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Activity > Colloquium

Colloquium (2008)

ASIAA Colloquium is usually held on Wednesdays at 2:20-3:20 pm in Room 1203 of the Astronomy-Mathematics Building, NTU. All scientists are welcome to attend.

The ASIAA-NTU joint colloquium series aims to bring to the physics/astronomy/cosmology community in ASIAA/NTU world renown researchers who will talk about the forefront development of physical sciences.

Contact: Colloquium Committee (talks_replace2@_asiaa.sinica.edu.tw)

No. Time/Place Speaker Topic / Abstract
download PDF: download talk PDF file
12008-12-23 Tue
10:30~11:30
R716
Dr. Chow-Choong Ngeow
[UIUC]
From Cepheids to the Dark Energy Survey
Abstract

Determining the Hubble constant and the understanding of recently discovered dark energy are two (out of many) of the main problems in astrophysics. The traditional way to determine the Hubble constant is through the cosmic distance ladder. One important rung on the distance ladder is the Cepheid Period-Luminosity (PL) Relation. In this talk I will talk about the recent finding of non-linear PL relation and it effect on the Hubble constant. On pursuing the dark energy, I will give an overview of the project I'm currently involved, the Dark Energy Survey (DES), and focus on the data management for the DES project.

22008-12-19 Fri
14:00~15:00
R716
Prof. Andreas Albrecht
[UC Davis]
Dark Energy: Current theoretical issues and progress toward future experiments
Abstract

The cosmic acceleration is widely regarded as one of the most exciting recent scientific developments. Many expect that radical changes to our understanding of fundamental physics will be required to understand the mystery of the cosmic acceleration (supposedly driven by the "Dark Energy"). Interestingly, new experiments are within reach that could have a tremendous impact on this very data-driven field. In this talk I will review some of the key theoretical issues and then discuss some of the opportunities presented by future experiments.

32008-12-18 Thu
15:00~16:00
R833
Prof. Myungshin Im
[Seoul National University]
Supermassive Black Holes of Quasars at World's End
Abstract

I will outline the recent works we have carried out to understand the nature of supermassive black holes (SMBHs) at high redshift (4.5 < z < 6.4). SMBHs are black holes with masses of order of 10^6 - 10^10 M_sun, residing at the centers of quasars and massive spheroids. Using the AKARI space telescope's unique NIR spectroscopic capability, we have obtained the rest-frame optical spectra of high redshift QSOs for the first time. This enabled us to trace the evolution of SMBHs out to z ~ 6.22 using a reliable mass estimator based on H-alpha line. I will show our findings based on a pilot survey data, and also introdue an ongoing mission program QSONG. We will also introduce Intermediate-wide, Medium-deep Survey (IMS) in NIR to extend the study of quasars beyond z > 6.5, and discuss possible ways to form a collaboration with Taiwanese astronomers in this area of research.

42008-12-18 Thu
16:00~16:30
R833
Prof. Soojong Pak
[Kyung Hee University]
NIR high spectral resolution spectrometer
52008-12-12 Fri
14:00~15:00
R716
Dr. Francois Viallefond
[Paris Observatory]
The origin of the radio recombination lines in the starburst M82 using VLA and IRAM-PdB observations
62008-12-11 Thu
14:00~15:00
R716
Prof. Frank Shu
[UC San Diego]
Energy Strategy for Taiwan
72008-11-18 Tue
14:00~15:00
R716
Prof. Masahiro Takada
[IPMU, Tokyo University]
Neutrino Mass and Cosmology
82008-10-24 Fri
14:00~15:00
R716
Dr. Hua-bai Li
[CfA]
Magnetic Fields versus Turbulence in Molecular Clouds
Abstract

The biggest open questions in star formation concern mechanisms that oppose gravitational collapse and regulate star formation. While turbulence and magnetic fields are almost ubiquitous in molecular clouds, their relative importance is often the key contrasting assumption between the major star formation theories. Using multi-wavelength and multi-scale polarimetry observations from JCMT, CSO, and SMA, we present observational evidence of magnetic fields being a crucial player over a large range of scales. I will also introduce a new method which allows us to probe the magnetic field and turbulence in molecular clouds at the same time.

92008-10-03 Fri
14:00~15:00
R716
Dr. Hsiao-Mei (Sherry) Cho
[National Institute of Standards and Technology, USA]
Cosmology and Ubiquitous Superconducting Sensors
Abstract

Precision measurements of cosmological parameters can benefit from large-format sensor arrays to increase the sensitivity. This requirement has been met by the development of microfabrication techniques for the production of a large number of superconducting sensors. The superconducting sensor, voltage-biased at its transition, is over an order of magnitude more powerful than conventional sensors. The readout of many detectors has been developed utilizing superconducting quantum interference devices (SQUIDs). As a result, such large format superconducting sensor arrays combined with SQUIDs readout has enabled many experiments and observations that were previously impossible. APEX-SZ and SPT, experiments to search for galaxy clusters via the thermal Sunyaev-Zel’dovich (SZ) effect at millimeter wavelengths, are projects that I worked at UC-Berkeley. Both projects employ frequency-domain SQUID multiplexing of signals from an array of superconducting transition-edge sensors (TES). APEX-SZ was deployed to Atacama, Chile in 2006 and SPT South Pole in 2006. Preliminary results from both projects will be presented. At NIST, we have been developing TES for many different astrophysics projects, including polarimeters for measuring the polarization of the cosmic microwave background with the goal of detecting the signature of inflation, galaxy cluster surveys with the SZ effect to constrain the equation of state of dark energy, and studies of large-areas of the Galactic plane and mapping the internal structure of SZ clusters. These TES arrays are a leading candidate for x-ray measurements with international x-ray observatory to reliably measure the mass of galaxy clusters as a further constraint on dark energy. In addition, we provide time-domain SQUID readout as well as SQUIDs to many astronomical experiments.

102008-09-30 Tue
14:00~15:00
R716
Professor Laird Thompson
[University of Illinois]
Detecting the Atmospheres of Extrasolar Planets
Abstract

Spectroscopy of transiting extrasolar planets has the potential of revealing the detailed nature of many extrasolar planetary atmospheres. Broad spectral energy distributions are available for two extrasolar hot Jupiters (HD 209458b and HD 189733b) from Spitzer, and an extended high dispersion optical spectrum exists only for HD 209458b. After many attempts to obtain other high dispersion spectra of transiting planets (on STIS/HST, HET, Keck, Subaru), it is clear that we face many challenges. In my talk I will discuss transiting extrasolar planets, what we know so far about their atmospheres, and describe the design of a new high dispersion spectrograph for CFHT capable of detecting the atmospheres of many more transiting extrasolar planets.

112008-09-23 Tue
14:00~15:00
R716
Dr. Ming-Chang Liu
[ASIAA/CIW]
Short-lived radionuclides, early solar system chronology and chemical evolution
Abstract

Origin(s) of short-lived radionuclides (t_{1/2} ˜ 100My) has been a long-standing interest in cosmochemistry. An understanding of how short-lived radionuclides could have been distributed in meteoritic refractory inclusions, which is of key importance to trace the origin(s), helps elucidate their distributions in the solar nebula. In addition, their short half-lives could potentially help us establish the high resolution chronologies for early solar system evolution if their origin(s) are well determined. Hibonite (CaAl$_{12}$O$_{19}$) is believed to be one of the earliest solids in the solar system, which occurred as either direct nebula condensates or refractory residues after distillation. Therefore, studies of short-lived radionuclides along with stable isotopes in these inclusions would provide constraints for the earliest environment and chemical evolution of the solar system. In this talk, I will be reviewing some literature data and presenting the results of the latest isotopic studies on 41Ca, 26Al, 10Be, oxygen and titanium in hibonite grains to discuss their implications for the origin(s) of short-lived radionuclides, early solar system chronologies and chemical evolution.

122008-09-16 Tue
13:00~14:00
R716
Prof. Richard Hills
[Cambridge]
ALMA - Its Current Statue and Future Promise
132008-09-12 Fri
14:00~15:00
R716
Dr. Oscar Morata
[ASIAA]
Clumps and time-dependent chemistry in dense cores
Abstract

I will show a review of some of the work I have done in my main line of investigation. The comparison of the different emission properties of high-mass density tracers (such as CS and NH3) in dense cores of molecular clouds led us to propose a model that explains the differences as a result of time-dependent chemistry and the existence of unresolved transient clumps with a typical lifetime of about 2Myr. The model has specific predicions for the chemical properties of the gas and provides us with the tools to test it with further observations. I will show some published results that support the existence of these transient clumps, recent refinements of the chemical models and new unpublished results.

142008-08-29 Fri
14:00~15:00
R716
Dr. Sandor Molnar
[ASIAA]
Constraining Intra-cluster Gas Models with AMIBA
Abstract

The major difficulty in using clusters for cosmology is in the determination of the physical properties of the intra-cluster gas (ICG) out to the virial radius. At present we can observe the ICG only in the inner part of clusters using X-ray satellites. We discuss how we can improve on our understanding of the ICG at large radii using AMiBA.

152008-08-08 Fri
14:00~15:00
R104
Professor Frank Shu
[UC San Diego]
Global Change and the Energy Crisis: Analyses and Solutions
Abstract

We analyze the implications of the recent G8 targets on the reductions in carbon dioxide emissions for 2050 in terms of the changes needed in global and local energy usage. We then review in a first principles manner the physics behind biofuels, photovoltaics, wind, surf, geothermal, tides, hydroelectric, nuclear fission, and nuclear fusion as alternative energy sources to fossil fuels. We demonstrate why only an aggressive expansion of nuclear power plants can meet the 2050 G8 goal, although photovoltaics holds promise as a long-term resource if costs can be driven down enough so that their installation on a large scale does not eat up almost half of worldwide GDP. Even if cost were not a factor, land use dictates that nuclear power is the only viable, carbon-friendly, choice possible for Taiwan. We analyze the plan put forward by Greenpeace and the European Renewable Energy Council and show that the use of only renewable energy sources to meet the G8 goal would cause massive harm to the natural environment and still be unresponsive to the economic aspirations of developing nations. We present new ideas in nuclear power technology that can address legitimate concerns about its cost, safety, waste, and potential for weapons proliferation. We summarize by giving a coherent energy strategy that can appeal to developed and developing nations alike, but that requires environmentalists and nuclear activists to work together for a safer and healthier world.

162008-07-11 Fri
14:00~15:00
R716
Dr. Anita Richards
[]
MERLIN/VLBI maser measurements of M-stars' mass loss
172008-07-04 Fri
14:00~15:00
R716
Dr. Tzu Ching Chang
[ASIAA]
21cm Cosmology
182008-06-20 Fri
14:00~15:00
R716
Dr. Patrice Theule
[Universite de Provence]
Interstellar ice analogues thermal and photo reactivity in laboratory: Reactivity in RNH2:CO2:H2O ices
Abstract

This talk will address the recent work we carried out in the astrochemistry group at the University of Provence in Marseille, France. Chemical reactivity on interstellar grains is studied in laboratory using infrared spectroscopy. We study the chemical evolution of a mixing of simple molecules as detected by the ISO telescope. We show that a NH3:CO2:H2O mixing thermally evolves to give ammonium carbamate, and that a CH3NH2:CO2:H2O mixing evolves into methylammonium methylcarbamate. Once irradiated by VUV light this species evolves into glycinate, the salt of glycine. Warmed-up the glycinate evolves into the zwitterionic form of glycine, which can be released into the gas phase of the ISM.

192008-06-13 Fri
14:00~15:00
R716
Dr. Sergei A. Levshakov
[Ioffe Physico-Technical Institute, Russia]
QSO spectra in cosmological tests
Abstract

Current status of spectral observations of quasars will be given in regard with two cosmological tests related to the nature of dark energy: the scaling law for the Cosmic Microwave Background Temperature evolution with cosmological redshift z, and the variability of the fine-structure constant alpha. Astronomical constraints on the modification of the linear behavior of T(z) as predicted by Lambda-decaying models and on variations of alpha will be considered. New tests to probe the variability of alpha based on spectral observations in mid- and far-IR regions will be discussed.

202008-06-06 Fri
14:00~15:00
R716
Dr. Youhei Masada
[ASIAA]
A Key Process for Magnetohydrodynamic Phenomena in Astrophysical Compact Objects
212008-06-04 Wed
14:00~15:00
R716
Prof. Josh Barnes
[University of Hawaii]
Identikit 1: A Modeling Tool for Interacting Disk Galaxies
Abstract

Galaxy mergers are a fundamental aspect of galactic evolution. While the dynamics of mergers can easily be reproduced by numerical simulations, few of the many ongoing mergers we observe have been modeled in any detail. I describe a new approach to navigating the parameter space of galactic collisions and finding initial conditions which reproduce the observed morphology and kinematics of merging galaxies. The method is tested on a random sample of galactic collisions; in many cases it accurately recovers the initial conditions of these encounters.

222008-05-28 Wed
13:30~14:30
R716
Prof. Frank Shu
[UC San Diego]
The ISM of Nearby Galaxies and the Future of the SMA
Abstract

TBA

232008-05-23 Fri
14:00~15:00
R716
Dr. Yoichi Ohyama
[ASIAA]
AKARI Mid-infrared Spectroscopic Views of Galaxies out to z~0.5
Abstract

It has been realized since ISO that there are numerous faint galaxies seen at mid-infrared (MIR), and they are so numerous that strong evolution in luminosity and/or space density at z=0.3-2 has been discussed. It has also been realized that PAH (Polycyclic Aromatic Hydrocarbon) emission contributes significantly to the observed MIR flux. Since the PAH emission is known to trace star formation activity, investigation on their MIR activity and especially on their strong PAH emission could be essential in understanding galaxy evolution at mid-z universe (z=0.3-2). The InfraRed Camera (IRC) onboard AKARI (formerly ASTRO-F) is a camera and a spectrograph covering NIR-MIR. This instrument is very unique so that one can perform sensitive wide-field (about 10x10 arcmin2) slit-less spectroscopic surveys over wide wavelength range (2-26um). To exploit this unique capability, we have been conducting a blank-sky deep MIR slit-less spectroscopy survey, the 'SPICY' (='S'pectrosco'pic' Surve'y' of galaxies) project, to provide excellent sample of faint MIR galaxies for examining galaxy evolution at z~<0.5. Main benefits of this survey are direct determination of redshift and targets' activity (by analyzing spectral features), and fair sampling of objects (with little selection biases). So far, observations have been conducted over 11 fields, and we have successfully obtained spectra of faint objects down to 1 mJy or even less at 5-26um. In this colloquium, I will present our spectra and analyses on their spectral and broad-band photometric characteristics, and discuss their nature.

242008-05-22 Thu
14:00~15:00
R716
Prof. Frank Shu
[UC San Diego]
Magnetized Star Formation: Disks, Jets, and Funnel Flows
Abstract

TBA

252008-05-16 Fri
15:30~16:30
R716
Prof. Ryohei Kawabe
[Nobeyama Radio Observatory]
Recent progress and future plan of Nobeyama Radio Observatory (NRO)
262008-05-09 Fri
14:00~15:00
R716
Dr. Huirong Yan
[CITA]
Nonlinear Cosmic ray parallel and perpendicular transport in MHD turbulence
Abstract

Cosmic ray (CR) transport is essential for many astrophysical problems, e.g., CMB foreground, ionization of molecular clouds and all high energy phenomena. Recent advances in MHD turbulence call for revisions in the paradigm of cosmic ray transport. We use the models of magnetohydrodynamic turbulence that were tested in numerical simulation, in which turbulence is injected at large scale and cascades to to small scales. I shall demonstrate that compressible fast modes instead of Alfven modes dominate the transport of CRs. I shall introduce a non-linear formalism that extends the ordinary Quasi-Linear Theory (QLT) that is routinely used for the purpose. This allows us to avoid the usual problem of 90 degree scattering and enable our computation of the mean free path of cosmic rays. Implications for particle transport in Solar flare and interstellar medium will be discussed. In addition, I address the issue of the transport of CRs perpendicular to the mean magnetic field and show that the issue of cosmic ray subdiffusion is only important for restricted cases when the ambient turbulence is far from that suggested by numerical simulations. As a result, this work provides a formalism that can be applied for calculating cosmic ray propagation in a wide variety of circumstances.

272008-05-02 Fri
14:00~15:00
R716
Prof. Shinsuke Abe
[NCU]
Asteroids and their fragments
Abstract

It is of great importance to know evolution of solar system small bodies. Asteroids that have survived since the early solar system (4.6 Gyr ago) have experienced numerous collisions that influenced thermal histories and orbital properties. Thus, the physical nature (size, shape, density, composition and orbital distribution) of asteroids is fundamental to understanding how our solar system has been evolved. Some asteroids are in fact either dead or dormant cometary nuclei. Though an Earth impact of 1 km-size asteroid is likely within a million years, frequent meteor fireballs or meteorite falls on Earth are indications of collision (ejection) events. Asteroidal particles have been proposed as a source of some meteor showers. However, their parent bodies and dynamical evolution of meteoroids are still subject to debate. In my talk, I'd like to present topics about asteroid Itokawa explored by Japanese spacecraft HAYABUSA, asteroidal Earth-grazing fireball and meteoroid's Lunar impact flush. (1)Japanese spacecraft 'HAYABUSA', which was launched on May 9 2003, has been developed to investigate an asteroid 'Itokawa'. The purpose of the mission is sample return from the Itokawa. As a result, its mission was featured in the scientific magazine "Science" as a first Japanese mission to illustrate various new findings. I mainly present about my works on gravity (density and porosity) and surface conditions (space weathering, morphology and cratering age). (2) A bright fireball observed from 8 stations in Japan penetrated into the atmosphere with the initial velocity of 18.85 km/s, reached a minimum height of of 71 km, and then escaped from the Earths gravity. Atmospheric ablation and fragmentation enabled us to identified the body as type-II, corresponding to carbonaceous chondrite. Precise triangulation measurements during the meteorite entry make it possible to calculate the orbit that the meteorite was following before (and after) encounter with the Earth. (3) The Lunar Impact Flush is thought to be a phenomenon after a hyper-velocity impact of a large dust particle on the Moon. On the night of 15 December 2007 during Geminid meteor shower (impacting velocity is approximately 35 km/s), the first color video images carried out using a newly developed high-sensitive CCD camera were successfully observed. I will present preliminary results about my new findings.

282008-04-25 Fri
14:00~15:00
R716
Prof. Hideo Matsuhara
[Institute of Space and Astronautical Science (JAXA)]
Deep Extragalactic Surveys with AKARI Infrared Space telescope
Abstract

AKARI is a 68.5cm cooled telescope dedicated for large-area surveys at 2.4-160 microns. Overview of the mission as well as the deep extragalactic surveys toward the ecliptic pole regions and their initial results will be presented. The observing plan in the warm mission phase starting from this May is also introduced. Finally, SPICA, the Japanese-led next generation space IR telescope mission, and the proto-type of one of the focal plane instrument are briefly described.

292008-04-11 Fri
14:00~15:00
R716
Dr. Jiwoo Nam
[NTU]
Neutrino hunting with ANITA experiment
Abstract

The ANITA (ANtarctic Impulsive Transient Antenna) is a balloon-borne neutrino telescope which consists of an array of 32 broadband horn antennas. It successfully completed a 35 day flight over Antarctica during the 2006-2007 austral summer. The primary goal of ANITA is to search for astrophysical neutrinos with energies E > 1019 eV by detecting radio Cherenkov signals from neutrino-induced showers in the Antarctic ice. We present preliminary results from ongoing analyses of ANITA data.

302008-03-28 Fri
14:00~15:00
R716
Dr. I-Hui (Tornado) Li
[Centre for Astrophysics and Supercomputing, Swinburne University, Australia]
Finding Galaxy Groups Using Photometric Redshifts
Abstract

sing a sample of 1212 galaxy groups drawn from the Red-Sequence Cluster Survey (RCS) four-band photometric-redshift catalogs, we study properties of galaxy groups at 0.2 < z < 0.6 and probe group environmental influence on galaxies therein. The galaxy groups are identified using a `probability Friends-of-Friends' (pFoF) algorithm, which is developed specific to search for galaxy groups using photometric redshifts. I will present the algorithm and its tests on mock catalogs. By applying the pFoF algorithm to the RCS sample, we find that red galaxy fractions in galaxy groups decrease with redshift and the rate has a positive correlation with group richness. This `group downsizing' effect is consistent with the group halo mass being a dominant factor in galaxy evolution. The differences among groups of different richness are most apparent in group centers.

312008-03-14 Fri
14:00~15:00
R716
Dr. Yuji Urata
[Saitama University]
Crisis of the GRB standard fire ball model
Abstract

Recently, thanks to Swift X-ray and ground based optical follow-ups, many new phenomena were found in GRB afterglow such as X-ray flare, X-ray shallow decay phase, quite different temporal evolution between X-ray and optical afterglow. These surprising observational results cannot be explained by the GRB standard fire ball model which was likely established in pre-Swift era. In this talk, I will summarize recent observational results and our effort based on EAFON and Suzaku/WAM.

322008-02-29 Fri
14:00~15:00
R716
Dr. Sujan Sengupta
[Indian Institute of Astrophysics]
Polarization - A Potential Tool to Probe Brown Dwarfs and Exoplanets
Abstract

Polarization is a measure of anisotropy in any radiation field. Polarization of light occurs either by magnetic field or by scattering. In the last decade, a major astronomical field has been emerged out - Substellar Mass Objects that include brown dwarfs and extrasolar planets or exoplanets. Due to low atmospheric temperature, the photopshere of brown dwarfs and exoplanets produces condensation of various species with size ranging from sub-micron to several tens of microns. Scattering by dust yields into detectable amount of polarization. The rotation-induced oblateness of the photosphere of brown dwarfs makes incomplete cancellation of the net polarization over the photosphric disk. Recent observation has detected non-zero linear polarization from several brown dwarfs with relatively higher effective temperature. Very recently, the first detection of linear polarization from a close in planet is reported. In addition to probe the atmospheric properties of exoplanets, polarization can be used to detect small earth like planets that cannot be detected by any other existing methods. In this talk, I shall present theoretical models that explain the observed polarization from brown dwarfs and exoplanets and discuss about how polarization can be used as a potential tool to understand the atmospheric properties of brown dwarfs and exoplanets.

332008-02-26 Tue
14:00~15:00
R716
Dr. Hiroyuki Hirashita
[University of Tsukuba, Japan]
Dust as a Key Species for Galaxy Evolution
Abstract

The galaxy evolution is one of the fundamental and unsolved problems in astrophysics. In the context of galaxy evolution, the history of metal production by stars is an important aspect in investigating the origin of the present metal-rich universe. Roughly half of metals are known to be condensed into dust grains in the local universe. In this talk, I present some of my studies that focus on the importance of dust grains in galaxy evolution. Based on our theoretical models, we show that dust grains play a crucial role in promoting star formation even in primeval (very metal-poor) galaxies. Indeed, dust grains are effective in helping to form molecules and in blocking UV-heating radiation. These two effects efficiently promote star formation and result in a significant population of dust-enshrouded galaxies even at z > 5. Those galaxies can be tackled with ALMA. I also present some efforts to understand galaxy formation and evolution from observed dust extinction and emission, mentioning some strategies for future ALMA observations of primeval galaxies.

342008-02-22 Fri
14:00~15:00
R716
Prof. Aaron Evans
[SUNY at Stony Brook]
Molecular Gas and the Host Galaxies of Quasi-Stellar Objects
Abstract

I will summarize recent work on the star-forming molecular gas properties of quasi-stellar object (QSO) hosts. This population has become of increasing importance to studies of massive galaxy evolution, primarily as a result of the apparent connection between star formation and active galaxy nuclei (AGN) activity in massive galaxies, and of the possible evolutionary connection between QSO hosts and luminous infrared galaxy mergers. Multi-wavelength observations will be folded in to give a well-rounded view of this transitory phenomenon.

352008-02-20 Wed
14:00~15:00
R716
Prof. Keiichi Wada
[]
TBA
362008-02-05 Tue
14:00~15:00
R716
Dr. Kate Su
[University of Arizona]
Debris Disks: From Stellar Nurseries to Graveyards
Abstract

Debris disks form when asteroidal-scale bodies collide or star-gazing comets evaporate presumably due to dynamical perturbations from large planet-size objects, generating fine dust through collisional cascades. Therefore, debris disks are indirect (but clear) evidence that some form of planetary system is present. Because dust grains in the disk provide a large emitting surface area, the dusty disk is the most easily observable component of planetary systems. The record of events in the planetary forming zones traced by the study of debris disks around stars at various evolutionary stages offers a great opportunity to understand how planetary systems form and evolve. I will present recent results from Spitzer observations of debris disks around main-sequence stars and white dwarfs with the ultimate goal of connecting them with theories for the evolution of our solar system.

372008-02-01 Fri
14:00~15:00
R716
Prof. Hsiao-Wen Chen
[University of Chicago]
Halo Occupation of Dark Baryons
Abstract

Observations of QSO absorption-line systems have revealed a wealth of information for the intergalactic medium from the nearby universe all the way to the epoch of reionization. These absorbers offer a powerful tool for mapping the dark universe, but their correlation with known stellar populations has always been ambiguous. I will describe on-going surveys of absorbers and galaxies along common lines of sight toward background quasars, for quantifying the cross-correlation between stars and gas. I will also introduce a new technique we have developed for constraining the baryon content of dark matter halos based on absorption-line statistics.

382008-01-29 Tue
10:30~11:30
R716
Dr. Paolo Giommi
[ASDC/ASI]
Space Programs in Italy
392008-01-17 Thu
14:00~15:00
R716
Prof. Michael S Bessell
[Research School of Astronomy and Astrophysics, the Australian National University]
The SkyMapper Telescope and the Southern Sky Survey
Abstract

In early 2008, the Research School of Astronomy and Astrophysics, ANU, will begin a multicolor, multi-epoch survey of the southern sky from Siding Spring OIbservatory. The SkyMapper telescope is a 1.3m telescope with a 5.6 square degree field of view built by EOS. Its focal plane comprises 32 2Kx4K E2V deep depletion CCDs. The limiting magnitudes will be fainter than the SDSS survey due to the improved CCDs. We aim for at least 3% precision in the u,v,g,r,i and z bands between 8th and 22 magnitude. The u and v bands (like Stromgren u and DDO 38 bands respectively) together with the g and i bands will permit detailed temperatures, gravities and metallicities to be determined for a wide variety of old-disk and halo stars while the g, i, r and z bands (similar to the SDSS bands) will provide photometric velocities and luminosities for galaxies and identify many nearby late-M, L and T dwarfs. In this talk I will decribe the telescope and associated passbands and outline some of the scientific programs that we will be undertaking and the prospects for collaboration.

402008-01-16 Wed
14:00~15:00
R716
Prof. Kristen Menou
[Columbia University]
Cosmological Physics with Black Holes
Abstract

The gravitational observatory LISA will detect coalescing pairs of massive black holes, accurately measure their luminosity distance and help identify a host galaxy or an electromagnetic counterpart. I will describe observational strategies focused on identifying such electromagnetic counterparts and associated host galaxies. Successful identifications would enable a novel type of astrophysical studies and new fundamental tests of gravitational physics on cosmological scales.

412008-01-11 Fri
14:00~15:00
R716
Dr. Rui-Qing Mao
[Purple Mountain Observatory, China]
The bar-driven spiral inflow towards the nucleus: a case study in NGC 6946
Abstract

Bars are common in spiral galaxies, and have been invoked to throw light on one of the fundamental questions in galactic evolution: how is material driven all the way in to the nuclear region participating starbursts, or feeding the supermassive black hole and AGN there. NGC 6946, a nearby late-type spiral galaxy with multiple bar structures, is an ideal laboratory for detailed study of the bar-driven mass flow mechanism under "bars-within-bars" scenario. With the unique ability of SMA that can provide a sub-arcsec resolution at submillimeter wavelengths, we are able to study its gas kinematics in a linear scale of about 20 pc. I will present our SMA results of CO(3-2), CO(2-1) and 13CO(2-1) towards the central region of NGC 6946 and discuss the detailed kinematics.

422008-01-04 Fri
14:00~15:00
R716
Dr. Wei-Hao Wang
[NRAO]
Toward a Complete Picture of the Submillimeter Galaxy Population
Abstract

The origin of the submm extragalactic background light (EBL) measured by the COBE/DIRBE experiment remains unclear. Only approximately 30% of the submm EBL has been resolved into bright submm galaxies, among which roughly 2/3 can be identified with radio interferometry. These radio identified submm sources are found to be at z=2-3 and they dominate the total star formation at this redshift. On the other hand, very little is known about the rest 80% of the EBL that is either too faint to be detected by current submm instruments or cannot be identified in the radio. Our group in Hawaii has been targeting these unknown submm EBL sources. With various direct and indirect approaches, we are able to determine the number counts of faint submm galaxies and we found that they are a low-redshift population. We also found the first evidence showing that radio-faint submm-bright sources are at high-redshift. With all these, we can start to put the submm galaxy population into the content of galaxy formation and evolution, and to prepare ourself for the next-generation instruments such as the EVLA, ALMA, and the JWST.

TEL: 886-2-3365-2200 FAX: 886-2-2367-7849
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