Preliminary List of Chinese Participants Print E-mail

Douglas N. C. Lin

Douglas N. C. Lin

Institute: University of California Santa Cruz, Kavli Institute, Peking University

Title: The Kavli Institute for Astronomy and Astrophysics at Peking University

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Haojing Yan

Haojing Yan

Institute: Center for Cosmology and AstroParticle Physics, Ohio State University, USA

Title: Magellan High-redshift Lyman-Emitter Survey

Abstract: We have been undertaking a deep, multi-field, narrow-band imaging survey with IMACS to search for Ly emitters at z~6.5 and 7.0, which correspond to the last two OH-line-free windows accessible to CCD cameras. The survey aims to constrain the bright-end of the luminosity function, and to reduce the effect of cosmic variance as much as possible. The initial result from this on-going survey is reported here.

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Hu Zhan

Hu Zhan

Institute: Dept of Physics Univ. of California

Title: Science Opportunities with the Large Synoptic Survey Telescope

Abstract: The Large Synoptic Survey Telescope (LSST) will carry out a tremendously exciting survey, offering science opportunities from the solar system to the accelerating universe and opening the time domain for astronomy from tens of seconds to years in a systematic, mass-production mode. It is designed with four main science drivers: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. I will give a brief introduction of the LSST project and discuss various techniques for studying the accelerated cosmic expansion with the LSST.

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Li Guoliang

Title: Gravitational Lenisng Mass Reconstruction Algorithms for Galaxy Cluster

Abstract: Gravitational lensing is a powerful tool to detect the mass distribution in galaxy clsuters. The deep lens potential of galaxy cluster provides plenty of information to reconstruct surface mass distribution of cluster including weak and strong lensing signals. In this talk, I'll show some algorithms to do such reconstruction by differnt ways and give a summary.

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Liang Cao

Liang Cao

Institution: Shanghai Astronomical Observatory

Title: E/B decomposition of CMB polarization map

Abstract: We develop an algorithm of separating the $E$ and $B$ modes of the CMB polarization from the noisy and discretized maps of Stokes parameter $Q$ and $U$ in finite area. A key step of the algorithm is to take a wavelet-Galerkin discretization of the differential relation between the $E$, $B$ and $Q$, $U$ fields. This discretization allows derivative operator to be represented by matrix, which is exactly diagonal in scale space, and narrowly banded in spatial space. It makes this algorithm to be information loseless, and does not produce false correlations. We show that the effect of boundary can be avoided by dropping a few DWT modes located on or nearby the boundary. This method reveals that the derivative operators will cause large errors of the $E$ and $B$ power spectra on small scales if the $Q$ and $U$ maps are Gaussian noisy. However, the errors are rapidly decreasing with the increasing of scales. We test and demonstrate the algorithm with samples, of which the power ratio of $E$ and $B$ modes is of the order of $10^2$, and the signal-to-noise ratio is equal to 10 and higher. The results show that the DWT power spectrum of $B$ modes on scales larger than the finest scale by a factor of 4 and higher can be detected from noisy Stokes parameter maps $Q$ and $U$. Since wavelet variables contain information of both spatial and scale spaces, the developed method is also effective to recover the spatial structures of the $E$ and $B$ mode fields. Besides, the DWT variables can be used for various high order statistics.

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Li-Zhi Fang

Li-Zhi Fang

Institution: University of Arizona, USA

Title: Zeroth Law of Thermodynamics of Photon-Atom System and 21cm Cosmology

Abstract: A key physical process used in the 21 cm cosmology is the so-called Wouthuysen-Field effect, which is "take a gas in large container, …the photons, after an infinite scattering processes on the gas with kinetic temperature T, will obtain a statistical distribution over spectrum proportional to the Planck-radiation spectrum on temperature T. After a finite but large number of scattering processes the Planck shape will be produced in a region around the initial frequency." (Wouthousian, 1952) This statement actually is the zeroth thermodynamic law of a photon-atom system. Recently, we did a detail calculation on how a system of photons and atoms in early universe approaches to statistical equilibrium via resonant scattering. I will present the results, which shows some part of Wouthousian's statement is correct, and some part should be corrected.

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Qian Zheng

Qian Zheng

Institute: National Astronomical Observatories of China

Title: Contribution of Cross-Correlations to the 21cm Angular Power Spectrum in the Grey Ages

Abstract: Measurement of the 21cm hyperfine transition of neutral hydrogen provides a unique probe of the epoch of reionization and the Dark Ages. Three major mechanisms are believed to dominate the radiation process: emission from neutral hydrogen surrounding the ionized bubbles of first galaxies and/or quasars, emission from neutral hydrogen inside minihalos, and absorption of diffuse neutral hydrogen against the cosmic microwave background. In the present work we investigate the contribution of cross-correlation between these three components to the total 21cm angular power spectrum, in the sense that neutral hydrogen associated with different radiation processes traces the large-scale structures of underling density perturbations. While the overall 21cm power spectrum remains almost unchanged with the inclusion of the 21cm power spectrum remains almost unchanged with the inclusion of the cross-correlations, the cross-correlation plays a key role in the determination of the 21cm power spectrum during the transition of 21cm radiation from emission-dominated phase to absorption-dominated phase at redshift z≈20. A significant suppression of power in the 21cm angular power spectrum during the transition is anticipated as the result of negative contribution of the cross-correlation between the absorption of diffuse neutral hydrogen and the emission components. Therefore, an accurate prediction of the cosmic 21cm power spectrum should take the cross-correlation into account.

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Shuan Nan Zhang

Shuang Nan Zhang

Institute: Physics Department Tsinghua University, Beijing

Title:

  1. China's Future Space High Energy Astrophysics Missions (invited)
  2. Exact solutions for shells collapsing towards a pre-existing black hole (contributed oral talk)
  3. Contributions to WMAP cleaned temperature maps from SDSS galaxies: implications for the Planck mission (contributed oral talk)

Abstract:

  1. In this talk I will focus on China's Hard X-ray Modulation Telescope (HXMT) mission, which has been selected as China's first dedicated space astronomy mission. In addition to this mission, I will also describe several other mission concepts in high energy astrophysics under development for China's mid and long range plan of space science.
  2. Exact solutions for shells collapsing towards a pre-existing black hole (contributed oral talk) The gravitational collapse of a star is an important issue both for general relativity and astrophysics, which is related to the well known ``frozen star" paradox. This paradox has been discussed intensively and seems to have been solved in the comoving-like coordinates. However, to a real astrophysical observer within a finite time, this problem should be discussed in the point of view of the distant rest-observer, which is the main purpose of this paper. Following the seminal work of Oppenheimer and Snyder (1939), we present the exact solution for one or two dust shells collapsing towards a pre-existing black hole. We find that the metric of the inner region of the shell is time-dependent and the clock inside the shell becomes slower as the shell collapses towards the pre-existing black hole. This means the inner region of the shell is influenced by the property of the shell, which is contrary to the result in Newtonian theory. It does not contradict the Birkhoff's theorem, since in our case we cannot arbitrarily select the clock inside the shell in order to ensure the continuity of the metric. This result in principle may be tested experimentally if a beam of light travels across the shell, which will take a longer time than without the shell. It can be considered as the generalized Shapiro effect, because this effect is due to the mass outside, but not inside as the case of the standard Shapiro effect. We conclude that the concept of the ``frozen star" should be abandoned, since matter can indeed cross a black hole's horizon according to the clock of an external observer. Since matter will not accumulate around the event horizon of a black hole, we predict that only gravitational wave radiation can be produced in the final stage of the merging process of two coalescing black holes. Our results also indicate that for the clock of an external observer, matter, after crossing the event horizon, will never arrive at the ``singularity" (i.e. the exact center of the black hole). We also present a worked-out example of the Hawking's area theorem.
  3. Contributions to WMAP cleaned temperature maps from SDSS galaxies: implications for the Planck mission (contributed oral talk) We have systematically examined the cross-correlations between WMAP temperature maps, the SFD dust extinction map, and SDSS galaxies. We couclude that: (1) the dust extinction map is contaminated by emissions from SDSS galaxies, consistent with previous results; (2) SDSS galaxy number counts are significantly correlated with WMAP temperature maps before foreground cleaning, but the correlation still remains statistically significant even in the published cleaned maps; (3) the SDSS galaxy - WMAP correlations are best explained by contributions from unremoved and over-removed microwave emissions from SDSS galaxies, because the SDSS galaxies contamination to the SFD dust extinction map is not considered in the foreground cleaning process. Finally we will discuss the implications of our findings to the foreground cleaning of the Planck misison, which will sufer more from microwave emissions of galaxies.
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Xiang-Ping Wu

Xiang-Ping Wu

Institute: National Astronomical Observatories of China, Beijing

Title: Measuring the global signature of cosmic reionization with 21CMA

Abstract: The 21cm emission from neutral hydrogen in the epoch of reionization demonstrates a global component of T~10mK over the sky because of the homogeneity and isotropy of the universe. The difficulty of detecting this global signature is that foreground contamination should be suppressed by about 5 orders of magnitude and systematic variations should be controlled within 1mK in frequency domain. This poses a serious technical challenge to observational cosmology. We have conducted the measurement of the global 21cm emission with 21CMA for one year, based on a careful removal of systematic effect using polarization information. In this talk we will present our observational strategy and current constraint on the epoch of reionization.

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Xiangqun Cui

Xianqun Cui

Institute: Nanjing Institute of Astronomical Optics and Technology NAOC, Chinese Academy of Sciences

Title: LAMOST project and its current status

Abstract: Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is an innovative telescope project with both large aperture (effective in 4 meters) and wide field of view (5 degrees) to achieve the large scale spectroscopic survey observation. It is a meridian reflecting Schmidt configuration with a variable Schmidt optical system, realized by an active deformable corrector. For achieving such an ambitious project with limited budget, both its primary mirror (6.67m X 6.05m) and Schmidt plate (5.74m X 4.4m) are segmented. Telescope and 16 spectrographs with 4000 optical fibers in its focal plane have been completed in August of 2008. This presentation gives the general introduction on LAMOST and its current status, including its innovations, formidable technical challenges, preliminary results from the recent engineering test and preparing the scientific commissioning.

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Zhao Donghai

Insitute: Shanghai Astronomical Observatory, China

Title:

Abstract:

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