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The 6th Taipei Astrophysics Workshop
- Prospects in Astronomy and Astrophysics in the New Millennium
May 16-19, 2000
ASIAA, Taipei, Taiwan
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Abstracts

Hsiang-Kuang Chang, Dept. of Physics, National Tsing Hua Univ.

Magnetic Inclination of PSR B0656+14 Inferred from Its Thermal X-ray Emissions

The angle between rotation and magnetic axes of a pulsar has long been an important factor, but so far ill-determined, in accounting for its various appearances as observed in different energy bands. We devise a method to infer that angle, and the angle between observer's line of sight and the rotation axis as well, for pulsars whose X-ray spectrum has a good two-blackbody model fit. We present the result for PSR B0656+14 and discuss its implications on models for high-energy emissions from pulsars.

Alfred B.C. Chen, Natl Center Univ.

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Wenping Chen, Natl Center Univ.

Census of Kuiper-Belt Objects

Thus far some two hundred large (size more then 100 km) Kuiper-belt objects (KBOs) have been identified by direct imaging. Even smaller bodies, though expected to be more numerous on theoretical grounds, are much too faint to image directly. A KBO can reveal its existence, nevertheless, if it happens to block out the light from a background star. The Taiwan-America Occultation Survey (TAOS) project, a collaboration of the Lawrence Livermore Laboratory (USA), Academia Sinica, National Central University (both of Taiwan), and other institutes, aims to measure the frequency of such chance stellar occultations. Our experiment provides the only means to conduct the census of the Kuiper-belt population down to a few kilometer sizes. We are setting up an array of small (50~cm), wide-field (f/1.9) telescopes in Taiwan to monitor continuously the brightness of several thousand stars at a rate of 5 Hz. These robot telescopes will operate in a coincidence mode, so the sequence and timing of any candidate occultation event can be recorded and distinguished agaist a false detection. Other scientific byproducts, such as variable star studies, will conceivably also derive from this huge TAOS database, some 10,000 GB worth of photometrical measurements per year.

Kwong-Sang Cheng, Dept. of Physics, Univ. of Hong Kong

High Energy Radiation from Pulsars

We use a three dimension magnetospheric model to study the multi-waveband emission from pulsars. The observed light curves in various waveband and their phase-resolved spectra provide very important information about gamma-ray pulsars.

Eugene Chiang, Caltech

Dynamics of Eccentric Planetary Rings

The boundaries of several of the Uranian and Saturnian rings can be fitted by Keplerian ellipses. The pair of ellipses that outline a given ring are nearly perfectly aligned with each other. Apsidal alignment is surprising because the quadrupole moment of the central planet induces differential precession on extremely short timescales. Rigid precession of an eccentric ring has remained a problem in ring dynamics for over 20 years. I will propose that rigid precession is maintained by a balance of forces due to ring self-gravity, planetary oblateness, and interparticle collisions. Remarkably, collisional forces felt by material in the last 100m of a 10km wide ring can increase equilibrium masses up to a factor of 100. I will derive new ring surface densities that accord with Voyager radio measurements. Prospects for the Cassini Saturn orbiter will be summarized.

Tzihong Chiueh, NTU/ASIAA

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Wenchien Chou, ASIAA

Dynamics of the Parker-Jeans Instability in a Galactic Gaseous Disk

Linear analysis and non-linear 3D simulation of magnetohydrodynamics of a gas layer are carried out in local co-rotating coordinates, taking into account the effect of self-gravitational force and shearing rotation. The gas is subject to the Jeans instability when there is no magnetic field, or to the Parker-Jeans instability when a magnetic field is present. We study the evolution of these instabilities in several cases which vary in factors such as the rotational speed, shearing rate, strength of magnetic fields, external pressure, external gravitational force, and directions of perturbations. We find that the growth rate of the instabilities and the shape of the dense blobs that aggregate in the nonlinear stage depend sensitively on these factors. When we adopt typical parameters of nearby molecular clouds, we find that the gas forms coherent long filaments with a separation of about 5pc. This agrees with observation. This suggests that molecular clouds with a coherent filamentary structure may be attributed to the Parker-Jeans instability of a gaseous disk under the influence of rotation. This study sheds light on how interstellar/intergalactic gas aggregates to form molecular clouds and seeds of stars, and thus on the star forming process at its very early stage.

Yaoquan Chu, Univ. of Sci. & Tech. Of China, Hefei

The LAMOST project

In China, we now start to build a new spectroscopic survey telescope. It will be a meridian reflecting Schmidt telescope. The optical system is horizontal. The primary mirrors is spherical and segmented. It faces towards the north. In its spherical center there is a plane mirror which is segmented too. The different shape of reflecting Schmidt plate is realized by active optics. The clear aperture is 4m and f-ration is 5. The angular field of view is 5 square degree, 4000 objects can be observed simultaneously by using optical fibre. The science goal is to make a 20000 square degrees spectroscopic survey, including ten million galaxies and stars, many variable objects and the identification of numerous objects found by radio, x-ray, IR and other survey in this sky areas.

Wei Cui, MIT

Probing Relativistic Effects around Black Holes and Neutron Stars

I will review the basic ideas recently proposed for studying general relativistic effects around stellar-mass black holes and neutron stars, based on X-ray observations of binary systems that contain such objects.

Longlong Feng, Center for Astrophysics, Univ. of Sci. and Tech. Of China

Non-Gaussianity and the recovery of the mass power spectrum from Lyman-alpha forest

The non-Gaussianity of the cosmic density field could be the dominant source of error and inevitably leads to the information loss in power spectrum analysis. In this article, the effect of non-Gaussianity on the reconstruction of the initial mass field from the Lyman-alpha forest is investigated. It is shown that the non-Gaussianities such as skewness, kurtosis and scale-scale correlation can not be completely removed by the conventional algorithm of Gaussianization. To eliminate the effect of non- Gaussianity, two methods are proposed. The first is to perform the Gaussianization scale-by-scale using the discrete wavelet transform (DWT) decomposition. We show that the non-Gaussian features of the Lyman-alpha forest basically will no longer exist in the scale-by-scale Gaussianized mass field. The second method is to choose a proper orthonormal basis (representation) to suppress the effect of the non-Gaussian correlations. In the quasilinear regime of cosmic structure formation, the DWT power spectrum is efficient for suppressing the non-Gaussian contamination. These two methods significantly improve the recovery of the mass power spectrum from the Lyman-alpha forest.

Yu Gao, IPAC/Caltech

A High Velocity Collision Induced Starburt in Intragroup Medium

Here we report the detection of a bright starburst in the intragroup medium (IGM) of the famous compact group of galaxies "Stephan's Quintet". This burst is triggered by a collision between a high velocity ($\delta$\sim$1000km/sec) intruder galaxy (NGC7318b) and the cold IGM of the group. We present nes ISO mid-infrared (15$\mu m$ and 11.4$\mu m$) and far-infrared (60$\mu m$ and 100 $\mu m$) observations along with new ground-based \alpha$ and ('$-band) images, BIMA CO(1-0) observations, VLA 20cm contimuum images and SCUBA sub-millimeter observations. This is the first known starburst that is induced by a galaxy+cold-IGM collision. It provides new constraints on theories about interaction-induced starbursts, and may hint at a new mechanism for the star formation excess seen in more distant clusters."

Xiangtao He, Dept. of Astronomy, Beijing Normal Univ.

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Luis C. Ho, Carnegie Observatories, USA

Supermassive Black Holes and Galaxy Evolution

Supermassive Black Holes and Galaxy Evolution; The Magellan Project: Future Prospects for Optical-Near-Infrared Astronomy in the Southern Hemisphere"

Cheng Wynn Ho, Cornell Univ.

Neutron Stars

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Rue-Ron Hsu, Natl Cheng Kung Univ.

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Jiasheng Huang, Harvard Smithsonian Center for Astrophysics

Extragalactic surveys with SIRTF

The mid- and far-IR extragalactic surveys with SIRTF will allow us to detect galaxies at z>2, the "dark age" of observational astronomy. In this talk, I will focus on the GTO survey programs with the 3 cameras on SIRTF, and their impact on studing galaxy formation and evolution at both high and low redshifts.

Chorng Yuan Hwang, Natl Center Univ.

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Ing-Guey Jiang, ASIAA

The Dynamics of Small-N Body Systems

The periodical solutions of three or four body systems are investigated and thus the stability of these systems are studied. This investigation leads to two applications: (1)The existence of long-lived belts for discovered planetary systems. (2) The enjection of brown dwarf stars.

Yipeng Jing, Univ. of Tokyo

Studying galaxy formation with high-resolution simulations

Some of our recent results from high-resolution cosmological, individual halo, and hydro/N-body simulations are presented.

Sun-Kun King, ASIAA

The Occultation Event Rate of Kuiper Belt Objects: A Simple Geometric Consideration

From a single-power-law size distribution and a solar disk model, we estimate the occultation event rate of Kuiper belt objects based on assumptions of simple geometric arrangement. Detection limit (e.g. diffraction limit) in an occultation survey such as TAOS project is taken into account. A special case of distribution of occultation duration was also derived. Its implication is discussed.

Chao-Lin Kuo, Univ. of California at Berkeley

ACBAR: A CMB Experiment at the South Pole

The ACBAR (Arcminute Cosmology Bolometer Array Receiver) is a multi frequency band (150, 214, 275, 350 GHz), high angular resolution (4 arcminute FWHM), high sensitivity (250 mK.rsec) instrument of cosmology purpose. Performance of ACBAR in several aspects - anisotropy power spectrum, SZ cluster search, and the detection of SZ kinematic effect - is assessed.

Dong Lai, Cornell Univ.

Core-Collapse Supernovae and Neutron Star Formation

Despite decades of theoretical investigations, our understanding of core-collapse supernovae remains significantly incomplete. Recent observations show that many supernovae are asymmetric and newly-formed neutron stars have large space velocities. I will discuss the physics of different mechanisms for generating asymmetric explosions and pulsar velocities, including hydrodynamically driven, neutrino and magnetically driven kicks.

Jeremy Lim, ASIAA

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Guey-Lin Lin, NCTU

Astrophysical processes in an intensive background magnetic field

We provide a new approach for computing astrophysics related processes such as photon splitting \gamma -->\gamma\gamma, pair production \gamma e^+ e^-, and gamma--> u\bar{ u} in a strong background magnetic field. Compared to previous studies, much simpler amplitudes are obtained for the above processes.

Jinzeng Li, Natl Center Univ.

Optical identification of ROSAT-selected WTTS at high-Galactic latitudes

Huan Lin, Steward Observatory, Univ. of Arizona

Application of CNOC2-Calibrated Photometric Redshifts in Measuring Galaxy Evolution

Using the NOAO Mosaic CCD camera, we have carried out BVRI imaging of 6 sq. degrees in and around the CNOC2 Fidld Galaxy Redshift Survey, in order to obtain a well-calibrated photometric-redshift sample of some 40000 R<21.5 galaxies. We will present results on photometric redshift calibration and luminosity function (LF) measurement, and will demonstrate the viability of using our photometric-redshift sample to constrain LF evolution parameters.

Sheng Yuan Liu, Caltech

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Kwok-Yung Lo, ASIAA

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Nanyao Lu, IPAC/Caltech

Mid-IR Emission of Galaxies (tentative)

Will present and discuss results of ISO spectroscopic observations of galaxies

Chung-Pei Ma, Upenn

An Analytical Model for Nonlinear Gravitational Clustering

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Ue-Li Pen, CITA and ASIAA

Cosmology with the Moving Mesh Hydro Code

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Bo Peng, National Astronomical Observatories, China

The Proposed World's Largest Single Dish, FAST

A Five hundred meter Aperture Spherical Telescope (FAST) is proposed to be built in the unique karst area of southwest China, and will act, in a sense, as a prototype for the Square Kilimeter Array (SKA). It will be over twice as alrge as Arecibo coupled with much wider sky coverage. Some results from site surveys for such a SKA concept are briefly reported. Technically, FAST is not simply a copy of the existing Arecibo telescope but has rather a number of innovations. Firstly, the proposed main spherical reflector, by conforming to a paraboloid of revolution in real time through active control, enables the realization of both wide bandwidth and full polarization capability while using standard feed design. Secondly, a feed support system which integrates optical, mechanical and electronic technologies will effectively reduce the cost. With an overall diameter of 500m and radius of its spherical surface of 300m, FAST will be the world's largest single dish. The FAST will be especially effective in deep surveys for sources such as rare types of pulsars and neutral hydrogen clouds at moderately high redshifts. FAST as a VLBI station will be the hub of the most highly sensitive network. FAST will play an important role in the deep space network, and in SETI searches.

Chien Y. Peng, Steward Observatory, Univ. of Arizona, USA

The Host Galaxies of Gravitationally Lensed Quasars

Gravitational lensing has been used to study quasar host galaxies at fainter limits than direct imaging of non-lensed quasars. Lensing enhances the host galaxy detections by magnifying and stretching the light into arcs and rings, away from the bright quasar images. To date, results from the CfA/Arizona survey (CASTLES) to study lenses with HST show that the hosts of radio-quiet quasars (RQQ) at z~2 mostly have modest to low luminosities (L<L_*). Compared to low redshift RQQ, z~2 host galaxies harbor a more massive central black hole at a given host mass, suggesting that the black holes grew more rapidly than their host galaxy at early epochs. Finally, we discuss the host galaxy morphology and stellar content based on color images from the survey.

Hsien Shang, CfA/ASIAA

Multiwavelength Diagnostics of Jets from Young Stars

Multiwavelength study of the jet phenomena from young stars are becoming the key tests to compare theories and observations. I will present efforts made by our group to decipher physical conditions in such objects with theoretical first-principle modeling.

Yao Huan Tseng

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Daniel Qingde Wang, Astronomy Dept. Univ. of Massachusetts

X-ray observations of nearby galaxies

X-ray investigation of nearby galaxies is essential to our understanding of high energy phenomena and their relation to galaxy evolution. Recent observations with ROSAT, ASCA, and Chandra have allowed for detailed imaging, timing, and spectral studies of various X-ray sources and their relation to other galactic components. I will review some of the results and will discuss their implications.

Zhong Wang, Center for Astrophysics, U.S.A.

Submillimeter Observations From A Small Satellite: Recent Results

The Submillimeter Wave Astronomy Satellite (SWAS) mission has been in successful operation since December 1998, opening up one of the last previously unexplored wavelength window in astronomy. The main goal of this mission is to perform both survey and pointed observations of dense molecular clouds within our galaxy in either ground-state or a low-lying transition of five important species: H_20, H_2^{18}O, O_2, CI and ^{13}CO. I report on some significant findings of this mission, including the prominent and ubiquitous water line emissions from molecular clouds and shocked regions in the interstellar medium.

Jiun-Huei Proty Wu, Astronomy Dept. Univ. of California at Berkely

Detecting Non-Gaussianity in the CMB

We investigate the test of non-Gaussianity in the CMB as a technique for distinguishing between different models of structure formation. Two different methods are proposed: one being capable of extracting the non-Gaussian signal from a very strong Gaussian background, and the other being sensitive to scale-scale correlations which are generically expected in defect models. A review of this fild and an update of the current status of different models will also be summarized.

Yanqin Wu, CITA, Toronto

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Haiguan Xu, Dept of Applied Physics, Shanghai Jiao Tong Univ.

Hard Excess X-rays from Galaxy Groups/Clusters

Hard excess X-rays beyond the thermal emission component was found from the galaxy clusters in the past few years and from the galaxy groups recently. In this talk, I briefly review the results of the related studies, both observational and theoretical, and introduce our model using the inverse comptonization of the ICM photons in the intra-cluster medium.

Dr. Wenli Xu, Landessternwarte Heidelberg

LUCIFER - a NIR Spectrograph and Imager for the LBT

LUCIFER is a cryogenic near infrared imager and spectrograph for the Large Binocular Telescope which will support seeing and diffraction limited direct imaging, seeing and diffraction limited long-slit spectroscopy, integral field spectroscopy and (in small fields) OH-suppressed imaging of very faint objects. The instrument concept and preliminary optical design are presented.

Yong-Qiang Yao, Okayama Astrophysical Observatory, Natl Astronomical Observatory of Japan

NIR-revealed Deeply Embedded Sources and Multiple outflows toward the youngest clusters

Near infrared K-band polarimetric images and the narrow-band H$ images will be presented for the molecular outflow regions, IRAS20050, IRAS20126, IRAS20188, S233, GL5180, and GL6366S. All the regions exhibit reflection nebulae associated with massive/clustered star formation. The polarimetric patterns in each region reveal the deeply embedded sources (DESs) which significantly illuminate surrounding nebulosity but are not detectable on the intensity images. The compilation of DES observations over a large wavelength range suggests that the polarimetric DESs possess similar characteristics to hot molecular cores, and are likely to be in the pre-UCHII phase. The H$ images serve as another tool for revealing DESs, and furthermore the shocked H$ emission provides a unique census for outflow activities in the clusters. In particular, multiple non-axially symmetric H$ shocks are significantly detected in S233 and IRAS20050. Five H$ flows are found to be emanating from the S233:DES area, and six H$ flows to be associated with IRAS20050:DES subcluster with a flow structure consistent with the multiple CO outflows. Both the regions show a remarkable feature that violent H$ outflows are strongly associated with the most deeply embedded, i.e., the youngest clusters. The significance of NIR-revealed DESs and multiple H$ flows will be discussed toward clustered star formation.

Howard K.C. Yee, Univ. of Toronto

High-Redshift Galaxy clusters: Cosmology and Galaxy Evolution

High redshift galaxy clusters provide powerful constraints to cosmological models and scenarios of galaxy formation and evolution. I will describe a large 100sq deg optical imaging survey using the new generation of wide-field mosaic CCDs at CFHT and CTIO to generate a complete sample of rich galaxy clusters at redshift between 0.4 and 1.4. This survey will produce by far the largest high-redshift cluster sample. Some preliminary results and their implications will be presented. Also, future plans for detailed studies of amny aspcts of cluster properties, dynamics, and evolution will be discussed.

Qizhou Zhang, Harvard-Smithsonian Center for Astrophysics, USA

Observational Studies of High-Mass Star Formation

TBA

Shuang-Nan Zhang, Univ. of Alabama in Huntsville

Uncovering the Masks around the Black Holes in X-ray Binaries

We present our recent results on extensive analysis and modeling of X-ray data on several black hole X-ray binaries, obtained from several space borne high energy astrophysical instruments. Our results allow us to determine the properties of the black holes and the detailed structure of the accretion disks around them. In particular the angular momenta of the black holes are estimated for the first time and a three-layered atmospheric structure around the black holes has been discovered recently.

Dr. Zhou Xu, Beijing Astronomical Observatory

Large Field Multicolor Studies of Abell 566

Abell566 is a nearby galaxy of Z=0.1. The CCD images of BATC large field multicolor photometric system can cover the whole galaxy cluster and give spectral energy distribution (SED) of all the sources in field of Abell 566. By using BATC data on field of Abell566, following main study result on Abell 566 are: (1) Base on characteristic of morphology and spectral energy distribution, we have successfully separated the member galaxies of galaxy cluster Abell566 from field star and field galaxies. The estimated total number of the member galaxies is more than 700. That include about 400 galaxies have high reliability of membership. Before our work, the total number of member galaxies only 100 to 200 galaxies and only very few of them are identified. (2) The special distribution of red and blue galaxies are very different. The red galaxy include elliptical and early type spiral galaxies. The blue galaxies are the galaxies of other types. The red galaxies are much more condensed in center of the cluster than blue galaxies. (3) By a galaxy evolutionary model attribute by Arimoto, we analyzed the evolutionary relation among the member galaxies of the galaxy cluster.