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Activity > Colloquium

Colloquium (2010)

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
12010-12-21 Tue
14:00~15:00
R1203
Dr. Mikako Matsuura
[University College London]
Origin and evolution of dust in galaxies
Abstract

Dust grains have been thought to been formed in the surrounding of dying stars, and eventually they are ejected into the interstellar medium (ISM). That concept had been developed by the studies of objects in the Milky Way. The launches of the Spitzer Space Telescope in 2003 and the Herschel Space Observatory in 2009 have opened up a new era: the exploitation of lifecycle of dust in nearby galaxies. We will present current observational understanding of life-cycle of dust in the Local Group Galaxies, and show the implications for dust in more distant galaxies.

22010-12-17 Fri
14:00~15:00
R1203
Prof. Noriyuki Kawaguchi
[NAOJ/Mizusawa VLBI Observatory]
Japanese VLBI actitivities on technical developments --- A high speed AD and a low noise MMIC amplifier
Abstract

Japanese VLBI actitivity has started since 1977. As a member of the pioneer group, I brifely reveiw the activities form a view of the engineering developmets in Japan. Also I will present recent developments on the InP technology, a high speed AD as an application of InP HBT technology and a low noise HEMT amplifier as an InP HEMT technology. These developments are important to promote future applications to sub-mm VLBI and the SKA.

32010-12-08 Wed
11:00~11:30
R1203
Prof Carl Heiles
[UC Berkeley]
*Special Seminar*
Cigars, Pancakes, and Piglets
42010-12-08 Wed
11:30~12:00
R1203
Prof. Geoffrey Bower
[UC Berkeley]
*Special Seminar*
Dynamic Radio Sky
52010-12-03 Fri
14:00~14:30
R1203
Dr. Mingzhi Wei
[UCO/Lick Observatory]
*Special Seminar*
Astronomical CCD Evaluation and Optimization
Abstract

This talk will show what CCD performances are the most impotent to the astronomy application and compare the different features of the regular CCD and the fully depleted CCD . The methods of characterization and optimization for the astronomical CCDs and some test results will be presented in this talk.

62010-11-26 Fri
14:00~15:00
R1203
Dr. Stefanie Wachter
[WISE Science Data Center]
Shells, Bubbles and Rings: Eruptive Mass Loss on the Path to Supernovae
Abstract

Massive stars play a key role in the chemical and mechanical evolution of the ISM in galaxies. These luminous stars with their strong winds and mass outflows shape their local environment, which in turn has implications for the observed evolution of type II supernova events. Despite their importance, our knowledge about the formation and evolution of massive stars is surprisingly limited. In particular, the post main sequence evolution of massive stars, when they shed most of their mass, is poorly understood. Observationally, this stage can be explored through the study of Wolf-Rayet stars (WRs), luminous blue variables (LBVs) and red supergiants. We have recently discovered a large, obscured population of these rare evolved massive stars, which is characterized by prominent circumstellar shells in 24 micron observations from the Spitzer Space Telescope. Our IR spectroscopic follow-up of the central sources of these shells has revealed several new WRs, as well as a large number of candidate LBVs that - if confirmed - would double the existing sample. I will discuss the properties of these shell sources in the context of massive star evolution. I will also present an overview of the status and scientific capabilities of the WISE mission and its potential for massive star research.

72010-11-25 Thu
14:00~14:30
R1203
Dr. Chin-Shin Chang
[MPIfR]
*Special Seminar*
The Broadband Emission Properties of Blazar Jets
Abstract

The origin of the high-energy emission of blazars is still a matter of debate. To investigate the emission mechanism of extragalactic outflows and to pin down the emission site, we constructed a broadband spectral-energy-distribution (SED) catalog from the radio to the gamma-ray band for the complete MOJAVE sample, which consists of 135 relativistically beamed AGN with well-studied parsec-scale jets. Typically, the broadband SED of blazars shows a double-humped profile. It is believed that the lower-energy hump is due to synchrotron emission from the radio jet, and the higher-energy hump is generated by inverse-Compton upscattered seed photons. Combining the results of high-resolution VLBI observations and the multiband properties of the MOJAVE sources, we want to pin down the origin of the high-energy emission in relativistic jets, and search for the correlations of VLBI and high-energy properties.

82010-11-25 Thu
14:30~15:00
R1203
Claudio Ricci
[ISDC Data Centre for Astrophysics]
*Special Seminar*
X-ray spectra of AGN
Abstract

Active Galactic Nuclei (AGN) are powered by accretion onto a supermassive black hole. In this scheme the X-ray emission of AGN is produced by the inverse Comptonization of the thermal photons produced by the accretion disk off a corona of very hot electrons. The Cosmic X-ray background (CXB) is thought to be produced by unresolved AGN, although a great, and stil unobserved, fraction of heavily obscured AGN are needed to explain its peak around 30 keV. In this talk I will discuss the current knowledges on the X-ray spectra of AGN, and present the deepest study ever performed of their average hard X-ray (17-250 keV) spectra. I will also discuss the implications of our results on the synthesis models of the CXB, and on the unification model of AGN.

92010-11-19 Fri
14:00~15:00
R1203
Prof. Nick Scoville
[Caltech]
Large Scale Structures and Galaxy Evolution in the COSMOS Survey
Abstract

The COSMOS survey is the largest high redshift galaxy evolution survey ever done -- imaging 2 square degrees with all major space-based and ground based observatories. I will describe the key data in the survey and then present recent results on large-scale structures out ot z = 2.5, the dark matter distributions and galaxy evolution with respect to environment and redshift.

102010-11-12 Fri
14:00~15:00
R1203
Prof. David Sanders
[University of Hawaii]
The Origin and Evolution of Luminous Infrared Galaxies: new results from the GOALS and S-COSMOS surveys.
Abstract

New multi-wavelength studies of a complete sample of nearby luminous infrared galaxies (LIRGs) in The Great Observatories All-sky LIRGs Survey (GOALS), confirm that strong interactions/mergers of gas-rich spirals provide the trigger for the intense infrared luminosity, and that the most luminous objects are intimately related to intense nuclear starbursts and the the rapid growth of super massive black holes. The Spitzer-COSMOS (S-COSMOS) survey of the HST-ACS 2sqdeg field was designed to extend the detailed multi-wavelength studies of LIRGs out to higher redshifts, and more generally, to provide an infrared view of galaxies for comparison with that seen in the optical. Results from S-COSMOS suggest that the deep optical surveys have indeed missed an important class of extragalactic objects ! S-COSMOS MIPS results clearly reveal a substantial population of infrared luminous galaxies which fill the optical "green valley" . These infrared selected objects appear to provide a plausible evolutionary connection between galaxies in the "blue cloud" (starburst disks) and "red sequence" (old stars/ellipticals) -- the bimodal distribution which characterizes the extragalactic population seen in the optical.

112010-11-11 Thu
14:00~15:00
R1203
Dr. Edward Tong
[CfA]
*Special Seminar*
The Submillimeter Array (SMA): Current Status and Plan
Abstract

The Submillimeter Array (SMA) is the world's pioneering radio interferometer dedicated to astronomical observations at submillimeter wavelengths. Since 2003, we have been operating 8 six-meter antennas on Mauna Kea, covering the frequency range of 200 - 700 GHz. In this presentation, the current status of the SMA, including the latest technical developments will be reported. A summary of the major science activities of the SMA will also be presented. Plans are being made for the array to position itself in the upcoming era of ALMA. The future technical plans of expansion of the SMA will also be described.

122010-10-29 Fri
11:00~12:00
R1203
Prof Shrinivas R. Kulkarni
[Caltech]
Charting the Dynamic Universe: The Palomar Transient Factory
Abstract

Only about a hundred years ago astronomers came to recognize cosmic explosive events. What was once termed as Stella Nova are now divided into two major families, novae and supernovae (with real distinct classes in each). The variables and the explosions have been interesting in their own right and contributed richly to key problems in modern astrophysics: distances to galaxies and cosmography. The area of transient and variable stars is once again undergoing a renaissance due to wide field optical surveys. The Palomar Transient Factory (PTF) was designed to explicitly to chart the transient sky with a particular focus on events which lie in the nova-supernova gap.. With its innovative two-telescope architecture it achieves both high cadence and large areal rate of coverage. PTF was commissioned during the summer of 2009. PTF is now finding an extragalactic transient every 20 minutes and a Galactic (strong) variable every 10 minutes. Spectroscopy undertaken at Keck and Palomar has allowed us: identify an emerging class of ultra-luminous supernovae, discover luminous red novae, undertake UV spectroscopy of Ia supernovae, discover supernovae powered by something other than Nickel-56, clarification of sub-classes of core collapse and thermo-nuclear explosions, map the systematics of core collapse supernovae, a trove of eclipsing binaries, AM CVns and many others.

132010-10-29 Fri
14:00~15:00
R1203
Dr. Wada
[AISAS/JAXA]
Development of cryogenic readout electronics for space infrared astronomical observations
Abstract

We have been developing low power cryogenic readout electronics for space borne far-infrared image sensors in order to draw out full performance of cold infrared telescopes, like SPICA. We have chosen a fully-depleted silicon-on-insulator (FD-SOI) CMOS process because they keep good static performance even at 4.2 K where many bulk-CMOS FETs suffer from anomalous behaviors. We have designed and fabricated several test circuits with the FD-SOI CMOS process and confirmed that an operational amplifier operates with open loop gain to be over 1000 and with power consumption to be less than 1.3 micro watts as designed. In our presentation, we will make a report on some measurement results of the test circuits, as well as a brief introduction to the space infrared astronomical observations.

142010-10-22 Fri
14:00~15:00
R1203
Dr. Yen-Ting Lin
[ASIAA/IPMU]
Statistical Properties of Radio Galaxies at z<0.3: Host Galaxies and Environment
Abstract

Extended radio galaxies (RGs) have traditionally been classified into Fanaroff-Riley (FR) I/II types, based on the ratio r of the separation between the brightest regions on either sides of the host galaxy and the total size of the radio source. In this talk I will describe a systematic investigation of the distribution of physical properties of RGs as a function of r, in order to better understand the FR I/II dichotomy. It is found that a classification solely based on r is not enough to define two distinct populations of RGs, and we suggest that the inclusion of nuclear optical emission line is needed for a better classification scheme. Having presented an improved scheme, I will discuss possible origins of different radio morphology, and comment on feedback from RGs.

152010-10-15 Fri
14:00~15:00
R1203
Dr. Rick Perley
[NRAO]
The Expanded Very Large Array
Abstract

The EVLA project is a $90M upgrade of the Very Large Array which will multiply its scientific capabilities at least tenfold. Begun in 2000, the project will be completed by the end of 2012. Key goals for the project include: Complete frequency coverage from 1 to 50 GHz with maximum instantaneous bandwidth of up to 8 GHz; all-digital fiber-optic signal transmission from the antennas to optimize stability; a wide-bandwidth full-polarization correlator which will enable extraordinarily flexible observing modes. EVLA construction continues to progress well. All 28 antennas have been upgraded to modern standards, and about half of the 228 wideband cryogenically cooled receivers are now installed. The WIDAR correlator is now completed, and 2 GHz-wide data are now available for testing purposes. In this talk I will review the status of the project and the unique observational capabilities that the EVLA can now offer via the `OSRO' and `RSRO' programs. Examples of early science which demonstrate the potential of the completed project will be shown. The EVLA's capabilities will rapidly rise over time as the WIDAR correlator is brought to its full capability. However, the scientific productivity of the array will be set to a significant degreee by our ability to record, distribute, calibrate, and image the multi-TB datasets generated by the correlator -- these are the major challenges for the future, and I will spend some time on the observatory's plans to meet them.

162010-10-01 Fri
14:00~15:00
R1203
Alfonso Trejo
[ASIAA]
Non-thermal radio sources toward the Galactic plane
172010-09-24 Fri
14:00~15:00
R1203
Dr. Anil Pandey
[Aryabhatta Research Institute of Observational Sciences]
Star formation in and around young clusters associated with HII regions
Abstract

We are pursuing multi-wavelength studies of a few star-forming regions to study the star formation scenario. The young stellar objects (YSOs) in these regions have been identified using the near/ mid-infrared colours, slitless spectroscopy and X-ray observations. The colour-magnitude diagram of the YSOs indicates that the majority of these objects have ages between 1 Myr to 5 Myr, indicating a non-coeval star formation in the clusters. There is evidence for triggered star formation at the periphery of cluster regions. I shall discuss our recent results regarding triggered star formation around young star clusters as well as IMF of these regions.

182010-09-17 Fri
14:00~15:00
R1203
Dr. David Hiriart
[San Pedro Martir Observatory]
San Pedro Martir Observatory
192010-09-16 Thu
14:00~15:00
R1203
Prof. Chris Conselice
[University of Nottingham]
The GOODS NICMOS Survey: Watching Galaxy Formation
Abstract

I will present a full analysis of the modes of galaxy formation for massive galaxies with log M > 11 at z < 3 based on data from the Hubble GOODS NICMOS Survey. I will discuss the role of major mergers, star formation, AGN feedback, and for the first time, minor mergers, in the formation of massive galaxies down to z = 0. This is possible due to using new near-infrared Hubble Space Telescope imaging from NICMOS focused on massive galaxies in the distant universe. I will further show that modes besides the above are needed to form galaxies and will argue that gas accretion from the intergalactic medium is an important method for adding mass to the most massive galaxies, and potentially a major new part of the galaxy formation process.

202010-09-10 Fri
14:00~15:00
R1203
Prof. Takeru Suzuki
[Nagoya Univ.]
Protoplanetary Disk Winds by Magnetorotational Instability : Formation of an Inner Hole and a Crucial Assist for Planet Formation
Abstract

By constructing a global model based on 3D local magnetohydrodynamical (MHD) simulations, we show that the disk wind driven by magnetorotational instability (MRI) plays a significant role in the dispersal of the gas component of proto-planetary disks. Because the mass loss time scale by the MRI-driven disk winds is proportional to the local Keplerian rotation period, a gas disk dynamically evaporates from the inner region with possibly creating a gradually expanding inner hole, while a sizable amount of the gas remains in the outer region. The disk wind is highly time-dependent with quasi-periodicity of several times Keplerian rotation period at each radius, which might be linked with observed time-variability of protostar-protoplanetary disk systems. These features persistently hold even if a dead zone exists because the disk winds are driven from the surface regions where ionizing cosmic rays and high energy photons can penetrate. Moreover, the predicted inside-out clearing significantly suppresses the infall of boulders to a central star and the Type I migration of newly formed planets with mass below ~ 5 times the Earth mass, which are favorable for the formation and survival of planets.

212010-09-03 Fri
14:00~15:00
R1203
Dr. Chiranjib Konar
[ASIAA]
RADIO GALAXIES AND THEIR DYNAMICS
Abstract

X-ray and radio observations of Radio Galaxies (RGs), which have revealed a number of interesting results, are presented. The current observational results SEEM to have changed some of the classical ideas about radio galaxies (RGs). Studying lobes in both radio and X-ray allows us to constrain the magnetic fields (hereafter `true' fields) in lobes without assumption of equipartition between particles and magnetic field, and to get some clues to the particle content of lobes. Interestingly, the recent results suggest that the `true' fields of lobes of large FRII RGs are very close to equipartition fields and there seem to be no energetically dominant protons in their lobes. The particle content and density in the outer lobes of recurrent radio galaxies have important implications to the dynamics of the inner lobes. Studying the environments of radio galaxies is also extremely important to know the dynamics of radio galaxies. For a long time it was assumed that powerful FRII radio galaxies would expand supersonically, pushing a shock through the external medium, which would require the lobes to be over-pressured. However, X-ray observations (combined with the radio ones) show that the internal lobe pressures of powerful FRII RGs seem to be often close to the external thermal pressures and not much higher than the external pressures.

222010-08-20 Fri
14:00~15:00
R1203
Dr. Patrice Theule
[University of Provence, Marseille, France]
The thermal chemical reactions in interstellar ices
232010-08-18 Wed
14:00~15:00
R1108
Ryan Keenan
[UW-Madison]
*Special Seminar*
A deep wide-field near-infrared extragalactic survey and its many applications
Abstract

For my dissertation research, I have been working with data from a near-infrared (NIR) survey of several widely separated extragalactic fields. The survey was conducted using the 2-4 meter telescope on Mauna Kea and reaches magnitude depths of 22-23 (AB system) over ~3 square degrees and 24-25 over ~0.25 degrees. I will discuss three distinct projects involving these data. In the first, we focused on bright galaxy counts in our fields combined with other surveys to probe local large-scale structure. In the second, we use galaxy counts from our fields combined with other surveys to place new limits on the total amount of NIR light that can be attributed to resolved sources. In the third project, which I am working on now, we use our NIR photometry to create a mass-selected sample for spectroscopic follow-up in order to constrain the low redshift (z ~0.2) mass and luminosity functions.

242010-08-17 Tue
14:00~15:00
R1108
Prof. Matthias Steinmetz
[Astrophysical Institute Potsdam]
Unravelling the formation history of the Milky Way in the era of mega survey
252010-08-13 Fri
14:00~15:00
R1203
Prof. Young Chol Minh
[KASI/ASIAA]
The Circumnuclear Disk (CND) of our Galactic Center: New Interpretation on Its Kinematics
Abstract

The CND is known to be a rotating torus. Using the SMA mosaic data of HCN, CN, and SiO, we suggest that main features of the CND may have been shaped by local events, such as a local explosion. The overall rotation may not be the dominant source in shaping the CND.

262010-07-30 Fri
14:00~15:00
R1203
Dr. Tapas Das
[Harish Chandra Research Institute]
On the role of black hole spin in influencing the behaviour of transonic accretion
Abstract

Owing to the strong curvature of space time sufficiently close to the black hole, matter accreting onto black hole is expected to manifest extreme behaviour just before plunging into the event horizon. Hence the investigation of the physical properties of infalling matter at the close proximity of the event horizon is of fundamental importance in relativistic and high energy astrophysics because it provides the key features of the diagnostic spectra of stellar mass and super massive black holes. In this talk, I will discuss the role of the spin of astrophysical black holes in determining the behaviour of matter extremely close to the event horizon, leading to the possibility of detecting a new spectral signature of black hole spin.

272010-07-23 Fri
14:00~15:00
R1203
Dr. Mei-Yin Chou
[ASIAA]
Chemical Fingerprinting and Chemical Analysis of Galactic Halo Substructure
Abstract

We present an investigation of the chemical abundance patterns of halo substructures using high-resolution spectroscopic measurements. In particular, we study the abundances of the alpha-like element titanium (Ti) and the s-process elements yttrium (Y) and lanthanum (La) for M giant candidates of (a) the Sagittarius (Sgr) dwarf spheroidal (dSph) + tidal tail system, (b) the Galactic Anticenter Stellar Structure (GASS), also known as the Monoceros Ring, and (c) the Triangulum-Andromeda (TriAnd) Star Cloud. As expected, the majority of the Sgr stars show peculiar abundance patterns compared to those of nominal Milky Way stars, but as a group the stars form a coherent picture of chemical enrichment of the Sgr dSph from [Fe/H] = -1.4 to solar abundance. The overall [Ti/Fe], [Y/Fe], [La/Fe] and [La/Y] patterns with [Fe/H] of the Sgr stream plus Sgr core do, for the most part, resemble those seen in the Large Magellanic Cloud (LMC) and other current Milky Way satellites, only shifted by Delta[Fe/H] ~ +0.4 from the LMC and by ~+1 dex from Milky Way dSph satellites; these relative shifts reflect the faster and/or more efficient chemical evolution of Sgr compared to the other satellites, and show that Sgr has had an enrichment history more like the LMC than the dSph satellites. We also apply "chemical fingerprinting" to the GASS/Monoceros Ring and TriAnd Star Cloud, to explore the origins of the two systems and the hypothesized connections between them. GASS has been debated either to originate from the Galactic accretion of a satellite creating a tidal stream, or as a part of the disk, dynamically induced through warping or resonances, etc. Our exploration shows that GASS is indeed made of stars from a dSph, and that it is distinct in chemistry from outer disk stars. And whereas the TriAnd Star Cloud has been assumed to come from the tidal disruption of the same accreted Milky Way satellite as the GASS/Monoceros Ring, our comparison of the abundance patterns in Monoceros and TriAnd M giants suggests that the TriAnd Star Cloud is likely an independent halo substructure unrelated to Monoceros.

282010-07-15 Thu
14:00~15:00
R1203
Prof. Matsumoto
[Seoul National University, ISAS/JAXA]
A search for the light of first stars of the universe
Abstract

It has been believed that near infrared background is promising to detect the light from the population III stars, that is, first stars of the universe, since stellar radiation redshifts to the near infrared range and pop.III stars are too fait to be detected individually. Space observations with COBE and IRTS showed there remains unknown excess isotropic emission that could be attributed to pop.III origin, however, there remains uncertainty in obtaining absolute brightness due to the ambiguity of the model of zodiacal light. Another observational study is to detect the fluctuation of the sky, since zodiacal light is very smooth. Spitzer already reported excess fluctuation at a few arcmin scale, which was attributed to pop.III origin. Following them, we tried to detect the fluctuation of the sky towards north ecliptic pole with AKARI, at 2.4, 3.2 and 4.1 um. AKARI is advantageous to Spitzer in having cold shutter and short wavelength band at 2.4 mm. Analysis was performed both for monitor field (10 arcmin scale) and wide field (2 degree scale). Excess fluctuations that can’t be explained by known sources were detected at the angles larger than 100 arcsec. Power spectra of this excess fluctuations show clear turn over at ~1,000 arcsec. Spectrum of fluctuating power is fairly blue which is similar to the Rayleigh Jeans tail. A good correlation was found between 2.4 and 3.2 um, but correlation for 4.2 um is not so significant. These results are consistent with theoretical prediction based on the biased star formation for pop.III stars which traces distribution of dark matter. Fluctuations detected by AKARI provide crucial observational evidences to study the star formation history of first stars and evolution of a large scale structure at z~10.

292010-07-09 Fri
14:00~15:00
R1203
Dr. Nicolas Pradel
[ASTRON, the Netherlands]
Compact Symmetric Object and SKA pathfinder Lofar
Abstract

Compact Symmetric Objects (CSOs) are elusive objects observed in cm wavelength VLBI. They show a very particular structure: a double, triple, or more complex symmetric shape. This kind of shape is rare for VLBI objects and CSO are supposed to be AGN whose jets are observed in the plane of the sky. This orientation makes them useful probe to test the various models of AGN. In particular, the movements of the various component of a CSO, if it can be measured, are less affected than the other AGN observed with VLBI and give accurate real movement speed. I will present a way to directly measure these movements through phase-referencing astrometry and hybrid mapping, and I will present first results of this method. I will then present the newly opened radio telescope LOFAR, as Low Frequency Array, build in northern Europe. LOFAR is a pathfinder for SKA and will explore an old but still mostly unknown part of the spectrum : the window between 10 and 250 MHz. I will present recent results and prospectives for LOFAR, mostly in regard to the study of AGN and their evolution."

302010-07-02 Fri
14:00~15:00
R1203
Dr. Jianghui Ji
[Purple Mountain Observatory]
Extrasolar planets: dynamics and formation
312010-06-30 Wed
14:00~15:00
R1203
Dr. Sheng-Cai Shi
[Purple Mountain Observatory, CAS, China]
*Special Seminar*
Development of THz Superconducting Mixers and Dome A THz Project
Abstract

With an altitude of 4093m and temperature below -80 Celsius degree, Dome A in Antarctic is a very promising site for THz observations, especially at frequencies beyond 1THz. The construction of China’s Antarctic Kunlun Station at Dome A offers an unprecedented opportunity to the construction of astronomical facilities there. Purple Mountain Observatory is proposing to construct a 5-m THz telescope at Dome A. This talk will address our latest developement of THz superconducting mixers and the Dome A THz project.

322010-06-24 Thu
14:00~15:00
R1203
Prof. Howard Yee
[University of Toronto]
How to Write Winning proposals and Good Scientific Papers
332010-06-18 Fri
14:00~14:30
R1203
Prof. Chien-Chang Yen
[FJU]
Hydrogen hydrodynamic escape from planetary atmospheres
Abstract

Hydrogen is likely to be abundant in palao Earth atmosphere and is the major component in giant planets. The planetary atmospheric chemical composition is affected by planetary escape. The escape of a hydrogen-rich planetary atmosphere heated by the radiation of its parent star is under investigation using a modified version of the Antares code in the one dimensional spherically symmetric approximation. In contrast to previous versions of the code, the time dependent hydrodynamic equations are solved with allowance for energy sources and sinks associated with irradiation and thermal heat conduction respectively. The models were evolved to a steady state and transonic solutions were obtained. These studies will allow one to place constraints on the structure and evolution of the atmosphere as a function of time. Comparisons with measurements obtained from instruments aboard spacecraft of objects within the solar system will allow one to determine the properties of the atmosphere of the planetary objects when formed.

342010-06-18 Fri
14:30~15:00
R1203
I-Chun Tsai
[NTU]
Aerosol formation in the atmospheres of Titan and Venus
Abstract

Aerosols are known to be present in abundance in the atmospheres of Titan[1] and Venus[2]. However, their formation mechanism and chemical properties remain poorly known. In this study, a detail microphysical model[3] is used to analyze the possible nucleation and condensation processes occurred in Titan and Venus’s atmospheres. Sensitivity for the most probable unary and binary nucleation pathways and the subsequent condensation growth of particles is performed based on observed chemical and thermodynamic conditions of Titan and Venus’s atmosphere. The model is first validated using a laboratory simulation[4]. Comparing to laboratory results, our model simulation shows that binary nucleation from CH4 and N2 produces reasonable particle number concentration as in Titan’s atmosphere when appropriate accommodation coefficient for vapor condensation is applied. Results of sensitivity tests shown that the inject temperature, time scale of mixing and conduction and surface tension are significant uncertainties in this simulation. In Venus’s atmosphere, binary nucleation from water and sulfuric acid vapors is sufficient to produce the observed values. These results could provide not only information of the size and composition of particles in Titan and Venus’s atmosphere but also help to design laboratory experiments for measuring critical thermodynamic parameters relevant to the particle production mechanisms, as well as for interpreting observations. Referenecs: [1] McKay et al., 2009, Planetary and Space Science, doi:10.1016/j.pss.2009.08.008 [2] Titov, D. V. et al., 2009, Solar System Research, 43, No. 3, pp. 185–209. [3] Chen, J-.P. et al., 1994, J. Atmos. Sci., 51, 2613-2630 [4] Wang et al., 2010, accepted by Icarus.

352010-06-11 Fri
14:00~15:00
R1203
Prof. Pisin Chen
[NTU]
The Dark Energy Puzzle
362010-06-04 Fri
14:00~15:00
R1203
Prof. Howard Yee
[University of Toronto]
Recent Results on Galaxy Evolution and Cosmology from the RCS and the SpARCS Surveys
Abstract

The Red-Sequence Cluster Surveys (RCS1 and 2) and the Spitzer Adaptation of RCS (SpARCS) survey are large-area, multi-color imaging surveys designed to construct large cluster catalogs out to z~1.5. I will give a brief summary of the surveys and present some recent results on galaxy group and cluster evolution and gravitational lensing from these surveys. From the RCS1 I will present the investigation of the galaxy population and its evolution of a sample of ~1000 galaxy groups at 0.21 clusters from the SpARCS cluster catalog.

372010-06-03 Thu
14:00~15:00
R1203
Prof Hagai Netzer
[Tel Aviv University]
*Special Seminar*
Co-evolution of active and star-forming galaxies from z=2 to z=0
382010-06-01 Tue
14:00~15:00
R1203
Dr. Masanori Nakamura
[JHU/STScI]
*Special Seminar*
Magnetohydrodynamic Properties of Extragalactic Jets
Abstract

Some of the unanswered fundamental questions about extragalactic jets include the location where the flow becomes relativistic and where acceleration and collimation terminate, as well as the specifics of how the flow interacts with the ISM. The theory that magnetic fields are instrumental in the formation and propagation of jets in active galactic nuclei dates back four decades. Despite a recent growing consensus on this notion stemming from the results of numerical simulations of magnetohydrodynamic (MHD) flows near black holes, the precise dynamical role of magnetic fields in observed parsec and kiloparsec jets remains uncertain. Such observed properties as superluminal motions, wiggled structures, and lobe/bubble formation are discussed based on numerical simulations to constitute the foundation of an MHD paradigm for extragalactic jets

392010-05-28 Fri
16:00~16:30
R1203
Dr. Tomonori Usuda
[NAOJ]
Subaru Telescope Instruments: Path to TMT
402010-05-28 Fri
16:30~17:00
R1203
Dr. Nobunari Kashikawa
[NAOJ]
TMT Instumentation & Science Cases
412010-05-21 Fri
14:00~15:00
R1203
Prof. Aaron Evans
[UVA/NRAO]
The Great Observatories All-sky LIRG Survey (GOALS): A Mid-2010 Update
422010-05-14 Fri
14:00~15:00
R1203
Shiang-Yu Wang
[ASIAA]
The TAOS 2 Camera and OIR Detector Development in IAA
432010-05-04 Tue
14:00~15:00
R1203
Prof. Tohru Nagao
[Ehime University, Japan]
*Special Seminar*
Metallicity Evolution of Active Galactic Nuclei
Abstract

Chemical evolution of galaxies is an exciting topic in the modern extragalactic astronomy since it would give unique constraints on galaxy evolutionary models. One serious problem in the observational study on the galaxy metallicity evolution is that the target redshift range is currently limited only at z<3, due to observational limitations. On the other hand, the metallicity of AGNs are rather easily observable even at much higher redshifts, thanks to their huge luminosities and various rest-UV metallic emission lines. The AGN metallicity is interesting also because it would possibly give us crucial keys to reveal the galaxy-BH "coevolution". In this seminar, I will briefly introduce myself and my institute, and then report our recent observational studies on the AGN metallicity and its redshift evolution. Finally I will mention on our future project "Subaru Wide-Field AGN Survey (SWANS)" using the coming Subaru instrument, Hyper Suprime-Cam.

442010-04-29 Thu
14:00~15:00
R1203
Dr. Sean Andrews
[CfA]
Planet-forming Disks Around Young Stars
Abstract

Direct observations of the reservoirs of planet-building material - the disks around young stars - play a critical role in developing theoretical models of the planet formation process. I will present state-of-the-art high angular resolution Submillimeter Array (SMA) observations designed to provide new insight into the spatial distribution of mass in young protoplanetary disks. Based on these SMA data and a suite of ground- and spaced-based observations, we have developed a radiative transfer modeling toolkit that can be used to derive the temperature and density structures for a given disk. The results are being used to characterize some of the key disk evolution processes and to estimate the likelihood of future planet formation in these systems. In fact, a growing sample of disks exhibit compelling evidence that the planet formation process has gotten a head start. I will highlight some exciting new observations that resolve low-density disk cavities on Solar System size-scales and discuss how these may prove to be the signposts of very young (1 Myr) planetary systems. Along the way, I will comment on how this work foreshadows what we expect from next-generation instruments in this field, in particular from the ALMA starting in 2012.

452010-04-14 Wed
15:30~16:30
R1203
Dr. Yoshito Shimajiri
[Nobeyama Radio Observatory]
*Special Seminar*
Survey for Possible External Triggers of Star Formation in the Orion A Molecular Cloud
Abstract

We present wide and deep images with AzTEC mounted on ASTE in the 1.1 mm continuum and with BEARS on NRO 45 m in the 12CO (1--0) emissions toward the Orion A GMC. With these data, we have investigated the detailed structure and kinematics of gas associated with the Orion A GMC and has found several pieces of evidence for the external triggers for star formation. From our search, four types of the possible triggers have been revealed. Our extensive wide-field and high-sensitivity imaging has first revealed the possible external triggers of star formation in the Orion A GMC.

462010-04-13 Tue
14:00~15:00
R1203
Dr. Sherry Suyu
[Uni-Bonn]
Exploring the Dark Universe with Gravitational Lensing
Abstract

Strong gravitational lens systems provide a tool for measuring cosmological parameters and for probing galaxy mass distributions. In the first part of my talk, I will show how strong lens systems with measured time delays between the multiple images can be used to measure the "time-delay distance" to the lens, and thus the Hubble constant. In particular, I will present a Bayesian analysis of the strong gravitational lens system B1608+656, incorporating (i) new, deep HST observations, (ii) a new velocity dispersion measurement of the primary lens galaxy, (iii) an updated study of the lens environment, and (iv) time delay measurements. Our analysis of the HST images takes into account the extended source intensity distribution, and the dust extinction and optical emission by the interacting lens galaxies. By modeling the primary lens galaxy stellar dynamics and the density environment of the lens, we break the mass-sheet degeneracy present in the lensing analysis and measure cosmological parameters through the time-delay distance. I will present the resulting constraints on cosmological parameters, particularly the Hubble constant and the dark energy equation of state, from the combination of B1608+656 and the Wilkinson Microwave Anisotropy Probe data. In the second part of my talk, I will focus on using gravitational lensing to probe the properties of the dark matter haloes of galaxies, independent of their light profiles. In particular, I will present a measurement of the dark matter halo size of the satellite galaxy in the massive elliptical lens SL2SJ08544-0121.

472010-04-09 Fri
14:00~15:00
R1203
Dr. Pavlos Protopapas
[CfA]
Automatic classification of variable stars using machine learning techniques
482010-04-01 Thu
14:00~15:00
R1203
Fred Walter
[Stony Brook]
Novae!
Abstract

Novae, thermonuclear detonations on the surfaces of white dwarfs in close binary systems, are the third largest explosions in the universe. Novae are important because they enrich the ISM with low-z elements and because they may be a progenitor of the type Ia supernovae. I will provide an overview of the nova phenomenon, illustrated with results from 6 years of spectro-photometric monitoring of some 45 galactic novae with the SMARTS facilities at Cerro Tololo, Chile. The combination of ground-based observations with X-ray observations from Swift is providing powerful tools to investigate the super-soft phase of steady nuclear burning in these system. Multiwavelength high cadence observations are making it clear that the novae are far more complex that we had thought. I will concentrate on observations of the recent recurrent novae YY Dor, N LMC 2009, KT Eri, and U Sco. The line profiles and their temporal decay suggest that the accretion disk survives the nova explosion, at least in the recurrent novae.

492010-03-31 Wed
14:00~15:00
R1203
Dr. Stephane Claude
[HIA]
HIA Millimetre Instrumentation Laboratory
Abstract

I will give a brief description of the Hertzberg Institute of Astrophysics Instrumentation work and then present the current activities of the Millimeter Instrumentation Laboratory. This includes ALMA and SKA development programs.

502010-03-30 Tue
14:00~15:00
R1203
Dr. Yosuke Mizuno
[UA Huntsville]
Stability of Magnetized Relativistic Jets
Abstract

Relativistic jets have been observed or postulated in various astrophysical sources, including active galactic nuclei (AGNs), microquasars in the galaxy and gamma-ray bursts (GRBs). There are four major problems related to the relativistic jets: 1. formation mechanism, 2. acceleration mechanism, 3. collimation mechanism, and 4. long-term stability. The most promising mechanisms for producing and accelerating relativistic jets, and maintaining collimated structure of relativistic jets involve magnetohydrodynamical processes. We investigated the stability of magnetized relativistic jets via 3D Relativistic MHD simulations. First we investigated the stability of magnetized spine-sheath [UTF-8?](two component) relativistic jets against Kelvin-Helmholtz (KH) instability. We found that destructive KH modes can be stabilized even when the jet Lorentz factor significantly exceeds the Alfven Lorentz factor. Even in the absence of stabilization, spatial growth of destructive KH modes can be reduced by the presence of mildly relativistic sheath flow around a relativistic jet spine. Second we studied the temporal development of current-driven (CD) kink instability in magnetically dominated relativistic jets. In this investigation a static force-free equilibrium helical magnetic configuration is considered in order to study the influence of the initial configuration on the linear and nonlinear evolution of the instability. We found that the initial configuration is strongly distorted but not disrupted by the CD kink instability. The linear growth and nonlinear evolution of the CD kink instability depends moderately on the radial density profile and strongly on the magnetic pitch profile. We also present preliminary results showing the effect of velocity shear on the spatial and temporal development of the CD kink instability.

512010-03-26 Fri
14:00~15:00
R1203
Prof. You-Hua Chu
[UIUC]
How to Give a Good Talk
522010-03-24 Wed
14:00~15:00
R1203
Dr. Ciska Kemper
[Univ. of Manchester]
Written in stone: Dust formation in the universe
Abstract

In the Milky Way and many other galaxies, baryonic matter follows a continuous cycle: Stars form in dense clouds in the interstellar medium and at the end of their lifes, these stars return a significant amount of material to the interstellar medium. Not only do these stellar ejecta thus enrich the interstellar medium with metals, in many cases they also provide suitable circumstances for dust formation, contributing to the interstellar dust reservoir. I will introduce the field of astromineralogy by discussing the physical processes that govern dust formation and determine its composition and other properties. I will also give an overview of sources of dust, including, but not limited to, stellar ejecta. The talk will be concluded with an overview of future directions in astromineralogy and its importance to astrophysics.

532010-03-16 Tue
14:00~15:00
R1203
Dr. Elizabeth McGrath
[UCSC]
Massive Quiescent Galaxies in the Early Universe
Abstract

Fossil studies of massive elliptical galaxies suggest the majority of their stars were formed over a very short period of time early in the history of the universe, however the mechanism by which they assemble their stars remains highly debated. I will present results from a multi-wavelength study of several galaxies at z~1.5 which may be the direct progenitors of the massive galaxy population at lower redshifts. These galaxies have baryonic masses >10^11 Msun and stellar populations that already appear to be >1 Gyr old at z~1.5. Rest-frame near-UV spectroscopy indicates that these galaxies are remarkably quiescent, with any current star formation constrained to be <1 Msun/ yr. Furthermore, using Spitzer IRAC data, I will show how we are able to break the age-metallicity degeneracy that plagues shorter wavelength observations in order to eliminate much of the remaining uncertainty as to the nature of the stellar populations in these galaxies. I will use these improved age estimates in conjunction with high-resolution morphological data from HST to place these galaxies in context with current models of galaxy formation. Unlike their descendants in the local universe, we find a range in size and morphology, including extremely compact spheroids as well as massive disks of old stars. Very few of these galaxies resemble the typical spheroids that dominate galaxies comprising old stellar populations at the present epoch, indicating that several different mechanisms could be important in building up the most massive galaxies in the universe.

542010-03-12 Fri
14:00~15:00
R1203
Dr. Dalibor Kocevski
[UCSC]
Starburst Activity in High Redshift Galaxy Clusters
Abstract

I have used Spitzer 24um imaging and extensive Keck spectroscopy to identify and study the obscured starburst population within six clusters and groups at z~0.9. I will show that the density of 24um-bright galaxies in the cluster environment is nearly twice that of the surrounding field at this redshift and that this overdensity scales with the cluster's dynamical state. These galaxies often appear optically unremarkable and exhibit only moderate [OII] line emission due to severe obscuration. Their spatial distribution suggests they are an infalling population, but a close examination of their star formation histories, morphologies and optical colors indicate they are not simply analogs of the field population that have yet to be quenched. We find they have significantly redder optical colors, higher levels of extinction and that their optical spectral show an excess of Balmer absorption that is not observed in field galaxies with equivalent infrared luminosities. My modeling suggests a greater fraction of 24um-bright galaxies in denser environments are experiencing a burst of star formation in the early Universe compared to their counterparts in the field at the same redshift. Using HST / ACS imaging I also find that disturbed morphologies are prevalent among the starburst population, indicating galaxy interactions may play a role in triggering this increased activity. I will discuss the ramifications of these findings in light of recent reports that the star formation-density relationship may be reversed at z~1.

552010-03-11 Thu
14:00~15:00
R1203
Dr. Sebastien Muller
[Onsala Space Observatory]
Molecular absorption in galaxies at intermediate redshifts
Abstract

Absorption line studies in front of bright background quasars offer an unique opportunity to detect rare molecular species in distant galaxies. A score of molecular species have been observed so far in 4 objects, some of which through several rare isotopologues. The isotopic ratios of C, N, O and S have notably been measured in two galaxies at z=0.89 and z=0.68, showing significant differences with corresponding ratios in the local Universe and revealing the youth of the gas. In addition, the time variability of absorption lines toward the quasar PKS1830-211, with the near disappearance and resurrection of an absorption component within a few year time scale, gives the chance to directly measure the size of molecular clouds at z=0.89. I will present new results from a spectral survey toward PKS1830-211 and mention the use of these molecular absorption lines to constrain variations of fundamental constants, such as the proton-to-electron mass ratio, over cosmological scales, and measurement of the cosmic microwave background temperature at different redshifts.

562010-03-10 Wed
14:00~15:00
R1203
Prof. Boonrucksar Soonthornthum
[NARIT]
Progress Report of National Astronomical Research Institute of Thailand: Vision, Strategic and Action Plans
572010-03-05 Fri
14:00~15:00
R1203
Prof. Maurice HPM van Putten
[Universite d'Orleans]
Multi-messenger emissions from Kerr black holes
Abstract

Kerr black holes appear to be ubiquitous in the Universe, in active galactic nuclei (AGN) and as remnants of massive stars. They are similar to spinning tops surrounded by frame dragging. We model their multi-messenger output in high and low energy nonthermal radiation. For supermassive black holes, results point to UHECRs from Seyfert galaxies, tentatively identified by the Pierre Auger Observatory. For stellar mass black holes, results are compared with data from BATSE, HETE II and Swift. We conclude that long GRBs are spin powered, not accretion powered. We identify GRB060614 (with no supernova) with a naked inner engine produced in the merger of a neutron star with another neutron star or with a rapidly rotating companion black hole. I predict two entirely new transients in multi-messenger surveys by LIGO-Virgo, LOFAR and ALMA: gravitational-wave bursts with negative chirps and radio bursts from GRB060614 type events, whose durations can extend to tens of seconds.

582010-03-02 Tue
10:00~11:00
R1203
Prof. Takuya Yamashita
[NAOJ]
Spectroscopy of atmospheres of exo-terrestrial planets with TMT
Abstract

"Transits and 2ry Eclipses" of exo-planets are powerful tool to study their characteristics, although their orbits should cross photosphere of their parent stars. They readily provide us with their radius, and more importantly with informations of atmospheres by spectroscopic observations. Currently, atmospheres of Hot Jupiters are studied with Spitzer and HST. Future telescopes such as JWST, SPICA and TMT may enable transit observations of exo-terrestrial planets within habitable zones. I introduce our study for future transit observations of putative exo-terrestrial planets with a high resolution spectrograph of TMT. Biomarkers, such as O2 and CH4 and warming gas (CO2) may barely be detected if very favorable transiting terrestrial exo-planets around late M stars will be found.

592010-03-01 Mon
14:00~15:00
R1203
Dr. Chien Y. Peng
[HIA]
The Coevolution of Supermassive Black Holes and Galaxies since z~4
Abstract

The discoveries of strong correlations between supermassive black hole and galaxy properties have greatly shaped our view that galaxy evolution and black hole activity are closely related. Using gravitational lenses and direct imaging methods, we are making important strides toward quantifying the black hole (MBH) vs. galaxy bulge mass (Mbulge) relation out to redshifts of ~4, and down to MBH~106 Msol in nearby galaxies. I will discuss our finding that the MBH-to-Mbulge ratio (at MBH > 108 Msol) increases at high redshifts. I will also discuss why selection biases do not weaken the conclusions. Another key evidence is that the sizes of the quasar host galaxies are highly compact compared to their mass -- a result which remarkably agrees with more recent studies of massive normal galaxies at the same epoch. Then, I will change gears to illustrate how galaxy merging can statistically produce salient features of the MBH vs. Mbulge relation virtually regardless of the initial conditions. An interesting prediction from models is that galaxies which have undergone more major mergers in the past preferentially lie on the tighter and more linear part of the MBH vs. Mtotal (total galaxy mass) relation. If, as widely believed, such merger histories tend to produce massive bulges, then statistics reveal that the more fundamental relation is actually that between the MBH and Mtotal, of which the tighter MBH-MBulge correlation is a special case. I compare predictions of statistical merging with measurements made through detailed analysis of nearby galaxies and AGNs. Taken together, these data indicate that the correlation between MBH vs. Mbulge deviates from linearity at low masses and that massive galaxies may have to grow by factors of 2-4 since redshift of 2-4.

602010-02-26 Fri
14:00~14:30
R1203
Mr. Bunyo Hatsukade
[Tokyo University]
AzTEC/ASTE 1.1 mm Deep Surveys: Number Counts and Clustering of Millimeter-bright Galaxies
Abstract

We present results of 1.1 mm deep surveys with the AzTEC camera mounted on the Atacama Submillimeter Telescope Experiment (ASTE). We surveyed the AKARI Deep Field South (ADF-S), the Subaru/XMM Newton Deep Field (SXDF), and the SSA22 fields with an area of ~1000 arcmin^2 each with an rms noise level of ~0.4-1.0 mJy. Number counts are created which probe fainter flux densities (down to 1 mJy) compared to previous surveys. The contribution of 1.1 mm sources (with >1 mJy) to the cosmic infrared background (CIB) at 1.1 mm is estimated to be 11-15%. We found The cosmic star formation rate density contributed by 1.1 mm sources (with > 1 mJy) is lower by about a factor of 5-10 compared to those derived from UV/optically-selected galaxies. Clustering analyses of AzTEC sources in the ADF-S and the SXDF found that bright (>3 mJy) AzTEC sources are more strongly clustered than faint (<3 mJy) AzTEC sources and the average mass of dark halos hosting bright AzTEC sources was calculated to be 10^ 13-10^14 Msun. Comparison of correlation lengths of AzTEC sources with other populations and with a bias evolution model suggests that dark halos hosting bright AzTEC sources evolve into systems of clusters at present universe and the AzTEC sources residing the dark halos evolve into massive elliptical galaxies located in the center of clusters.

612010-02-26 Fri
14:30~15:00
R1203
Mr. Soh Ikarashi
[Tokyo University]
An AzTEC on ASTE detection of an ultra bright Submillimeter galaxy in Subaru/XMM-Newton Deep Field and follow up observations using SMA and CARMA
Abstract

We detected an extremely bright submillimeter galaxy (SMG), AzTEC/ASTE- SXDF1100.001 (hereafter SXDF1100.001), discovered in 1100 μm observations of Subaru/XMM-Newton Deep Field using the bolometer camera AzTEC mounted on the submillimeter telescope ASTE. Subsequent CARMA 1300 μm and SMA 880 μm observations successfully confirm the AzTEC/ASTE detection. This is one of the brightest SMGs known to date; its flux density is 33.9 ± 0.78 mJy at 1100 μm and 78 ± 2 mJy at 880 μm. Multi-wavelengths counterparts are identified at the CARMA/SMA position from deep optical (Subaru), near-infrared (UKIRT), mid infrared (Spitzer), and radio (VLA 20 cm) images. We also find no significant evidence for a strong gravitational lensing toward SXDF1100.001 in the Subaru images . These results indicate that SXDF1100.001 is an intrinsically ultra bright SMG with an intrinsic far-infrared (FIR) luminosity of (5.7-62) × 10^12 Lo or SFR of 10^3− 10^4 Mo yr^-1 if we assume the dust temperature of Td = 20-40 K. The SED of SXDF1100.001 suggests a redshift of at least about > 1.4. We find that 880 μm SMA image can be modeled by two components, i.e., a spatially unresolved (< 0”.6 FWHM) peak and an extended component. About the half of the total 880 μm flux is originated from the compact component. The star formation properties of the unresolved core is similar to that of local ULIRGs' cores.

622010-02-11 Thu
14:00~15:00
R1203
Prof. Amy Barger
[U. Wisconsin (Madison)]
The Cosmic Evolution of Active Galactic Nuclei
Abstract

The Chandra X-ray satellite detects X-rays emitted during accretion onto supermassive black holes, even when they are highly obscured. Using extensive follow-up observations of the X-ray sources detected in both deep and wide-area Chandra surveys, I will describe the cosmic evolution of the X-ray luminosity functions and the reconstruction of the accretion history of supermassive black holes.

632010-02-05 Fri
14:00~15:00
R1203
Dr. Kengo Tachihara
[NAOJ]
Origin of the Interstellar Turbulence and Its Role in Star Formation
642010-02-02 Tue
14:00~15:00
R1203
Dr. Masanori Nakamura
[JHU/STScI]
Magnetohydrodynamic Properties of Extragalactic Jets
Abstract

Some of the unanswered fundamental questions about extragalactic jets include the location where the flow becomes relativistic and where acceleration and collimation terminate, as well as the specifics of how the flow interacts with the ISM. The theory that magnetic fields are instrumental in the formation and propagation of jets in active galactic nuclei dates back four decades. Despite a recent growing consensus on this notion stemming from the results of numerical simulations of magnetohydrodynamic (MHD) flows near black holes, the precise dynamical role of magnetic fields in observed parsec and kiloparsec jets remains uncertain. Such observed properties as superluminal motions, wiggled structures, and lobe/bubble formation are discussed based on numerical simulations to constitute the foundation of an MHD paradigm for extragalactic jets

652010-01-29 Fri
14:00~15:00
R1203
Dr. Chulmoon Yoo
[Asia Pacific Center for Theoretical Physics]
Gravitational Lensing in a Clumpy Universe--Magnification Probability Distribution Functions of Standard Candles in a Clumpy Univers
Abstract

Lensing effects on light rays from point light sources, such like Type Ia supernovae, are simulated in a clumpy universe model. In our universe model, it is assumed that all matter in the universe takes the form of randomly distributed objects each of which has finite size and is transparent for light rays. Monte-Carlo simulations are performed for several lens models, and we compute probability distribution functions of magnification. In the case of the lens models that have a smooth density profile or the same degree of density concentration as the spherical NFW (Navarro-Frenk-White) lens model at the center, the so- called gamma distributions fit well the magnification probability distribution functions if the size of lenses is sufficiently larger than the Einstein radius. In contrast, the gamma distributions do not fit the magnification probability distribution functions in the case of the SIS (Singular Isothermal Sphere) lens model. We find, by using the power law cusp model, that the magnification probability distribution function is fitted well using the gamma distribution only when the slope of the central density profile is not very steep. These results suggest that we may obtain information about the slope of the central density profiles of dark matter halo from the lensing effect of Type Ia supernovae.

662010-01-20 Wed
15:30~16:30
R1203
Dr. Yoshihiro Yamazaki
[Waseda University]
Scaling Properties of Growing Rough Interfaces - Its Application to CMB data from WMAP
672010-01-19 Tue
14:00~15:00
R1203
Dr. Kimitake Hayasaki
[Hokkaido University]
A new approach for probing a massive binary black hole
Abstract

Supermassive black holes in galactic nuclei are considered to have coevolved with their host galaxies. Since galaxies are well-known to evolve through frequent mergers, this strongly suggests that black hole growth is mainly caused by galaxy mergers and subsequent accretion of gas. If so, a supermassive binary black hole (BBH) with a sub-parsec scale separation is inevitably formed before the black holes merge by emitting gravitational radiation. However, there is yet no definitive observational evidence for a supermassive BBH. Here we report simulations of accretion flows around a supermassive BBH and propose a basic methodology for exploring them. In the simulations we consider a triple-disk system composing of a disk around each black hole and a circumbinary disk surrounding the two. When a supermassive BBH is in an eccentric orbit, the mass transfer from the circumbinary disk is shown to be periodic. We confirm the formation of a nonaxisymmetric accretion disk around each black hole. The light variations from these disks are significantly wavelength- dependent. While the UV and X-ray light curves exhibit significant periodic variations, the optical and IR light curves show little variation with orbital phase. Such a characteristic is unique to supermassive BBHs with a triple disk and thus provide a potential observational signature. The BBHs found in this way could be also electromagnetic counterparts of the sources of the gravitational wave. We briefly show the plan to detect massive BBH candidates with Monitor of All Sky X-ray Image and Laser Interferometer Space Antenna.

TEL: 886-2-3365-2200 FAX: 886-2-2367-7849
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11F of AS/NTU Astronomy-Mathematics Building, No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan, R.O.C.