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Activity > Colloquium

Colloquium (2017)

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)

NEXT Colloquium: 2017-03-01 Wed 14:20~15:20 [R1203]
Speaker:Samantha Lawler
Topic:Does our Solar System Need to have Another Planet?
Abstract:The orbital element distribution of trans-Neptunian objects (TNOs) with large pericenters has been suggested to be influenced by the presence of an undetected, large planet at >200 AU from the Sun. To find additional observables caused by this scenario, we present here the first detailed emplacement simulation in the presence of a massive ninth planet on the distant Kuiper Belt. We perform 4 Gyr N-body simulations with the currently known solar system planetary architecture, plus a 10 M_earth planet with similar orbital parameters to those suggested by Trujillo & Sheppard or Batygin & Brown, and thousands of test particles in an initial planetesimal disk. We find that including a distant super-Earth-mass planet produces a substantially different orbital distribution for the scattering and detached TNOs, raising the pericenters and inclinations of moderate semimajor axis (50 < a < 500 au) objects. We test whether this signature is detectable via a simulator with the observational characteristics of four precisely characterized TNO surveys. We find that the qualitatively very distinct solar system models that include a ninth planet are essentially observationally indistinguishable from an outer solar system produced solely by the four giant planets. We also do not find any evidence for clustering of orbital angles in our simulated TNO population, and further simulations find that an additional planet causes significant changes in the orbits of known distant TNOs. Wide-field, deep surveys targeting inclined high-pericenter objects will be required to distinguish between these different scenarios.
NEXT Special Seminar: 2017-03-06 Mon 14:20~15:20 [R1203]
Speaker:Paulo Freire
Topic:Testing the nature of gravitational waves with observations of binary pulsars
Abstract:In this talk, I will review some of the principles of pulsar timing, and review some of the results from the timing of binary pulsars from previous work. These include the observation of gravitational waves (GWs) in the energy loss of the "Hulse-Taylor" double neutron star, almost 40 years before the LIGO observation. I then introduce ongoing work, which tests the emission of GWs with far more accuracy than in the Hulse-Taylor pulsar, and new detections of the emission of gravitational waves in pulsar-white dwarf systems, which introduce strong constraints on the nature of GWs. In particular, we are able to exclude, within observing precision, any dipolar components of gravitational radiation, showing that they are almost purely quadrupolar. These results are then used for some of the most stringent tests of general relativity and alternative theories of gravity ever accomplished.
No. Time/Place Speaker Topic / Abstract
download PDF: download talk PDF file
12017-08-23 Wed
14:20~15:20
R1203
I-Non Chiu
[ASIAA]
TBD
Abstract

TBD

22017-07-26 Wed
14:20~15:20
R1203
Li-Ting Hsu
[ASIAA]
TBD
Abstract

TBD

32017-06-21 Wed
14:20~15:20
R1203
Yu-Yen Chang
[ASIAA]
TBD
Abstract

TBD

42017-06-07 Wed
14:20~15:20
R1203
Changbom Park
[KIAS]
TBD
Abstract

TBD

52017-06-06 Tue
14:20~15:20
R104, CCMS
Changbom Park
[Korea Institute for Advanced Study (KIAS)]
*ASIAA/NTU Joint Colloquium*
TBA
Abstract

TBA

62017-05-31 Wed
14:20~15:20
R1203
Ming Sun
[University of Alabama Huntsville]
TBD
Abstract

TBD

72017-05-10 Wed
14:20~15:20
R1203
Kevin Koay
[ASIAA]
TBD
Abstract

TBD

82017-05-03 Wed
14:20~15:20
R1203
Xiaohu Li
[ASIAA]
TBA
Abstract

TBA

92017-04-26 Wed
14:20~15:20
R1203
Ai-Lei Sun
[ASIAA]
TBA
Abstract

TBA

102017-04-19 Wed
14:20~15:20
R1203
Andrew Youdin
[University of Arizona]
TBA
Abstract

TBA

112017-04-12 Wed
14:20~15:20
R1203
Hayato Shimabukuro
[Observatoire de Paris]
TBA
Abstract

TBA

122017-03-29 Wed
14:20~15:20
R1203
Kenny Vilella
[Institute of Earth Sciences, Academia Sinica]
TBA
132017-03-23 Thu
14:20~15:20
R1203
Ke-Jung Chen
[NAOJ]
*Special Seminar*
TBA
Abstract

TBA

142017-03-22 Wed
14:20~15:20
R1203
Ziri Younsi
[University of Frankfurt]
TBA
Abstract

TBA

152017-03-20 Mon
14:20~15:20
R1203
Andrew Mann
[University of Hawaii at Manoa]
*Special Seminar*
TBD
Abstract

TBD

162017-03-16 Thu
14:20~15:20
R1203
Toshiya Namikawa
[Stanford University]
*Special Seminar*
Cosmology with cosmic microwave background polarization
Abstract

One of the promising cosmological probes in the next decades is the CMB polarization. While CMB temperature anisotropies have been already measured very precisely, CMB polarization, in particular a twisting pattern in the polarization map (B mode) is not well measured. The detection of B mode at more than degree angular scale opens new window into the inflationary universe and high energy physics beyond the standard model. Precise polarization data also enables us to measure gravitational lensing of CMB which is a key probe to understand the properties of neutrinos, dark matter and dark energy. In this talk, I will present analysis of the gravitational lensing and cosmic birefringence measurements with CMB polarization data taken from BICEP2/Keck Array experiments. I will also talk about synergy between CMB experiments and galaxy surveys such as the galaxy-lensing cross correlation with Subaru-Hyper Suprime Cam and CMB experiments, and delensing B mode with mass tracers.

172017-03-15 Wed
14:20~15:20
R1203
Sofia Wallstrom
[ASIAA]
TBA
Abstract

TBA

182017-03-14 Tue
14:20~15:20
R1203
Simeon Bird
[Johns Hopkins University]
*Special Seminar*
TBA
Abstract

TBA

192017-03-13 Mon
14:20~15:20
R1203
Baobab Liu
[ESO]
*Special Seminar*
TBA
Abstract

TBA

202017-03-09 Thu
14:20~15:20
R1203
Geoff Bower
[ASIAA]
*Special Seminar*
Localization of the Fast Radio Burst 121102
Abstract

Fast radio bursts (FRBs) are millisecond-duration, highly-dispersed radio wavelength pulses. Based on their large dispersion measure, FRBs appear to originate from extragalactic distances implying extreme luminosities that are not seen in any galactic sources. Progress in understanding FRBs has been slow because the discovered events have had >arcminute localization, making association with galaxies or galactic objects impossible. Currently, there are more theories than FRBs, which number about 20. I will describe here the first arcsecond localization of an FRB. Using the Very Large Array (VLA) and other radio telescopes, we have shown that FRB 121102 is associated with a faint persistent radio source and a faint galaxy. Gemini observations provided the redshift (z~0.2) and identification of the galaxy as a dwarf with significant star formation and low metallicity. I will discuss the implications of this discovery for our understanding of FRBs and the possibility of using FRBs to study the intergalactic medium.

212017-03-08 Wed
14:20~15:20
R1203
Xuan Fang
[University of Hong Kong]
TBA
Abstract

TBA

222017-03-07 Tue
14:20~15:20
R1203
Quan-Zhi Ye
[Caltech]
*Special Seminar*
Aging comets and their meteor showers
Abstract

Active comets lost a significant amount of volatile every time they pass through perihelion. As a result, comets will have less materials for sublimation, and one would expect that comets will continue to fade as they evolve. However, it is also suggested that the active lifetime of a comet can consists of multiple active stages separated by temporary dormant phases, making it difficult to identify true secular fading caused by aging of comets. The era of modern astronomy is unfortunately not long enough to cover the typical lifetime of a comet (usually a few hundred orbits); however, comets produce dust during their active stages, which are potentially detectable as meteor activity at the Earth. Here I discuss the effort of understanding cometary aging by examining different parts of the evolution spectrum of Jupiter-family comets (JFCs), a group of comets that dominates the cometary influx in the near-Earth space, using telescopic and meteor observations as well as dynamical investigation.

232017-03-06 Mon
14:20~15:20
R1203
Paulo Freire
[Max-Planck-Institut für Radioastronomie]
*Special Seminar*
Testing the nature of gravitational waves with observations of binary pulsars
Abstract

In this talk, I will review some of the principles of pulsar timing, and review some of the results from the timing of binary pulsars from previous work. These include the observation of gravitational waves (GWs) in the energy loss of the "Hulse-Taylor" double neutron star, almost 40 years before the LIGO observation. I then introduce ongoing work, which tests the emission of GWs with far more accuracy than in the Hulse-Taylor pulsar, and new detections of the emission of gravitational waves in pulsar-white dwarf systems, which introduce strong constraints on the nature of GWs. In particular, we are able to exclude, within observing precision, any dipolar components of gravitational radiation, showing that they are almost purely quadrupolar. These results are then used for some of the most stringent tests of general relativity and alternative theories of gravity ever accomplished.

242017-03-01 Wed
14:20~15:20
R1203
Samantha Lawler
[NRC Herzberg]
Does our Solar System Need to have Another Planet?
Abstract

The orbital element distribution of trans-Neptunian objects (TNOs) with large pericenters has been suggested to be influenced by the presence of an undetected, large planet at >200 AU from the Sun. To find additional observables caused by this scenario, we present here the first detailed emplacement simulation in the presence of a massive ninth planet on the distant Kuiper Belt. We perform 4 Gyr N-body simulations with the currently known solar system planetary architecture, plus a 10 M_earth planet with similar orbital parameters to those suggested by Trujillo & Sheppard or Batygin & Brown, and thousands of test particles in an initial planetesimal disk. We find that including a distant super-Earth-mass planet produces a substantially different orbital distribution for the scattering and detached TNOs, raising the pericenters and inclinations of moderate semimajor axis (50 < a < 500 au) objects. We test whether this signature is detectable via a simulator with the observational characteristics of four precisely characterized TNO surveys. We find that the qualitatively very distinct solar system models that include a ninth planet are essentially observationally indistinguishable from an outer solar system produced solely by the four giant planets. We also do not find any evidence for clustering of orbital angles in our simulated TNO population, and further simulations find that an additional planet causes significant changes in the orbits of known distant TNOs. Wide-field, deep surveys targeting inclined high-pericenter objects will be required to distinguish between these different scenarios.

252017-02-22 Wed
14:20~15:20
R1203
Pham Ngoc Diep
[Vietnam National Satellite Center/Vietnam Academy of Science and Technology]
Millimetre/Submillimetre Astronomy Studies of Evolved Stars, Protostars and High Redshift Galaxies
Abstract

The observation of molecular emission at millimetre and submillimetre wavelengths gives access to the study of stars having a large and cool circumstellar envelope as well as of the gas reservoirs of galaxies, in particular remote galaxies with redshift in the 2 to 5 range at the epoch of maximum star formation rate. The observation of the continuum emission underneath the molecular excitation lines provides important information on the dust content. Using Plateau de Bure and archival ALMA observations, we have been able to reconstruct in space, under simplifying hypotheses such as of invariance by rotation about an axis, both the morphology and the kinematics of such sources. Examples will illustrate these studies, including Asymptotic Giant Branch stars, protostars and gravitationally lensed high redshift galaxies.

262017-02-21 Tue
14:20~15:20
R1203
TBA
[TBA]
*Special Seminar*
TBA
Abstract

TBA

272017-02-15 Wed
14:20~15:20
R1203
Marc W. Buie
[Southwest Research Institute]
Exploring the Outer Solar System with Occultations
Abstract

The Research and Education Collaborative Occultation Network (RECON) is a project to use occultations to probe basic properties of outer solar system objects. Occultation measurements can be done with relatively small telescopes but the principle challenge is in predicting events. RECON uses a strategy of a large set of fixed sites to overcome the prediction challenge. Our system uses 28-cm telescopes with high-sensitivity integrating video cameras hosted by schools across the Western United States. Our network consists of 56 stations with an average spacing of 50 km between stations. With this system, we reduce the prediction quality needed by an order of magnitude compared to a traditional “chase-the-shadow” deployment while also probing over a 2000 km region near the body. Such data can measure the sizes and shapes of the occulting body as well as detecting very close binary systems or rings and dust environments. RECON has ofetn been described as a citizen-science project but it is really more of a new collaborative research model. This presentation will review how the project was setup and is operated and provide examples of recent scientific results from our efforts.

282017-02-08 Wed
14:20~15:20
R1203
Peter Roelfsema
[SRON]
A joint infrared space observatory - SPICA revised and upgraded
Abstract

The infrared wavelength domain allows measurements to directly assess the physical state and energy balance of cool matter in space, thus enabling the detailed study of the various processes that govern formation evolution of planets, stars and galaxies over cosmic time. Infrared space missions to date were hampered by either having a warm or a relatively small size telescope, limiting the practically achievable sensitivity. With SPICA we propose to take the next step in mid- and far-infrared research by combining a large, cold telescope with instruments employing modern ultra-sensitive detectors.
SPICA is to be launched in the late 2020s as a joint ESA-JAXA mission with instruments provided by Japanese and European consortia. The mission concept foresees a 2.5-meter diameter telescope cooled to below 8K, with the optical axis oriented perpendicularly to the axis of the spacecraft. Like on PLANCK, ‘V-grooves’ to provide passive cooling are combined with mechanical coolers to provide for an effective cryogenic system, as is needed for the cooling of the telescope assembly and the science instruments. With cooling not dependent on a cryogen the mission lifetime is expected to extend significantly beyond the required 3 years.
With the combination of low telescope background and instruments with state of the art detectors SPICA will provide spectroscopic capabilities at a uniquely high sensitivity of 2-5 x10-20 W/m2 (5σ/1hr). The instruments will offer resolutions ranging from R~50 through 3000 in the 17-230 μm domain as well as R~30.000 spectroscopy between 12 and 18 μm. Additionally the instruments will support efficient 17-35 μm broad band mapping, and small field spectroscopic imaging in the 35-230 μm range.
SPICA’s extreme spectroscopic sensitivity will give at least two orders of magnitude improvement over what has been attained to date. With this exceptional leap in performance new domains in infrared astronomy become accessible. For example, with this high sensitivity astronomers will be able to detect the [OIV] line in relatively average galaxies out to a redshift z~3. Thus, the evolution of galaxies can be followed through their most active periods in cosmic time from about 10 billion years ago to what they look like today. Also, we will be able to observe dust features from even earlier epochs, out to redshifts of z~7-8, thus providing insight into dust formation in the very early phases of the universe. Similarly, this new facility will allow us to study dust formation and evolution from very early epochs onwards, and to compare the formation history of planetary systems to that of our own solar system.

292017-01-18 Wed
14:20~15:20
1F auditorium
Dominik Riechers
[Cornell]
The Intricate Role of Cold Gas and Dust in Galaxy Evolution at Early Cosmic Epochs
Abstract

Dusty starburst galaxies at very high redshift represent an important phase in the early evolution of massive galaxies. They typically represent large-scale, gas-rich major mergers that trigger intense, short-lived bursts of star formation, which consume most of the available gas and drive the morphological transition to spheroids. At early cosmic epochs, these hyper-luminous galaxies commonly trace regions of high galaxy overdensity, and may be directly related to the formation of galaxy clusters and their giant central ellipticals. Molecular and atomic gas plays a central role in our understanding of the nature of these often heavily obscured distant systems. It represents the material that stars form out of, and its mass, distribution, excitation, and dynamics provide crucial insight into the physical processes that support the ongoing star formation and stellar mass buildup. I will discuss the most recent progress in studies of the cold gas content of dusty starburst galaxies at high redshift, back to the first billion years of cosmic time using CARMA, the Jansky Very Large Array, the Plateau de Bure interferometer, and the Atacama Large (sub)Millimeter Array (ALMA). I will also highlight our recent successful first detections of the interstellar medium in "normal" (~L*) galaxies at z>5 with ALMA, and discuss the impact of our findings on future studies back to even earlier epochs.

302017-01-11 Wed
14:20~15:20
R1203
Francesco Costagliola
[Chalmers University of Technology]
Tracing the AGN/Starburst co-evolution in compact obscured nuclei
Abstract

Observations at all redshifts suggest that the AGN and starburst evolution across cosmic time are tightly linked. The recent discovery of ubiquitous giant molecular outflows revealed that even low-luminosity AGN can have a profound impact in the evolution and star-formation history of galaxies. The compact obscured nuclei of IR-luminous galaxies have been suggested to be the ideal targets to study the early stages of the Starburst/AGN interaction. However, because of the large extinction, standard Starburst/AGN tracers cannot be used to probe the central regions of these objects and new, more sensitive methods must be developed. Here I will report some of the latest results in the study of obscured AGN/Staburst activity including observations with ALMA and the JVLA.

312017-01-10 Tue
14:20~15:20
R1203
Koju Chuang
[Leiden University]
*Special Seminar*
Formation of Complex Organics in Dark Clouds - Sweet results from the laboratory -
Abstract

Complex organic molecules (COMs) have been not only observed in hot cores of low- and high-mass protostars, but also were detected recently in cold dense clouds. Besides energetic processing of ices that were shown to produce organic species, it is interesting to understand COM formation also under dense cloud conditions, i.e., without the presence of embedded energy sources. We present our latest laboratory study of the low-temperature (15 K) solid state formation of three complex molecules – methyl formate (HC(O)OCH3), glycolaldehyde (HC(O)CH2OH) and ethylene glycol (H2C(OH)CH2OH) – through recombination of active intermediate radicals. These free radicals are formed via H-atom addition and abstraction reactions along the CO→H2CO→CH3OH hydrogenation network, which starts from CO gas accreted on the grain that successively reacts with H-atoms to form H2CO and CH3OH. The present work extends on a recent CO hydrogenation study and aims to resemble the physical-chemical conditions typical of dark molecular clouds. We confirm that H2CO, once formed by hydrogenation of CO, not only leads to CH3OH through forward addition reactions, but is also subject to backward abstractions induced by H-atoms, yielding CO again. In a similar way, H2CO is also the product of abstraction reactions of CH3OH. In this work, we show that the dominant intermediate radicals of CH3OH abstraction and H2CO addition reactions are CH2OH and CH3O, respectively. By considering both addition and abstration reactions, more reactive intermediates (HCO, CH3O and CH2OH) are produced in the ice mantle than previously thought, focussing on sequential H-atom addition reactions only. Inclusion of both types of reactions also enhances the probability to form COMs through radical-radical recombination without the need of UV photolysis or cosmic rays bombardment as external triggers. The formation of COMs realized in this way, is proven by RAIRS and TPD, also using isotopically labelled species.

322017-01-09 Mon
14:20~15:20
R1203
Erwin Lau
[Yale]
*Special Seminar*
Modeling baryonic physics in galaxy clusters
Abstract

Galaxy clusters play an important role in modern precision cosmology. As the most massive virialized objects in the universe, their abundance depends sensitively on cosmological parameters. However, uncertainties in galaxy cluster physics pose serious challenges to using forthcoming observations to make advances in cosmology with galaxy clusters. In this talk, I will highlight how we can improve our understanding of galaxy cluster physics with the state-of-the-art numerical simulations and semi-analytical modelling. In particular, I will present results from the "Omega500" simulation, a high-resolution hydrodynamic simulation suite of galaxy cluster formation that follows the evolution of dark matter and baryons in a realistic cosmological setting. I will also outline upcoming challenges in the computational modelling of major physical processes in galaxy clusters, and how we can address them in anticipation of upcoming multi-wavelength cluster surveys in the next decade.

332017-01-04 Wed
14:20~15:20
R1203
Allison Man
[ESO]
How to quench a massive galaxy?
Abstract

The progenitors of the local-day elliptical galaxies have formed the bulk of their stars in the first few Gyr of the Universe. This implies that already by z=2, there is a population of massive galaxies that have terminated their star formation somehow, and become quenched. Many plausible mechanisms have been proposed to explain early quenching in massive galaxies (e.g., active galactic nuclei feedback, halo quenching, morphological quenching). However, until recently the observations at hand are insufficient to allow us to distinguish between these mechanisms. I will review our knowledge on this topic thus far, and present efforts to tackle this decade-old question.

TEL: 886-2-3365-2200 FAX: 886-2-2367-7849
General: asiaa_replace2@_asiaa.sinica.edu.tw Media Request: epo_replace2@_asiaa.sinica.edu.tw
11F of AS/NTU Astronomy-Mathematics Building, No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan, R.O.C.