| Date/Time/Place |
Speaker / Topic |
Abstract |
2008-09-12
14:00-15:00
R716 |
Dr. Oscar Morata
(ASIAA)
TBA |
no abstract |
2008-08-29
14:00-15:00
R716 |
Dr. Sandor Molnar
(ASIAA)
TBA |
no abstract |
2008-08-22
14:00-15:00
R716 |
Dr. Hsien Shang
(ASIAA)
TBA |
no abstract |
2008-07-11
14:00-15:00
R716 |
Dr. Anita Richards
()
MERLIN/VLBI maser measurements of M-stars' mass loss |
no abstract |
2008-07-04
14:00-15:00
R716 |
Dr. Tzu Ching Chang
(ASIAA)
21cm Cosmology |
no abstract |
2008-06-20
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 |
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. |
2008-06-13
14:00-15:00
R716 |
Dr. Sergei A. Levshakov
(Ioffe Physico-Technical Institute, Russia)
QSO spectra in cosmological tests |
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. |
2008-06-06
14:00-15:00
R716 |
Dr. Youhei Masada
(ASIAA)
A Key Process for Magnetohydrodynamic Phenomena in Astrophysical Compact Objects |
no abstract |
2008-06-04
14:00-15:00
R716 |
Prof. Josh Barnes
(University of Hawaii)
Identikit 1: A Modeling Tool for Interacting Disk Galaxies |
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. |
2008-05-28
13:30-14:30
R716 |
Prof. Frank Shu
(UC San Diego)
The ISM of Nearby Galaxies and the Future of the SMA |
TBA |
2008-05-23
14:00-15:00
R716 |
Dr. Yoichi Ohyama
(ASIAA)
AKARI Mid-infrared Spectroscopic Views of Galaxies out to z~0.5 |
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. |
2008-05-22
14:00-15:00
R716 |
Prof. Frank Shu
(UC San Diego)
Magnetized Star Formation: Disks, Jets, and Funnel Flows |
TBA |
2008-05-16
15:30-16:30
R716 |
Prof. Ryohei Kawabe
(Nobeyama Radio Observatory)
Recent progress and future plan of Nobeyama Radio Observatory (NRO) |
no abstract |
2008-05-09
14:00-15:00
R716 |
Dr. Huirong Yan
(CITA)
Nonlinear Cosmic ray parallel and perpendicular transport in MHD turbulence |
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.
|
2008-05-02
14:00-15:00
R716 |
Prof. Shinsuke Abe
(NCU)
Asteroids and their fragments |
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 Earth’s 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. |
2008-04-25
14:00-15:00
R716 |
Prof. Hideo Matsuhara
(Institute of Space and Astronautical Science (JAXA))
Deep Extragalactic Surveys with AKARI Infrared Space telescope |
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. |
2008-04-11
14:00-15:00
R716 |
Dr. Jiwoo Nam
(NTU)
Neutrino hunting with ANITA experiment |
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. |
2008-03-28
14:00-15:00
R716 |
Dr. I-Hui (Tornado) Li
(Centre for Astrophysics and Supercomputing, Swinburne University, Australia)
Finding Galaxy Groups Using Photometric Redshifts
|
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. |
2008-03-14
14:00-15:00
R716 |
Dr. Yuji Urata
(Saitama University)
Crisis of the GRB standard fire ball model
|
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. |
2008-02-29
14:00-15:00
R716 |
Dr. Sujan Sengupta
(Indian Institute of Astrophysics)
Polarization - A Potential Tool to Probe Brown Dwarfs and Exoplanets |
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. |
2008-02-26
14:00-15:00
R716 |
Dr. Hiroyuki Hirashita
(University of Tsukuba, Japan)
Dust as a Key Species for Galaxy Evolution |
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. |
2008-02-22
14:00-15:00
R716 |
Prof. Aaron Evans
(SUNY at Stony Brook)
Molecular Gas and the Host Galaxies of Quasi-Stellar Objects |
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. |
2008-02-05
14:00-15:00
R716 |
Dr. Kate Su
(University of Arizona)
Debris Disks: From Stellar Nurseries to Graveyards |
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. |
2008-02-01
14:00-15:00
R716 |
Prof. Hsiao-Wen Chen
(University of Chicago)
Halo Occupation of Dark Baryons |
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. |
2008-01-29
10:30-11:30
R716 |
Dr. Paolo Giommi
(ASDC/ASI)
Space Programs in Italy |
no abstract |
2008-01-17
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 |
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. |
2008-01-16
14:00-15:00
R716 |
Prof. Kristen Menou
(Columbia University)
Cosmological Physics with Black Holes |
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. |
2008-01-11
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 |
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.
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