential condition for pulsar radio emission, is
sustained in active pulsars through one photon pair production from both
the curvature and inverse Compton seed photons, or sometimes through two
photon production. In case of super-critical magnetic fields, some more
exotic processes, such as photon splitting and bound pair formation, will
be also discussed. These effects will be synthesized to discuss the radio
pulsar death both in the conventional long-period regime due to the turn
off the active accelerator, and in the high magnetic field regime (both
for high magnetic field pulsars and magnetars) due to the possible suppression
of the free pair formation.
A possible interpretation for the spectral behavior of pulsar average profiles
Wang, H.G. Qiao, G.J.
Xu, R.X.
wanghg@bac.pku.edu.cn
Department of Astronomy,
Peking University
Recently, Mitra &
Rankin (2002) identified three kinds of spectral behavior of pulsar average
profiles with conal component pairs: for the first two groups, the peak
separation or the pulse width exhibits pronounced narrowing as frequency
increases; for the third type, it shows almost no spectral change in separation
and width at all. In this paper we present a novel interpretation for these
phenomena. As to the first two types of behavior, our interpretation is
essentially different from the widely accepted explanation called "radius-to-frequency"
mapping, which suggests that lower radio frequencies are emitted at higher
altitudes. The implication towards the structure of emission region is
discussed.
The initial period of pulsars
Zhankui Huang
Department of Astronomy,
Peking University
The initial period
of pulsar are important to understand the process of the neutron star formation,
and the nature of equation of state of neutron star maters. There are two
ways of to determination. The theoretical one use the EOS to the possible
initial period, the other method is to presume the pulsar slow down by
magnetic dipole emission. The Chandra observation of Crab pulsar and Vela
pulsar give strong evidence that the nebula is symmetric about the spin
axis and the proper motion are parallel to this axis. If the coincidence
is common, then the processes that cause this coincidence are asymmetric
dipole emission. Based on this theory, we can use the proper motion data
to derive the initial period. The observed velocity of pulsars may be combination
of three factors that is the progenitor orbital velocity, the kick of asymmetric
explosion, and the off-center dipole emission. So we think the derived
value is the lowest limit of initial period.
Individual pulses of PSR J0437-4715
Xianghua Li
xhli@bao.ac.cn
NAOC
Not available yet!
Further investigation of the central beam of PSR B1237+25
Qiao,G.J.,Li,K.J, Wang,H.G.,Xu,R.X.
& Liu,J.F.
Astronomy Department,
Peking University
Core emission component
has been identified by observations (Rankin, 1983, Lyne & Manchester,
1988), which presents a challenge for various pulsar radio emission models.
Using Gaussian-components fitting, Qiao et al (2000) pointed out that the
central or core emission beam may be hollow. In this paper, by developing
a quantitative criteria for the fitting procedure, we prove that the mean
profile of the pulsar PSR B1237+25 is composed of six Gaussian components,
which confirms that the core beam is hollow. From the fitted results, further
information of the radio emission region is obtained based on the Invert
Compton Scattering model (ICS model). The Lorentz factor of secondary particles
for this pulsar is estimated to be 1000 ~3000.
Geometrical Analysis of Average Pulsar Profiles of PSR B1857-26
Huaxiang Wang
hxwang@water.pku.edu.cn
Urumqi Astronomical
Observatory, NAO, Urumqi 830011
Department of Astronomy,
Peking University, Beijing 100871
Applying the Gaussian
fit separation of the average profile (GFSAP) method, we examined the mean
pulse profile of PSR B1857-27 at five frequencies. This method provides
us important insight into the pulsar emission beam structure. As a result,
we calculated the opening angles and the emission altitudes. The spectral
difference between different parts of the emission region is apparent.
Benefiting from the separation, we are able to discuss the geometric properties
of the three emission zones: the core, the inner cone and the outer cone.
New Method for Magnetic Inclination Angle of Pulsar
Xuanbin Xu
Department of Astronomy,
Peking University, Beijing 100871
Magnetic inclination
angle is not only a basic parameter of pulsar, but also a key parameter
of polar cap model. There still have no perfect method to estimate this
parameter now. Several authoritative methods all need good polarization
measurement and profile datum. But in more than 1000 pulsars, there is
only a few part according it. It is great important how to expand the sample
of magnetic inclination angle for numerous theoretic and statistical research
subject. This paper first introduction several methods of estimating magnetic
inclination angle; and we analysis the polarization measurement of pulsars;
then we develop our new method. This method is based on the classification
of profile and the distribution of Q parameter for different class pulsars,
and it is applicable for those with bad linear polarization measurement
but good classification pulsars.
Radio jet in AGNs
D.R. Jiang, X.Y. Hong
and Xinwu Cao
Shanghai Astronomy Observatory
The talk present the
some results about the study of the radio jets in AGNs in Shanghai Observatory
group. The VLBI observations shown the supperluminal motion, the bending,
and probable rotation of the jets in some AGNs, the relationship between
the structure variation of the jet and the total flux density variation
is discussed. The multiband and multi-epoch VLBI observation of a sub-sample
EGRET sources shown there are some EGRET AGNs have a symmetric structure
at VLA scale, it is non consistent with the general idea that the EGRET
AGNs are strong beamed. The preliminary results of 7 intermediate BL Lac
objects (IBLs) suggested that the IBLs have the similar jet structure with
the RBLs (IBLs). We will briefly discuss the links between the radio jet
and the central engine.
Black hole masses and radio properties of Active Galactic Nuclei
Xue-Bing Wu{1}, J.L.
Han{2}, F.K. Liu{1}, T.Z. Zhang{1}
wuxb@vega.bac.pku.edu.cn
Parsec-Scale Rotation-Measure Distribution in 3C147 at 3.6 cm
Haiyan Zhang
hyzhang@bao.ac.cn
NAOC
VLBA polarization observations
of the steep-spectrum quasar 3C147 were made at four frequencies in the
available 8 GHz band. The distribution of the rotation measure of this
source was detected, which makes it possible to remove the Faraday screen
pixel-by pixel and obtain the intrinsic magnetic field structure of the
source.
VLBI observations of the quasar 0202+149 on scales from 0.5 mas to 0.5 arc
Weihua Wang
whwang@center.shao.ac.cn
Shanghai Astronomy Obervatory
Not available yet!
Thomson scattering effect on compact symmetric radio source OQ208
Xiang Liu
liux@ms.xjb.ac.cn
NAOC, Urumqi
The effect of Thomson
scattering in broad line radio galaxy OQ208 was investigated, it could
account for the large flux ratio of lobes in OQ208. And the effect for
other sources, e.g. NGC4261 is also discussed.
Detection of intrahour variations in quasar 3c273?
Xiang Liu
liux@ms.xjb.ac.cn
NAOC, Urumqi
A kind of quasi-periodic
intrahour radio variations pointing bright quasar 3c273 were detected at
6cm and 3.6cm bands using Urumqi 25meter radio telescope. We may estimate
a size around the accretion disk of the quasar if the detected variations
are intrinsic and outburst from the center.
The beaming mode for superluminal radio sources
J.H. Fan
jhfan@guangztc.edu.cn
Center for Astrophysics,
Guangzhou University, Guangzhou 510400, China;
National Astronomical
Observatory, CAS, Beijing, China;
CAS-PKU Astrophysics
Center, Beijing, China.
Relativistic beaming
model has been successfully used to explain the observational properties
in active galactic nuclei (AGNs). In this model the emissions are composed
of two compnents, namely, the boosted and the isotropic ones. But how much
is from each part is unknown. It is proposed that the luminosity in the
jet is proportional to the unbeamed one in the comoving frame, i.e., f=(L_{jet})/(L_{ub}).
However, the value of the ratio, f is not easy to determine. In this paper,
we used the beaming model and the radio sources with superluminal motions
(SM) to estimate the ratio for each source. log f = -2 to 3 is found.
The periodicity analysis of the radio loud blazars
R.G. Lin, J.H. Fan
jhfan@guangztc.edu.cn
Center for Astrophysics,
Guangzhou University, Guangzhou 510400, China
Based on the radio
data observed with the radio telescope in Michegon University. Periodicity
analysis was done using the Jurkevich method. To discard the false period
caused by the data distribution, Montel Carlo method is also used in the
analysis.
Highly polarized radio sources
JinLin Han
hjl@bao.ac.cn
NAOC
Not available yet!
Radio dichotomy of X-ray-selected AGNs
JiangHua Wu
jhwu@bao.ac.cn
NAOC
Quasars and AGNs are
traditionally devided as radio-loud and radio-quiet. Optically selected
AGN samples usually show bimodal distributions in radio-loudness. But recent
radio selected AGN sample (the FIRST Bright Quasar Survey) does not show
this radio dichotomy and tends to find radio-intermediate AGNs. Allowing
for the apparent selection effects in optically and radio selected AGN
samples, here we use an X-ray selected sample to readdress this question.
Jet formation and blazar evolutionary sequence
Xinwu Cao
cxw@center.shao.ac.cn
Shanghai Astronomy Observatory
I review the recent
progresses on the theories of jet formation. The relative importance of
the different jet acceleration mechanisms are compared. The physical implications
on the blazar evolutionary sequences are discussed.
Radio Supernovae
Zongwei Li
lizw625@sina.com
Astronomy Department, Beijing
Normal University
Not available yet!
Searching candidates of supernova remnant using radio survey data
X.Z. Zhang
zxz@bao.ac.cn
National Astronomical
Observatories, CAS, Beijing 100012,China
The MPIfR-CAS Group,
Beijing 100012, China
A supernova remnant
(SNR) usually consists of extended nonthermal radio emission. Most of them
show shell or partial shell structure, with an average spectral index of
$\alpha\sim -0.45 $ ($S \propto \nu^{\alpha}$). Because the emission is
produced by synchrotron process, it is usually (partially) polarized at
short wavelengths, though according to the Green catalog (2000), most SNRs
have a low degree of polarization at longer wavelengths. In a search using
NVSS data, Zhang et al. (2002) have found some candidate Galactic radio
sources,G41.9+0.04,G47.8+2.03, G74.8+0.63, and G93.2+2.63, with shell structure,
nonthermal spectrum, weak polarization, and no strong infrared emission
associated. In this contribution results of these four candidates are reported.
AIRE Plan in Tsinghua University
Jianfeng Zhou
zhoujf@tsinghua.edu.cn
Tsing Hua University
One big challenge that
modern astrophysicists should face is how to use Terabytes (maybe Perabytes
soon) of astrophysical database effectively. The proposed AIRE (Astrophysical
Integrated Research Environment) plan is to help astrophysicists solve
this problem. The AIRE is divided into three main parts. The first part
is automatic data searching and saving system. After one user input his/her
interested target, AIRE will automatically search and download all kinds
of relevant data (such as image, spectrum, lightcurve etc. ...) from tens
of web sites around the world. For some frequently used data, AIRE can
preserve a local copy. The second part is web-based astrophysical data
processing platform. Commonly used software like AIPS, DIFMAP, IRAF, HEASOFT,
CIAO, IDL, MATLAB, OCTAVE etc. will be installed in central server. Just
need a web browser, astrophysicists in different places, using different
computers and operating system can process the data in the server. The
third part is a concurrent project system (CPS). Under the help of CPS,
astrophysicists in different fields can pursue a collaborative reserch
efficiently.
Pulsar scintillation - probe of the interstellar medium
W. Sieber
sieber@fh-niederrhein.de
Hochschule Niederrhein,
University of Applied Sciences
Krefeld, Germany
It became clear shortly
after the detection of pulsars in 1967 that the intensity variations which
are characteristic for pulsar radio emission are at least partly due to
scintillation in the interstellar medium. Pulsars belong obviously to one
of the two classes of celestial radio emitters whose emission regions are
compact enough -defined in this case by the magnetosphere of the neutron
star - to show scintillation; some active cores of galaxies building another
class. The pulsed character of the emission of pulsars allows in addition
to determine the dispersion measure, i.e. the integrated content of electrons
along the line-of-sight to the source. This gives the possibility to estimate
individually the distance to each pulsar once a model of the distribution
of electrons in the Galaxy is known. Since both, the scintillation and
the dispersion measure, refer to the same thermal electrons, pulsars are
ideal probes of the turbulent electron component of the interstellar medium.
Moreover, these electrons cause Faraday rotation along the line-of-sight
in the presence of magnetic fields, giving clearly measurably effects in
the case of the often highly linearly polarised emission of pulsars. Pulsars
open up, therefore, the possibility to investigate the electron component
of the interstellar medium, especially its random density variations and
thereby the turbulence spectrum in parameter ranges, inaccessible to other
observations. The paper will show, what kind of measurements have succeeded
so far to analyse the turbulence spectrum, what parameter ranges have been
covered, what kinds of models have been discussed and in what directions
further investigations will go.
Theoretical Refractive Scintillation Simulations of Pulsars
Ai-zhi Zhou et al.
Department of Astronomy,
Peking University, Beijing 100871
Using the refractive
interstellar scintillation theory, we simulate the theoretical structure
functions for both the Kolmogorov spectrum and the super-Kolmogorov spectrum
of five pulsars at 610MHz and compare them with the observations. The theoretical
results for accord with the observations very well. This indicates that
the flux density variations observed for these pulsars are due to a propagation
effect-refractive scintillation-not to intrinsic variability. It provides
some evidence supporting the RISS theory and the extended medium model
and some information about the local interstellar scattering medium (LISM).
And it also gives some theoretical proof of the refinements of the models.
Evidence of geodetic precession in timing observation of binary pulsar PSR B1534+12
Biping Gong
bpgong@nju.edu.cn
Nanjing University
Not available yet!
Evolution of pulsar scale-height
Xiaohui Sun
xhsun@bao.ac.nc
NAOC
Not available yet!
Viewpoints of China on Millisecond Pulsar Timing
Ni Guangren Ke Xizheng
National Time Service
Center, CAS, Xi'an 710600
Recent research results of
pulsar timing in the world are introduced. Then the developments and viewpoints
of pulsar timing research in China are summerized. It is thought that the
time scale of millisecond pulsar is possible to be set up, and that pulsar
time and atomic time can be contrasted and verified by each other and developed
side by side. Long-term stability of the ensemble pulsar time is obviously
better than that of atomic time. In time scale research, the method of
wavelet analysis is superior to the conventional ones. Finally international
cooperation is suggested and the prospects of development layout of pulsar
time are presented.
Simulation of pulsar distribution in our Galaxy
Yingchun Wei
NAOC, Urumqi
Not available yet!
Quark Matter and Strange Stars
R. X. Xu
rxxu@bac.pku.edu.cn
Astronomy Department, Peking
University
The properties of quark-gluon-plasma
(QGP) in the standard model of particle physics are briefly reviewed. It
should be a great chance to study the quantum chromodynamical (QCD) nature
of strong interaction if we can have direct experiments or observations
of QGP. Beside the effort of creating quark matter in the relativistic
collisions of heavy ions, an astrophysical way to study QGP is to identify
strange quark matter (SQM, a kind of QGP with near equal numbers of light
quarks) as the residual after core-collapse type supernova explosion. Such
quark stars are simply called to be strange stars. Possible methods to
distinguish neutron stars and strange stars are presented.