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Activity > Colloquium

Colloquium (2011)

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
12011-12-16 Fri
14:00~15:00
R1203
Dr. Ronny Zhao-Geisler
[NTNU]
download PDF What can infrared Interferometry tell us about an AGB Star?
Abstract

Asymptotic Giant Branch (AGB) stars are the main distributors of dust into the interstellar medium. The wind of these stars is driven by strong stellar pulsation in combination with radiation pressure on dust. High-resolution mid-IR interferometry is sensitive to the structure of the stellar atmosphere and the properties of the dust shell. I will give a short introduction to AGB stars and the interferometric measurement principle, and will present the results obtained for four oxygen-rich AGB stars observed over the course of more than two years. The measured angular diameters in the mid-IR of these stars appear to be about two times larger than their photospheric diameters. The overall larger diameter originates from a warm molecular layer of water, and a detected gradual increase throughout the mid-IR can be attributed to a contribution of a spatially resolved close alumina dust shell.

22011-12-09 Fri
14:00~15:00
R1203
ASIAA-SHAO
[workshop]
32011-12-02 Fri
14:00~15:00
R1203
Dr. Takaya Nozawa
[IPMU]
download PDF Dust Production by Various Types of Supernovae
Abstract

Supernovae (SNe) have been thought to be major sources of interstellar dust. I will introduce a series of our works on dust formation in the ejecta of SNe and dust destruction by the shocks penetrating into SN remnants. I demonstrate how the mass of dust ejected from SNe to the interstellar medium depend on the types of SNe, showing that envelope-stripped SNe such as Type IIb/Ib/Ia are likely to be minor sources of dust.. I also mention the difference in estimates of dust mass formed in SNe between theory and observation, and describe that this difference is now getting resolved by the recent far-infrared observations of nearby SN remnants.

42011-11-25 Fri
14:00~15:00
R1203
Prof. Tetsuya Nagata
[Kyoto University]
download PDF Cepheid variables and star formation in the Galactic center from IRSF observations at SAAO
Abstract

I will present near-infrared observations of the Galactic center region with our Infrared Survey Facility (IRSF) 1.4-m telescope at South African Astronomical Observatory. From the observations, we recently found three classical Cepheids in the nuclear bulge with pulsation periods of approximately 20 days, within 40 parsecs (projected distance) of the super massive black hole at the Galactic center. No Cepheids with longer or shorter periods were found. We infer that there was a period about 25 Myr ago, and possibly lasting until recently, in which star formation increased relative to the period of 30-70 Myr ago. The timescale of such episodic star formation might be comparable with that of the cyclic gas accumulation predicted for the central part of the Milky Way.

52011-11-18 Fri
14:00~15:00
R1203
Prof. Shude Mao
[NAOC/University of Manchester]
download PDF Strong gravitational lensing by galaxies
Abstract

I will review the basic concepts of strong gravitational lensing by galaxies. I will mainly focus on the current status of its applications on substructures within the lens galaxies and those along the line of sight. I will also briefly mention some other potential applications including the discovery of multiple black holes using gravitational lensing and finish with a brief look into the future.

62011-11-16 Wed
14:00~15:00
R1203
Dr. Jason Rhode
[NASA JPL]
*Special Seminar*
download PDF WFIRST and Euclid
Abstract

The past decade has seen tremendous progress in astronomy that has brought us to the brink of being able to answer two very fundamental questions: What is the Universe made of? Are we alone? The first question can only be answered by trying to understand the mysterious “dark energy” causing the accelerated expansion of the Universe. This dark energy, the dominant constituent of the Universe, has a number of possible theoretical explanations, ranging from a cosmological constant, to possible modifications to Einstein’s General Theory of Relativity. The second question is motivated by the increasing frequency of detections of exoplanets and can be explored by seeking out the frequency of Earth-like planets in the habitable zone of stars similar to the sun. Both of these science goals can be best explored with a space-based wide-field telescope capable of imaging and spectroscopy. Such a platform, operating in optical to near infrared wavelengths would also make great strides in a myriad of ancillary astrophysical areas, including the evolution of galaxies and structures over two thirds of the age of the Universe. The European Space Agency is in the final stages of examining the Euclid mission, which is optimized to study dark matter and dark energy. NASA has begun planning for the Wide Field Infrared Survey Telescope designed to explore dark energy and perform an exoplanet survey. I’ll discuss the scientific motivations of both missions and give an overview of the hardware, observing strategy and status of each mission.

72011-11-10 Thu
14:00~15:00
R1203
Prof. Thomas Henning
[MPIA]
The Earliest Stages of Massive Star Formation From Spitzer to Herschel
Abstract

The talk will discuss progress in our understanding of the earliest stages of massive star formation . The ISO and Spitzer infrared space missions revealed a new class of astronomical objects, the Infrared Dark Clouds (IRDCs). These very cold and dense molecular clouds are potential sites of massive star formation. Their properties will be discussed in the talk. With the successful operation of the Herschel observatory we are now in the position to search for massive pre-stellar cores in the IRDCs. The discovery of the first examples for such objects will be highlighted in the talk.

82011-11-08 Tue
14:20~15:20
Physics Building R104
Prof. Thomas Henning
[MPIA]
*ASIAA/NTU Joint Colloquium*
Physics of Star Formation
Abstract

Star formation is a fundamental process in the universe, shaping the structure of our and other galaxies. The talk will summarize the general principles of the star formation process. It will discuss global properties such as the star formation efficiency and the initial mass function. In addition, it will also demonstrate the power of adaptive optics in revealing the structure of star-forming regions.

92011-11-04 Fri
14:00~15:00
R1203
Dr. Mike Cai
[UCSD]
Fight Against Climate Change – making artificial coal
Abstract

I will review the recent developments on the torrefaction project. By using a revolutionary technology, we are able to reduce the coal making process from millions of years under natural conditions down to mere minutes. This technology allows artificial coal production to be competitive with mining natural coal in a free market without any subsidies. If the coal-fired power plants were to use artificial coal as their fuel, their operation would become carbon neutral or even negative, which is a tremendous weapon in the arsenal to fight against climate change.

102011-10-21 Fri
14:00~15:00
R1203
David Koo
[UCO/LICK, UC Santa Cruz]
download PDF DEEP, AEGIS, & CANDELS: New Panchromatic Vistas of Distant Galaxies and AGN's
Abstract

I will give an overview of the Keck intermediate-redshift DEEP spectroscopic survey programs and the AEGIS multiwavelength surveys and reasons why they are particularly well suited for high-quality studies of distant galaxies and AGN's. After a brief summary of our major science findings, more details will be given 1) about a new measure of kinematics to track disk evolution, 2) about a rare class of very low metallicity, but very luminous, galaxies, and 3) about our discovery that galactic winds appear to be common at z ~1.4. I will close with an advertisement for a new 900+ orbit "public" imaging/grism survey with HST (CANDELS) that is beginning to open new doors for understanding very distant galaxies, AGN's, and supernovae.

112011-10-14 Fri
14:00~15:00
R1203
Dr. Scott Schnee
[NRAO]
download PDF Searching for the Origin of Multiplicity in Protostellar and Starless Cores
Abstract

I will present millimeter interferometric observations (CARMA and SMA) of starless cores and protostellar cores in nearby Milky Way molecular clouds. Using these observations, we find that many cores that were believed to be starless based on their lack of mid-infrared emission in fact have deeply embedded and low luminosity protostars. We find no evidence for fragmentation in the starless core sample, from which we concluded that binary and higher order systems do not begin to form until after the birth of the first protostar. Finally, I will show simulated observations of a numerical simulation of a collapsing core to predict what ALMA will be able to detect in the near-future.

122011-10-11 Tue
14:20~15:20
Physics R104
Prof. Lennox Cowie
[University of Hawaii]
*ASIAA/NTU Joint Colloquium*
download PDF Growing galaxies from start to finish
Abstract

Over the past two decades we have begun to understand how galaxies and their supermassive black holes form and evolve from the earliest times to the present. I will sketch how the development of new facilities in space and on the ground for observing at X-ray, UV/optical, and far-infrared wavelengths has driven this transformation in our understanding. I will also discuss some unresolved problems, such as where the photons needed to ionize hydrogen in the intergalactic gas are produced, why supermassive black holes form so early in the galaxy evolution process, and how much of early galaxy formation is obscured by dust.

132011-10-07 Fri
14:00~15:00
R1203
Prof. Len Cowie
[University of Hawaii]
download PDF Lyman alpha emitters from redshifts zero to seven
Abstract

In studying very high redshifts we only have two diagnostics: the UV continuum and the Lyman alpha emission line. The fraction of Lyman alpha emitters (LAEs) relative to UV-continuum sources has been suggested as a potential diagnostic of the evolution in the properties of the intergalactic gas. However, our understanding of the mechanisms governing the escape of Lyman alpha photons from galaxies is poor. I will discuss recent low redshift studies which allow us to study the properties of the LAES in great detail and which have found that LAEs are chosen from young and low-metallicity galaxies, so we might expect a high fraction of galaxies to be LAEs at very high redshifts. However, the current data on the fraction of galaxies that are LAEs at z>6 are confused. It may be that the fraction at z~6.5 is almost identical to that at z~3, which would suggest that we have not yet hit the point where the LAE fraction begins to change. Deep X-ray studies also do not seem to show much evidence for metal evolution, but we cannot quite get to the highest redshift (z~6) sources, even with the 4 Ms Chandra data.

142011-10-04 Tue
14:00~15:00
R1203
Prof. Evgeny (Uri) Griv
[Ben-Gurion University of the Negev]
*Special Seminar*
Waves and Their Instabilities in Astrophysical Disks
Abstract

Self-gravitating disk systems (disk-shaped galaxies, disks around massive objects, protostellar and protoplanetary clouds, planetary rings) are of great interest in astrophysics because of their widespread appearance. Such rapidly and nonuniformly rotating flat systems are highly dynamic and are subject to various collective instabilities of small-amplitude gravity perturbations (e.g., those produced by a spontaneous disturbance or, in rare cases, a companion system). This is because their evolution is primarily driven by angular momentum redistribution. The system may then fall toward the lower potential energy configuration and use the energy so gained to increase its coarse grained entropy. In this talk, I review recent studies of dynamics of astrophysical disks with special emphasis on their ring and/or spiral structures. I show that because of the long-range nature of the gravitational forces between particles, a self-gravitating disk exhibits collective (or cooperative) modes of motion -- waves in which the particles in large regions move coherently or in unison. The evolution of strophysical disks would depend on the ring and spiral structures produced in the system through internal instabilities of waves. The extent to which our results on the disk's stability can have a bearing on observable astrophysical disks is discussed as well.

152011-09-30 Fri
14:00~15:00
R1203
Dr. Masaaki Otsuka
[ASIAA]
Dust production in Planetary Nebulae
Abstract

Planetary Nebulae (PNe) represent a final stage in the evolution of low- to intermediate-mass stars with initially 1-8 solar mass; at the end of its life, a star of such mass evolves first into a red giant branch star, then an asymptotic giant branch star, and a PN. Dust production in the Milky Way galaxy predominantly comes from mass-loss during these end stages of stellar evolution. However, our understanding of dust creation and evolution largely comes from stars with metallicity close to the solar value. As sensitive observations of dust at lower metallicity are made in distant galaxies, it is imperative that we understand and characterize dust production at low metallicity within our own galactic environment. LMC PNe are ideal targets to study dust production and (dust) mass-loss rate in low- to intermediate-mass stars. Since the distance to the LMC is well determined and they evolved from stars with different metallicity, composition, and initial mass, we can estimate dust mass with less uncertainly and we can discuss relations between dust mass and properties of an ionized nebula and the progenitor star. I have been estimating dust mass in LMC PNe based on the data taken by Spitzer legacy projects SAGE and SAGE-Spec. I will show results of LMC PN dust and introduce ongoing other projects on dust in PNe.

162011-09-23 Fri
14:00~15:00
R1203
Dr. Amanda Bauer
[AAO]
Linking Star Formation Histories with the Growth of Stellar Mass
Abstract

As surveys of galaxy populations at high redshifts progress, it becomes increasingly urgent to understand how observed galaxies at high redshift map into those at lower redshift. In this talk, I investigate how and where stellar mass builds up over cosmic time by showing recent studies of the changing star forming properties of galaxies as a function of stellar mass and environment from redshift three to present.

172011-09-13 Tue
14:20~15:20
Physics R104
Prof. Richard Ellis
[Caltech]
*ASIAA/NTU Joint Colloquium*
Cosmic Dawn: The Quest for the First Galaxies
Abstract

A few hundred million years after the Big Bang, the hydrogen in deep space was ionized into its component protons and electrons. Theorists speculate this landmark event was caused by the birth of the first galaxies. Can powerful telescopes, probing back in cosmic history, directly witness this event? Large telescopes have already traced the evolutionary history of galaxies back to when the Universe was 1 billion years old. The first results from the Wide Field Camera 3 onboard Hubble Space Telescope give a glimpse at primitive stellar systems at yet earlier times. The lecture will address the progress and challenges of this fundamental quest for our origins, and discuss the future prospects with the next generation of 30 meter aperture ground-based telescopes.

182011-09-09 Fri
14:00~15:00
R1203
Dr. Ananda Hota
[ASIAA]
Discovery of a Spiral-host Episodic radio galaxy tracing Cluster Accretion (Speca)
Abstract

We report the discovery of a unique radio galaxy at z= 0.137, which could possibly be the second spiral-host large radio galaxy and also the second triple-double episodic radio galaxy. The host galaxy shows signs of recent star formation in the ultraviolet but is optically red and is the brightest galaxy of a possible cluster. The outer relic radio lobes of this galaxy, separated by ~1 Mpc, show evidence of spectral flattening and a high fraction of linear polarization. We interpret that these relic lobes have experienced re-acceleration of particles and compression of the magnetic field due to shocks in the cluster outskirts. From the morphology of the relics and galaxy distribution, we argue that re-acceleration is unlikely to be due to a cluster-cluster merger and speculate about the possibility of accretion shocks. The source was identified from Sloan Digital Sky Survey, Galaxy Evolution Explorer, NRAO VLA Sky Survey and Faint Images of the Radio Sky at Twenty-Centimetres survey data, but we also present follow-up optical observations with the Lulin telescope and 325-MHz low-frequency radio observations with the Giant Metrewave Radio Telescope. We briefly discuss the scientific potential of this example in understanding the evolution of galaxies and clusters by accretion, mergers, star formation and active galactic nucleus feedback.

192011-09-02 Fri
14:00~15:00
R1203
Prof. Richard de Grijs
[KIAA, Peking University]
Achievements and challenges in star formation
Abstract

What has been the most profound discovery, progress or idea that has emerged in astronomy over the last decade? And what will be the most important challenge in astronomical research in the next decade? These questions are at the heart of our discipline, but we rarely venture outside of our own niche areas. I will attempt to focus on the broad picture underlying the field of star formation and discuss the requisite conditions for sustained progress in this field, aided by recent achievements in the context of my group's star cluster research.

202011-08-26 Fri
14:00~15:00
R1203
Prof. Shinji Koide
[Kumamoto University]
A basis of resistive GRMHD simulation
Abstract

Ideal general relativistic MHD (GRMHD) simulations had revealed that magnetic reconnection is caused around rapidly rotating black hole spontaneously. To perform numerical simulations of such magnetic reconnection self-consistently, we use resistive GRMHD equations as the simplest approximation. I will talk about the basis for the simulation and some examples.

212011-08-19 Fri
14:00~15:00
R1203
Dr. Juan-Carlos Algaba Marcos
[ASIAA]
Multi-Frequency Parsec Scale Polarization Studies of Active Galactic Nuclei
Abstract

Although the continua of radio-loud Active Galactic Nuclei (AGN) are typically dominated by synchrotron radiation over virtually the entire spectrum, it is not clear whether the radio and higher-frequency emission originate in the same or different parts of the jet. several different radio–optical correlations based on polarization data have been found, suggesting that the emission regions may be cospatial. Our joint analysis of optical and VLBA polarization data shows that most BL Lac objects and some quasars have aligned VLBA-core and optical polarizations, although many quasars show no obvious relationship between their VLBA-core and optical polarization angles. We check if this can be explained by other physical properties, such as degree of polarization, core shift or magnetic field. We have also performed circular polarization (CP) analysis. The degree of circular polarization tends to increase with frequency. The implied degrees of order of the jet magnetic field are too high in most cases for the CP to be synchrotron in origin, requiring a substantial contribution from Faraday conversion.

222011-08-11 Thu
15:00~16:00
R1203
Prof. Arnab Rai Choudhuri
[Indian Institute of Science]
*Special Seminar*
Can we predict sunspot cycles?
Abstract

The 11-year sunspot cycle is believed to be produced by the dynamo mechanism in the convection zone of the Sun. After summarizing the relevant observational data, I shall give an overview of the solar dynamo problem. Then I shall address the question whether the current solar dynamo models are realistic enough for us to predict the strengths of future sunspot cycles.

232011-08-10 Wed
14:00~15:00
R1203
Dr. Jian-Rong Gao
[Delft University of Technology]
Detectors from Herschel to SPICA space telescope (** NOTE special time **)
Abstract

Astronomers know that the electromagnetic spectrum in the infrared region contains huge amount of useful information over our Universal. To discover the origins of galaxies, stars and planets, the Herschel Space Observatory (HSO) has been successfully built and launched in 2009 by the European Space Agency (ESA), where one of the instruments is HIFI (Heterodyne Instrument for the Far Infrared). Although HSO is busy with its science results, the next generation of infrared telescope, SPICA, to be jointly developed by the Japanese space agency (JAXA) and ESA, has been down-selected. SRON as the PI institute will contribute an imaging spectrometer to SPICA, which is called SAFARI and covers a wavelength range of 30–200 μm. The instrument with an unprecedented sensitivity and array size will help astronomers to watch distant stars and planets being born, revealing more about how the universe came to be. In this talk I will report the challenges and progresses in the development of the detection technology.

242011-08-09 Tue
11:00~12:00
R1203
Dr. Gordon Chin
[NASA/Goddard Space Flight Center]
*Special Seminar*
The Lunar Reconnaissance Orbiter (LRO): Recent Results from 2 years in Orbit around the Moon
Abstract

The Lunar Reconnaissance Orbiter (LRO) launched in June 18, 2009 with the objectives to finding safe landing sites, locate potential resources, characterize the radiation environment, and demonstrate new technology. The spacecraft was placed in low polar orbit (50 km altitude) for an initial 1-year mission under NASA’s Exploration Systems Mission Directorate. LRO has returned global data, such as day night temperature maps, a global geodetic grid, high-resolution color imaging and the moon’s UV albedo. There is particular emphasis on the polar regions of the Moon, a previously under explored region of the Moon, where continuous access to solar illumination may be possible and the prospect of water in the permanently shadowed regions at the poles exist. Although the objectives of LRO are explorative in nature, the payload includes instruments with considerable heritage from previous planetary science missions, has enabled a transition to a science phase under NASA’s Science Mission Directorate. In this talk, I will introduce each of the instruments and give an overview of their objectives and some of the LRO achievements after the 2 years of lunar observations. One notable event was the observations of LRO and the LCROSS impact. The combined observations from the LCROSS and LRO missions of the plume blasted into view by the spent Centaur upper stage of the Atlas rocket that propelled both spacecrafts to the Moon, offer a complex new view of the volatile inventory embedded in the lunar regolith.

252011-08-09 Tue
14:00~15:00
R1203
Prof. Ralf Klesson
[ITA]
*Special Seminar*
Star Formation Today and in the Early Universe
Abstract

Stars and star clusters are the fundamental visible building blocks of galaxies at present days as well as in the early universe. Identifying the physical processes that initiate and regulate stellar birth in our Milky Way can therefore contribute significantly to our understanding of star formation at high redshifts. Today, stars form by gravoturbulent fragmentation of interstellar gas clouds. The supersonic turbulence ubiquitously observed in Galactic molecular gas generates strong density fluctuations with gravity taking over in the densest and most massive regions. Collapse sets in to build up stars and star clusters. Turbulence plays a dual role. On global scales it provides support, while at the same time it can promote local collapse. Together with the thermodynamic properties of the gas it regulates the fragmentation behavior in star forming clouds. I discuss our current understanding of present-day star formation and speculate about the implications for the first and second generation of stars in the universe. Special emphasis lies on the distribution of stellar masses and their dependency on metallicity. I argue that the characteristic stellar mass is roughly constant for a wide variety of environmental conditions and that we expect a transition towards higher masses for metallicities below about 10^-5 times solar. I furthermore argue that the masses of zero-metallicity stars were smaller than previously thought and that Population III stars typically formed as members of binary or higher-order multiple stellar systems.

262011-08-05 Fri
14:00~15:00
R1203
Dr. Aigen Li
[University of Missouri]
[* Colloquium Cancelled *]
272011-07-29 Fri
14:00~15:00
R1203
Prof. Feng Yuan
[SHAO]
AGNs feedback at pc scale
Abstract

In a hot accretion flow, the radiation from the innermost region of the flow propagates outward and heats the electrons at large radii via Compton scattering. It has been shown in previous works that if the radiation is strong enough, $Lga 2%L_{rm Edd}$, the electrons at the Bondi radius ($r_Bsim 10^5 r_s$) will be heated to be above the virial temperature thus the accretion will be stopped. The accretion will recover after the gas cools down. This results in the oscillation of the black hole activity. In this paper we show that this mechanism is the origin of the intermittent activity of some compact young radio sources. Such intermittency is required to explain the population of these sources. We calculate the timescales of the black hole oscillation and find that the durations of active and inactive phases are $3times 10^4 (0.1/alpha)(M/10^8msun) (L/2%L_{rm Edd})^{-1/2}~{rm yr}$ and $10^5(alpha/0.1)(M/10^8msun)~{rm yr}$, respectively, consistent with those required to explain observations. Such kind of feedback occurring at parsec scale should be common in low-luminosity AGNs and should be considered when we consider their matter and energy output.

282011-07-22 Fri
14:00~15:00
R1203
Dr. Hsiang-Hsu Wang
[ASIAA]
Evidence for Radial Inflow in the Extended HI Disk of M83
Abstract

Numerical simulations as well as indirect observational evidence suggest that typical spiral galaxies are still accreting gas from the cosmic web even at present days. However, the corresponding mass flow onto the outer disk and the subsequent inward transport of material has not been observed directly. We combine interferometric data from the VLA (obtained as part of the THINGS survey) as well as single dish data from the 100m Effelsberg telescope to trace the distribution of atomic hydrogen (HI) far into the outskirts of the nearby spiral galaxy M83. We use these data to search for evidence of gas accretion of extragalactic origin onto the HI disk of M83. Using a novel Fourier analysis approach we extract detailed information about the gas kinematics throughout the HI disk of M83. We find a radial mass flow all the way from the extreme outer disk to the inner parts of the galaxy where the gas is consumed by star formation. The amount of material that is transported inwards is sufficient to form new stars at the observed current rate of ~ 2.5 Msun/yr, allowing the galaxy to evolve in a quasi steady state. For the first time, we can show that gas accretion and large-scale radial motions can solve the problem of short gas depletion times in spiral galaxies.

292011-07-15 Fri
14:00~15:00
R1203
Prof. Aeree Chung
[Yonsei University]
Redshift Search Receiver and Extragalactic Molecular Gas Studies
Abstract

Redshift Search Receiver (RSR) is a ultra-wideband spectrometer that covers the entire 3mm atmospheric window (75~111 GHz) simultaneously. It has been developed at the University of Massachusetts as the facility instrument for the Large Millimeter Telescope (LMT), a 50 meter radio telescope which has been being built in Mexico. While the LMT was under construction, the RSR had been commissioned on the Five College Radio Astronomy Observatory (FCRAO) 14 meter, carrying out several science programs. In this talk, I will present the highlights of the early extragalactic studies using the RSR, and give some updates on the current status of the instrument and the LMT.

302011-07-08 Fri
14:00~15:00
R1203
Dr. Edwige Chapillon
[ASIAA]
Molecular observations of protoplanetary disks
Abstract

Understanding the structure and evolution of disks surrounding low mass young stars is one of the key issues to study the process of planet formation. Nevertheless the overall properties of those protoplanetary disks are not yet well constrained by observations. Only a few molecules have been detected in the outer part of the disks (R > 30 AU) in the millimeter domain, but until now the observations remain spatially and sensitivity limited. Nonetheless, molecular tracers bring some constraints on the disk physical structure since different molecules sample different physical conditions. I this talk I will present a study of the gas-to-dust ratio in two suspected gas-poor disks surrounding the Herbig Ae star CQ Tau and MWC 758. I will also discuss observation of CN, HCN and H2D+ in T-Tauris disks.

312011-06-27 Mon
14:00~15:00
R1203
Dr. Greg Herczeg
[MPE]
*Special Seminar*
Observational diagnostics of accretion onto young low-mass stars
Abstract

Disk accretion controls many of the most important and physically interesting processes in the formation of a star and planetary systems. The accretion process drives powerful outflows that brakes stellar rotation, produces emission that heats and photoevaporates the disk surface, and viscously heating the disk interior where planet formation occurs. The lifetime of a disk, and consequently the time available for giant planet formation, is limited directly and indirectly by accretion. In this talk, I will review the evolution of accretion onto young stars and discuss the magnetospheric accretion paradigm for young stars, including new results from a large HST/COS survey of far-ultraviolet spectra of 30 T Tauri Stars (the DAO of Tau) and from recent optical surveys of accretion in nearby star-forming regions.

322011-06-17 Fri
14:00~15:00
R1203
(1) Dr. Naoyuki Tamura; (2) Dr. Hajime Sugai
[(1) Subaru Observatory; (2) IPMU]
(1) Wide-field fiber multi-object spectroscopy on Subaru: Current status & near future of FMOS, and a road continued to PFS. & (2) Prime Focus Spectrograph in SuMIRe Project
Abstract

(1) The unique combination of large light-gathering power and wide field of view on Subaru is exploited by FMOS for near-infrared spectroscopy. 400 fibers are distributed to configure on the 30 arcmin diameter field of view at the prime focus. The spectral coverage of the spectrographs is from 0.9 to 1.8 microns with an OH airglow suppression mechanism. So FMOS should be a powerful tool to characterize the galaxy and AGN populations at z>1 by efficiently observing major redshifted emission & absorption lines in the rest-frame optical regime. FMOS has been in operation for open-use observers since May 2010. The Guaranteed Time Observation (GTO) by the development team started at the same time and is on-going. In this presentation, I will give an overview of the instrument and summarize its current status with some demonstration of actual data. I will also present some preliminary scientific results from GTO. Recently, Prime Focus Spectrograph (PFS) has been proposed as a Subaru future instrument in a part of the SuMIRe (Subaru Mesurement of Images and Redshifts) project. This will be an even more powerful instrument in terms of field of view (1.3 deg diameter), multiplicity (2400 fibers), and spectral coverage (0.4-1.3um). At the end of this presentation, from my personal viewpoints, I will try to briefly comment on possible missing pieces in the existing galaxy surveys (including those potentially done by FMOS in future) and what should be targeted by PFS. ================================================ (2) Subaru telescope has two strengths: wide field of view and excellent image quality. As a future instrument taking an advantage of wide field of view, we are building Prime Focus Spectrograph (PFS) to carry out multi-fiber spectroscopy for the field of view of recently completed Wide Field Corrector. The PFS will have 2400 fibers, which are connected with 4 spectrographs with 3 color arms each. The PFS project consists of international collaborations. In order to make collaborations work effectively, we have recently established PFS project office. I will shortly summarize targets of PFS and the current status of PFS project.

332011-06-10 Fri
14:00~15:00
R1203
Dr. Jack Sayers
[Caltech]
Extra-galactic science from the Caltech Submm Observatory: massive galaxy clusters and high-redshift galaxies
Abstract

As the largest gravitationally bound objects in the universe, clusters are ideally suited for astrophysical and cosmological studies. I will present results from our ongoing program which has imaged the Sunyaev-Zel'dovich (SZ) effect in ~40 massive galaxy clusters with Bolocam. The SZ effect is sensitive to the integrated pressure in the intra-cluster medium (ICM), which contains ~90% of the baryonic mass of the cluster. Our data are able to constrain the morphology of the ICM, and to measure the pressure beyond the cluster virial radius. These clusters all have deep ancillary data (X-ray, lensing, etc.), and will allow us to probe for non-gravitational physics and to calibrate mass-observable scaling relations for use in cosmological studies. Bolocam's successor, MUSIC, will be deployed in late 2011 and will allow us to image clusters 10 times faster compared to Bolocam. MUSIC will also survey 10s of square degrees for dusty star-forming galaxies at high redshift, and will discover 100s of galaxies at z>3.

342011-06-09 Thu
14:00~15:00
R1203
Dr. Paula Stella Teixeira
[ESO]
*Special Seminar*
NGC2264: a veritable treasure trove for pre-main sequence circumstellar disk studies
Abstract

Circumstellar disks are a natural by-product of star-formation and they are the birthing sites of planetary systems. The characterization of these disks and their evolution is therefore crucial to understand and identify the initial conditions for planet formation. I will first present our Spitzer results on the characterization of the disk population in the young cluster NGC2264. The disked sources were identified by their excess emission between 3.6 and 24 microns, and classified according to their spectral energy distribution shapes. Our results have led us to hypothesize that there may be two distinct evolutionary paths for disks: a homologous one where the disk emission decreases uniformly in near- and mid-infrared wavelengths and throughout which most sources pass, and a radially differential one where the emission from the inner region of the disk decreases more rapidly than from the outer region. Whether a disk evolves in a homologously or radially depleted fashion may be indicative of the nature of planet formation in the disk. I will also present more recent results, using CoRoT data, on the structure of the inner disks and its relation to magnetospheric accretion. We found that disked sources have highly variable optical light curves, and many of these sources are actually AA Tau analogues, i.e., they can be modeled as having inclined magnetic field dipoles that truncate the disk at approximately the co-rotation radius. Follow-up VLT/Xshooter data is revealing variability in many spectral lines, from the UV to the NIR; this spectral line variability correlates well with the optical light curve and further confirms these sources as bona fide AA Tau-like systems. This cluster is going to be re-observed with Spitzer and CoRot simultaneously, promising many future exciting results on the 3D structure of inner disks and accretion geometry - a veritable treasure trove!

352011-06-08 Wed
14:00~15:00
R1203
Dr. Zuo-Min Tsai
[NTU]
*Special Seminar*
Applications of pHEMT Cascode Devices on ALMA Receiver
Abstract

For Band-1 and Band-2 of ALMA receivers, it is important to improve the gain and the bandwidth of the circuits. Instead of improving the MMIC process, we used the cascode device technique to improve the circuit performance. In this talk, I will introduce the technical challenge of the pHEMT cascode device, and how we overcome these issues. Based on the cascode device, two successful circuits (24 ~ 48 GHz Mixer and V-band VGLNA) will be demonstrated. To achieve better performance of the cascode device, the device modeling has to be improved. Therefore, the automatically model extractor will be introduced in the end of the talk. This model generator operated in room temperature and may be extended to the cryogenic device modeling.

362011-06-07 Tue
14:20~15:20
R104 Physics/Condensed Matter Building
Prof. Hitoshi Murayama
[UC Berkeley/IPMU]
*ASIAA/NTU Joint Colloquium*
Quantum Universe
Abstract

What is the Universe made of? How did it come to be? Why do we exist? This kind of fundamental questions about the Universe used to be just philosophy, but are now coming into the realm of quantitative science. The key is in quantum physics of elementary particles that determined the evolution of the Universe when it was very young. I will discuss this amazing connection between the large (the Universe) and the tiny (elementary particles), in the context of current and forthcoming experiments.

372011-06-03 Fri
11:00~12:00
R1203
Prof. Marc Chaussidon
[CNRS]
Early planetary accretion in the solar system: a view from short-lived radioactive nuclides and oxygen isotopes (** NOTE special time **)
Abstract

Recent developments of high precision Mg isotopic compositions in meteorites allow to show for the first time that short-lived 26Al (half life 0.73 Myr) can be used as a precise chronometer of condensation, accretion and differentiation processes which took place around the young Sun. Primitive meteorites contain components which, according to their Mg and O isotopic compositions, could be the fragments of planetesimals which differentiated very early, in the first Myr of the solar system, i.e. much before the formation of the parent bodies of chondrites. These results, which are against "classical" ideas, are in agreement with recent planetary models which take into account turbulence to promote the formation of clumps of particles dense enough to undergo gravitational instabilities.

382011-05-31 Tue
10:30~11:30
R1203
Dr. Ramon Brasser
[Observatoire de la Cote d'Azur]
*Special Seminar*
A dynamical approach to the quest for habitable worlds (** NOTE special time **)
Abstract

At present the discovery rate of extrasolar planets is steadily increasing and is about to explode when the data from NASA's Kepler mission becomes available. This automatically leads to the question of whether any of these worlds are habitable. In this presentation I shall give an overview of some of my previous research results to familiarise the audience with my work. I demonstrate that I have acquired certain skills that allow me to put constraints on the habitability of exoplanets, based on the evolution of their obliquity and whether or not any satellites are present.

392011-05-31 Tue
14:20~15:20
Physics/Condensed Matter Building R104
Prof. Frank Shu
[ASIAA]
*ASIAA/NTU Joint Colloquium*
Nuclear Energy After Fukushima
Abstract

After the tragic events in Japan, nuclear power is much in the news, and re-evaluations are occurring on both sides of the nuclear debate. Pragmatic scientists and engineers who have studied the problem agree that of the available energy technologies, only nuclear power has the potential to alleviate our current overwhelming dependence on fossil fuels. In Taiwan, the choice is even clearer. As a commentator on National Public Radio in the United States has put it: if you are anti-CO2 and anti-nuclear, then you are pro-blackouts. Phrased in terms of either energy self-sufficiency or an antidote to climate change, the challenge before us must be how to make nuclear power safer, cheaper, and more proliferation resistant, with a tenable method for disposing the radioactive waste. A solution may exist in molten salt reactors that operate on the thorium cycle, but mobilizing public support for such an approach must increase the perceived benefits of nuclear power while reducing its risks.

402011-05-30 Mon
14:00~15:00
R1203
Dr. Keiichi Asada
[ASIAA]
*Special Seminar*
Toward complete understanding of AGN jets with VLBI approach
Abstract

Jets emanating from the active galactic nuclei (AGN) are one of the largest objects in the universe. Some jets travel more than 1 Mpc, keeping highly collimated structure. Based on statistical studies, it has been known that jets are highly accelerated, in some cases, up to bulk Lorentz factors of 50!! We are reaching an important clue to understand the jet phenomena. However, the most essential subjects, how jets are formed, accelerated and collimated, are still unclear. Focusing on these issues, we have conducted VLBI observations to probe the structure of the magnetic fields in the jets and velocity field of the jet. As the results, we have revealed that several jets have a helical magnetic field, and have specified the acceleration and collimation region of the AGN jet at longer range from the core ( from 500 to 10^{6} r_{s} from the black hole). Those properties can be explained by MHD jet model. The remaining issue, formation mechanism of the jet, would be investigated by future submm VLBI.

412011-05-27 Fri
14:00~15:00
R1203
Prof. Albert Zijlstra
[University of Manchester]
Formation and evolution of planetary nebulae
Abstract

Planetary nebulae reflect the death throes of Sun-like stars, when they eject between 20% and 80% of their mass of the star through a 'super'-wind. This ejection process determines the white dwarf mass distribution, and is the origin of up to half of the gas and dust in the ISM. The cause, evolution and composition of the superwind is still a matter of debate. Observations of planetary nebulae and their progeny, AGB stars, provide important constraints on the superwind and its origin. I will discuss new observational results, including mass loss at low metallicity, the fate of iron, the formation process of PAHs, and the formation and photo-evaporation of dust disks. I will also discuss the effect of angular momentum which for much of stellar evolution is in cold storage in the stellar system.

422011-05-20 Fri
14:00~15:00
R1203
Prof. Sujan Sengupta
[Indian Institute of Astrophysics]
Cloudy Atmosphere of Brown Dwarfs : Theory vs. Observations
Abstract

Brown dwarfs inhabits the realm intermediate to less massive stars and giant planets. They are born like a star but fail to sustain nuclear burning inside their core. Consequently they could not become a star. The atmosphere of brown dwarfs are very much similar to hot giant planets. Therefore, understanding the atmosphere of brown dwarfs provides important insight onto the atmosphere of giant extra-solar planets. Depending on their spectra, brown dwarfs are divided into two classes - L and T dwarfs. The relatively hotter brown dwarfs belong to the subclass of L dwarfs. Due to incomplete gravitational settling, the atmosphere of L dwarfs should contain condensates mainly of silicate. The indirect evidence for the presence of dust cloud in the atmosphere of L dwarfs comes from the diagnosis of its optical and infra-red spectra. The direct evidence of dust comes from the detection of linear polarization in the optical bands. In the present talk, I shall discuss the physical properties of the atmosphere of L brown dwarfs derived from the detail theoretical analysis of the observed spectra as well as the observed photo-polarimetric data.

432011-05-18 Wed
14:00~15:00
R1203
Dr. Ming-Chang Liu
[ASIAA/CRPG-CNRS]
*Special Seminar*
The "HOTTEST" mineral in the Solar System and Irradiation from the Proto-Sun
Abstract

The formation of the Solar System has long fascinated astronomers and planetary scientists alike. Although we cannot travel back 4.5 Gyr to observe how did our own planetary system form, highly sophisticated instrumentation has enabled astronomers to gain a lot of insights into the details of the collapse of molecular cloud cores as the first step of forming new planetary systems. However, direct analysis of samples in terrestrial labs should yield superior data that are impossible to obtain by remote sensing. Therefore, samples of primitive meteorites so far provide the most critical information on the earliest history of Solar System formation. Infrared observations have revealed the existence of dust in young disks. Results from Chandra X-ray space telescope also suggest that young stars are associated with strong flare activities, and thus are capable of releasing high flux of energetic particles. To understand the timing of conversion from presolar dust to solar dust in the solar disk, one could use meteorites, as they witnessed the formation of the Solar System. Meteorites consist of less refractory components (T < 1400K), and higher temperature solids (1450K < T < 1750K). Among high temperature phases, hibonite (CaAl12O19) is one of the oldest solids in the Solar System, forming at the temperatures of ~1750K as either direct condensates from the nebula gas, or residues after heating of low temperature material. Two groups of hibonites could be distinguished based on the mineralogy and fossil record of 26Al, a short-lived radionuclide with a half-life of 0.72 Myr: Spinel-HIBonite spherules (SHIBs) contain 26Al/27Al ranging from 1×10-5 to 7×10-5, and PLAty-hibonite Crystals (PLACs) are characterized by very low apparent 26Al/27Al (<<1×10- 5). Interestingly, the inferred 26Al abundances are found to be anti-correlated with the magnitude of enrichments or depletions of a neutron-rich isotope, 50Ti. Large δ50Ti variations (~30%) are exclusive to PLACs, and SHIBs carry much smaller anomalies (<1%). Such observations suggest that PLACs should have formed in a highly heterogeneous and 26Al-free disk, probably at the very beginning of the Solar System. On the other hand, the relatively homogeneous δ50Ti but variable 26Al/27Al in SHIBs indicate that SHIB formation occurred after PLACs, and was contemporaneous with homogenization of 26Al inside the disk, which was delivered from an external source. That PLACs carry fossil records of 10Be suggests that the proto-Sun had become a powerful energetic particle source before the arrival of 26Al. All these data indicate that conversion of presolar dust to solar dust should have started as early as Class I stage.

442011-05-13 Fri
14:00~15:00
R1203
Dr. Seokcheon (Sky) Lee
[ASIoP]
Constraints on dark energy : challenges and pitfalls
Abstract

The current accelerating expansion of the Universehas been connoted consistently by a wide scope of cosmological data. It has been known that the geometrical tests like standard candles (in the form of SNIa) and standard rulers (in CMB and BAO) consistent with the so called LambdaCDM(LCDM) model. Also the perturbational tests including the linear growth factor (so called EG test) and clusters (cluster numbers, WL, and SZe) are claimed to be compatible with LCDM. We demonstrate the challenges and pitfalls in these statements. It is too early to make any conclusion for the origin of the present accelerating universe with the current observables.

452011-05-06 Fri
14:00~15:00
R1203
Prof. Xander Tielens
[Leiden Observatory]
Polycyclic Aromatic Hydrocarbon molecules in Space
Abstract

Strong IR emission features at 3.3, 6.2, 7.7, 8.6, and 11.2 μm are a common characteristic of regions of massive star formation in the Milky Way and nearby galaxies and out to redshifts of ~3. These features are carried by large (∼ 50 C-atom) Polycyclic Aromatic Hydrocarbon molecules, which are pumped by the strong FUV photon flux from these stars. ISO/SWS and Spitzer/IRS studies have revealed the richness of the interstellar IR emission spectrum and the variations therein. These variations reflect variations in the physical conditions of the emitting regions. Over the last 10-20 years, extensive experimental and theoretical studies have elucidated the intrinsic infrared properties of large PAH molecules and their dependence on the molecular characteristics. We are now reaching a stage where we can use the observations of the IR emission spectrum as diagnostic tools to determine the physical conditions in the emitting regions of particular regions of star formation. Observations have shown that PAH molecules are abundant and ubiquitous in the interstellar medium. Conversely, PAHs may also be a dominant “force” in the interstellar medium. In particular, PAHs dominate the photoelectric heating of interstellar gas and thereby shape the phase (cloud/intercloud) structure of the ISM. PAHs are also the dominant negative charge carriers inside dense molecular cloud cores and, hence, regulate the charge balance of molecular gas. Thus, PAHs control the ambipolar diffusion process and the onset of gravitational collapse. Because the IR emission features dominate the IR spectrum of regions of massive star formation, these bands are often used as proxies to determine the importance of star formation on galactic scales. Specifically, the importance of star formation versus AGN activity for the luminosity source of ULIRGs is based upon a quantitative interpretation of the observed PAH emission from galactic nuclei. I will review these different aspects of interstellar IR spectra, the extensive laboratory studies on the spectroscopic and chemical properties of PAHs, their relationship to the intrinsic properties of PAHs, the role of these PAHs in shaping the universe around us – in particular through the star formation process – and the use of PAH emission spectra as quantitative indicators of star formation.

462011-05-04 Wed
14:00~15:00
R1203
Dr. Thomas Greve
[Niels Bohr Institute Dark Cosmology Centre]
*Special Seminar*
Towards an understanding of the gaseous origin and evolution of galaxies - what will the coming years bring?
Abstract

A key piece to the puzzle of galaxy origins can be traced back to that benchmark epoch of Cosmic reionization - lasting from a few hundred million years (z~15) to approximately one billion years after the Big Bang (z~6) - where the first luminous sources (stars, galaxies, and accreting black holes) ionized their neutral surroundings. Only in the last few years has this new frontier of the z > 6 Universe opened up, with sizable samples of various galaxy types (from QSOs to GRB host galaxies) gradually becoming available for systematic and detailed studies. Thanks to the remarkable sensitivities and observing capabilities of today's leading (sub)millimeter interferometers (e.g. ALMA, SMA, IRAM PdBI and CARMA, in particular) we are now on the verge of delineating the ISM properties of z > 6 galaxy samples for the first time. Such an observational endeavor is essential if we are to gain a deep and comprehensive picture of how the first galaxies formed and evolved.

472011-04-29 Fri
14:00~15:00
R1203
IAA Outing
[ASIAA]
Cancelled due to ASIAA outing
Abstract

We are trying to reschedule Prof. Albert Zijlstra's visit, who was originally scheduled to give a talk on this date. Please stay tuned!

482011-04-22 Fri
11:00~12:00
R1203
Dr. Clive Dickinson
[University of Manchester]
Early Planck Results in the Galaxy
Abstract

I will give an overview of the Planck mission and the recent Early Planck Results papers (submitted to A&A January 2011). I will present the results of the Galactic papers from these early papers, focussing on the Anomalous Microwave Emission (AME). Data from Planck, combined with ancillary data (WMAP, radio data, DIRBE etc.), has allowed us to construct precise spectra for Galactic regions such as Perseus and Rho Ophiuchus molecular clouds. The spectra show strong evidence for AME, which can be readily fitted by electric dipole radiation from small spinning dust grains.

492011-04-15 Fri
14:00~15:00
R1203
Dr. Helmut Dannerbauer
[CEA-Saclay]
(Sub)millimeter observations of Distant, Massive Galaxies
Abstract

In order to understand galaxy formation it is of primary importance to obtain sensitive observations of the emission of dust, proportional to the rate of star formation, and of gas, the primary ingredient of star formation. Both are major goals of the Atacama Large Millimeter/submillimeter Array (ALMA). Interesting new science, though, can be done now, while waiting for ALMA. Two major questions in galaxy formation and assembly are: 1) do dusty starbursts exist at very high-redshifts, and 2) what is the dominating mode of star-formation in distant, massive galaxies, either galaxy mergers or long-lasting cold gas accretion. To shed light on these topics, I will present our on-going Herschel and IRAM Plateau de Bure Interferometer observations of two important star-forming galaxy populations in the distant universe: submillimeter selected galaxies (SMGs) and massive disk galaxies at z=1.5. Finally, I will discuss the prospects of the synergistic combination of ALMA and Herschel observations on these high-redshift massive, star-forming galaxies.

502011-04-08 Fri
14:00~15:00
R1203
Roberto Galvan-Madrid
[CfA/UNAM]
On the Formation of the Most Massive Stars in the Galaxy
Abstract

The 'really' massive stars (those with more than 10 to 20 solar masses) likely start to ionize their surroundings before they reach their final mass. How can they accrete in spite of the presence of over-pressurized gas? We present results of Submillimeter Array (SMA) and Very Large Array (VLA) studies of massive-star formation regions in the early stages of ionization: Molecular-line observations at resolutions from a few arcsec to 0.3 arcsec reveal the presence of rotation, infall, and/or outflow from parsec scales to <0.05 pc. Small groups of massive (proto)stars are found at different evolutionary stages. The innermost ionized gas is sometimes found to have organized motions, probably in the form of outflow and/or rotation. Multiepoch observations of the free-free continuum reveal significant flux variations in timescales of years, attributable to interactions with the surrounding molecular gas. These observations, as well as recent models and numerical simulations of HII region evolution in star-forming accretion flows, favor a picture in which: i) These very massive stars form in accretion flows that are partially ionized. ii) The cores from which these stars form keep accreting material from their enviroment (clump).

512011-04-01 Fri
14:00~15:00
R1203
Dr. Jonathan Sievers
[CITA]
Cosmology from 17,000 Feet: Results from the Atacama Cosmology Telescope
Abstract

The Atacama Cosmology Telescope (ACT) is observing the Cosmic Microwave Background (CMB) from high in the Chilean Andes. The CMB provides a snapshot of the universe when it was only 400,000 years old, long before the formation of any stars or galaxies. The nearly uniform density (to a few parts per hundred thousand) means that well understood linear physics describes the physics of the CMB and lets us reliably tranform observations of the CMB into constraints on fundamental parameters of the cosmos. ACT provides a significant improvement to our knowledge of the CMB on small (few arcminute) scales. We present the results from the first full season of ACT data and what we learn from them, including better limits on the number of relativistic species, the initial power spectrum from inflation, early helium density, potential contributions to structure formation from cosmic strings, and the imprint of galaxy clusters on the CMB.

522011-03-29 Tue
14:20~15:20
Condensed Matter Building R104
Prof. Paul Ho
[ASIAA]
*ASIAA/NTU Joint Colloquium*
Origins of Everything: Precision Astrophysics
Abstract

With the modern advances in device physics, novel materials, improved engineering, high speed computing, and space platforms, astronomy has made enormous progress in the last two decades. Precision astrophysics in the spatial domain, energy domain, and time domain, has allowed us to study the "Origins of Everything", from life to the formation of planets and stars, and from galaxies to the beginning of the Universe. In Taiwan, in this past decade, we are engaging these frontiers of research. We have access to the best instruments in the world, and we are building some of them. It is a great time to be studying physics. In this talk, we will look at three important problems: extrasolar systems, black holes, and cosmology.

532011-03-25 Fri
14:00~15:00
R1203
Dr. Dan Werthimer
[UC Berkeley Space Science Lab]
IS ANYBODY OUT THERE? The Search for ET with help from Eight Million Volunteers
Abstract

Werthimer will discuss the possibility of life in the universe and the search for radio and optical signals from other civilizations. Berkeley's SETI@home project analyzes data from the world's largest radio telescope using desktop computers from millions of volunteers. SETI@home participants have contributed millions of years of computer time and have formed one of Earth's most powerful supercomputers. Users have the small but captivating possibility their computer will detect the first signal from a civilization beyond Earth. Werthimer will also discuss other citizen science projects, next generation radio telescopes, as well as speculate on when Earthlings might discover other civilizations.

542011-03-18 Fri
14:00~15:00
R1203
Prof. Yasuhiro Hashimoto
[NTNU]
Galaxies and Environments
Abstract

Galaxies are the building blocks of the Universe. The history of galaxies -- when and how they formed, and how they have evolved -- is a topic of enormous current astronomical interest. Many lines of evidence have made it abundantly clear that there has been substantial evolution of the properties and populations of galaxies during recent epochs. Although it is possible that some portion of the evolutionary changes observed are due to causes internal to the individual galaxies, there are reasons for suspecting that at least some part of the evolution is driven by external forces in the galaxies' environment. Comparing populations of galaxies in the various environments will give us one of the most valuable opportunity to observe galaxy evolution in action, with the eventual goal of understanding one of the fundamental issues of modern astronomy, the evolution and formation of galaxies. I will review the scientific roles of the environmental investigations of galaxies in modern astronomy, with some emphasis on the galaxy survey and multi-band observations evolving X-ray.

552011-03-16 Wed
14:00~15:00
R1203
Prof. Chao-Lin Kuo
[Stanford University]
*Special Seminar*
Science with Cosmic Microwave Background Polarization
Abstract

Precise measurements of polarization in the cosmic microwave background (CMB) provide important information on early universe. In particular, CMB polarization will shed light on the initial fluctuations, which are thought to be generated by a quantum process during Big Bang. In this talk, I will give an overview of science opportunities with CMB polarization and describe a series of South Pole-based experiments (BICEP, BICEP2, Keck, and POLAR).

562011-03-11 Fri
14:00~15:00
R1203
Prof. Rachel Webster
[University of Melbourne]
The Epoch of Reionisation: the MWA Experiment
Abstract

The birth of the first stars and black holes is currently unobservable, buried in a sea of neutral Hydrogen in a time we currently call the ‘Dark Ages’. Detailed numerical simulations predict the sequence of events which may have unfolded, but we do not yet know when the first sources turned on, nor what their characteristics were. There are two wavebands which appear to be promising for the first observations: the infrared and long radio wavelengths. This talk will describe the expected radio signatures of redshifted 21cm emission from Hydrogen, and the new telescopes which are attempting to detect these signals. In addition, a description will be given of some of the potential science which will be accessible once the web of 21cm emission is observed.

572011-03-10 Thu
14:00~15:00
R1203
Dr. Tsz Yan Lam
[IPMU]
*Special Seminar*
Analytical modelings in large-scale structure
Abstract

The past decade is the fruitful decade of cosmology: observational improvements in the CMB/ galaxy surveys/ supernova; computational advancements in collisionless/hydro simulations; as well as the theoretical developments in cosmology. We are now in the era of precision cosmology -- the next generation of sky surveys (Planck/ LSST/ HSC) aims at constraining cosmological models in the percent level. In order to fully utilize the potential of the observational data, we must understand how non-linear gravitational evolution affects the signals. Better theoretical models are needed to achieve the percent level goal. In this talk I will discuss some of recent developments of theoretical modelings of large-scale structure and their observational implications in constraining cosmological models.

582011-03-04 Fri
14:00~15:00
R1203
Prof. Michael Strauss
[Princeton University]
Clustering of Quasars on Small and Large Scales
Abstract

The clustering of quasars is an important clue to the nature of the dark matter halos in which they sit, and the types of galaxies that host them. I will present results on the clustering of quasars as a function of redshift, which demonstrate that they tend to occupy dark matter halos of order several x 10^12 solar masses at all redshift. On scales of less than 1 Megaparsec, binary quasars give clues to the mechanism by which material is fed to the central black hole, and can test models by which galaxy mergers trigger quasar activity. I will describe methods for identifying binary quasars from imaging and spectroscopic data, and conclude with a look to the next generation of imaging and spectroscopic surveys to find more such objects.

592011-03-03 Thu
14:00~15:00
R1203
Dr. Olivier Dore
[JPL/Caltech]
*Special Seminar*
PLANCK Early Results: Cosmic Infrared Background Anisotropies
Abstract

Since it reached the Lagrange point L2 in August 2009, the PLANCK satellite has been observing the sky at frequencies from 30 to 857 GHz, measuring not only the Cosmic Microwave Background, but also everything else in the Universe that radiates at these frequencies. The first scientific results from PLANCK cover a wide range of galactic and extragalactic astrophysics, including clusters, extragalactic radio sources, the Cosmic Infrared Background, and spinning and thermal dust in the Milky Way. In this talk, after briefly reviewing them I will focus on Planck early measurements of the Cosmic Infrared Background.

602011-03-02 Wed
14:00~15:00
R1203
Mr. Randy Landsberg
[KICP Chicago]
*Special Seminar*
Connections: Science, Museums & People
Abstract

Education and outreach has become an important aspect of scientific research in the United Sates. I will describe a few innovative programs and strategies developed in Chicago to share on-going research with broad audiences and to connect scientists with the general public. I will first demonstrate effective ways to integrate current research into museums and planetariums including: data visualization, researchers presenting in museums, and professional development for museum and planetarium staff. I will then review a successful science enrichment program for high school students (i.e., program graduates enrolled as science majors in college at a rate five times their peers).

612011-03-01 Tue
14:20~15:40
Condensed Matter Building R104
Prof. Hsiao-Wen Chen
[University of Chicago]
*ASIAA/NTU Joint Colloquium*
Gamma-ray Burst Afterglows as Cosmic Probes
Abstract

Gamma-ray bursts are among the most energetic events in the universe. Many bursts are followed by extremely luminous optical afterglows that can serve as a sensitive probe of "dark", intervening baryonic matter in space. I will review recent progress in our understanding of interstellar medium and intergalactic matter in the distant universe, through observations of long-duration gamma-ray bursts.

622011-02-21 Mon
14:00~15:00
R1203
Mr. David Atlee
[Ohio-State University]
*Special Seminar*
The AGN-Starburst Connection in Low Redshift Galaxy Clusters from Multiwavelength Data
Abstract

Clusters of galaxies have long been used as laboratories for the study of galaxy evolution because the processes that impact morphology and star-formation rates (SFRs) in dense environments occur most rapidly in clusters. I present results from a study of AGN and star-formation in 8 low-redshift galaxy clusters. I will show spectral energy distributions (SEDs) constructed from visible and MIR observations of cluster galaxies and the models used to fit them. These fits measure stellar masses and SFRs of the cluster members, which we use to predict the X-ray luminosity of each cluster member. X-ray luminosities in excess of the predictions indicate the presence of an AGN, which can also be identified based on the shapes of their SEDs. I will compare the two classes of AGN and discuss the properties of their host galaxies. I also examine the duty cycle of AGN in galaxy clusters, which indicates that typical black holes in galaxy clusters are not growing significantly with respect to their host galaxies at z = 0. Finally, I measure the relationship between star-formation, accretion and environment within clusters, which is consistent with earlier work on the SFR-density relation, and argue that we need suites of cosmological, hydrodynamic simulations of galaxy evolution in clusters.

632011-02-11 Fri
14:00~15:00
R1203
Prof. Albert Kong
[NTHU]
A GHz-GeV view of compact objects in globular clusters
Abstract

By combining high resolution and high sensitivity multiwavelength (GHz to GeV) observations, the study of compact objects (e.g. neutron stars, cataclysmic variables, and black holes) in globular clusters is in very rapid progress. Not only we can identify the nature of many faint (Lx < 1e33 erg/s) globular cluster X-ray sources and discover a population millisecond pulsars, we can also make use of the statistics to investigate the stellar dynamics and evolution of globular clusters. Moreover, it has been proposed that globular clusters may house black holes. In particular, G1 in M31 is the most luminous star cluster in the Local Group and has been claimed, based on kinematic studies, that it hosts a ~20000 solar-mass intermediate-mass black hole (IMBH). By matching images taken with the Hubble Space Telescope, ground-based telescopes, and Chandra, we for the first time can localize the X-ray emission and determine its nature. Lastly, by using deep ATCA observations, we constrain the mass of a possible IMBH in two Galactic globular clusters.

642011-01-28 Fri
14:00~15:00
R1203
Dr. Paul Woods
[University of Manchester]
The Chemistry of Extragalactic AGB Stars
Abstract

Carbon stars with high mass-loss rates in the Large Magellanic Cloud have recently been subject of renewed interest through their compelling Spitzer IRS spectra. These dusty evolved objects must have a thick molecular envelope, and the capabilities of the ALMA interferometer mean that we will be able to observe the molecular content of these stars in a reasonable amount of time. I will talk about my work that investigates the rich chemistry in the circumstellar envelopes of these low-metallicity objects, which is very different to that of Galactic carbon stars. For a given mass-loss rate, penetration of UV radiation into the envelope is greater, meaning that the molecular envelope is smaller, and that the chemistry is warmer. The CO molecule is not as dominant as it is in Galactic stars, and acetylene becomes more abundant at certain radii. In general, chemistry is more complex, with larger hydrocarbons and cyanopolyynes reaching abundances comparable to those of smaller members of the same family. It is clear that one cannot simply scale Galactic carbon-rich circumstellar abundances to according to metallicity.

652011-01-21 Fri
14:00~15:00
R1203
Dr. Larry Nittler
[Carnegie Institution of Washington]
Cometary Dust in the Solar System
662011-01-14 Fri
14:00~15:00
R1203
Dr. Manash Samal
[ARIES]
Star formation activity in the vicinity of Galactic HII regions
Abstract

Massive stars (M > 8 M⊙) have profound effect on the parental molecular cloud. The formation and early evolution of a massive star, evolution of associated stellar cluster and the effect of harsh radiation field on the surrounding environment have been the subject of many theoretical and observational studies. Understanding these feedback processes, their mode of interaction with the surrounding medium are vital to have an improved understanding of star formation processes within a complex. In this talk, I shall focus on recent results obtained with multiwavelength observations around classical HII regions, which are created by massive OB stars. We particularly attempt to combine various multiwavelength observed components into a coherent model to explore the process that may influence the formation of young stellar objects in these regions. Our analysis shows evidence of induced star formation at the borders of these HII regions, which seems likely to be due to the radiation driven implosion, dynamical instability of advancing ionization front or the collision of swept up matter. I will also discuss properties of the associated clusters.

672011-01-13 Thu
14:00~15:00
R1203
Dr. Taro Kotani
[Aoyama Gakuin University]
*Special Seminar*
Multi-wavelength Observation Campaigns for Microquasars
Abstract

Microquasars are X-ray binary systems with a relativistic high-energy jet. Though they have been studied for more than a decade, the fundamental physics of the jet, such as the formation, acceleration, and collimation mechanism, is still remain a mystery. To understand the jet, whose physical parameters range over several orders of magnitude, we need multi-wavelength observation campaigns. We have performed campaigns for the microquasars SS433, Cyg X-3, and GRS 1915+105, and are going to observe Cyg X-3, which is currently in the active state in which several gigantic flares are expected.

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