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學術活動 > 學術演講及專題研討

學術演講及專題研討 (2017)

本所學術演講每週三下午2:20~3:20邀請國內外學者報告最新天文發展,歡迎大家參與。

中研院/臺大聯合學術演講系列中,我們將邀請世界知名研究人員報告物理科學領域最新發展及長程展望。

連絡窗口: 研討會委員 (talks_replace2@_asiaa.sinica.edu.tw)

近期專題研討: 2017-03-23 Thu 14:20~15:20 [R1203]
講者:Ke-Jung Chen
講題:Lighting up the Universe with Extreme Supernovae
摘要:Recent all-sky transient searches have discovered new and unexpected explosion types that fall outside traditional SN classification schemes. These exotic outliers in many cases are due to the deaths of massive stars and therefore may have been prevalent in the primordial universe because the Pop III IMF is thought to be top-heavy. Depending on the mass of the progenitor, these outliers may be faint, magnetar-powered, pair-instability, or general relativistic instability SNe, all of which have unique observational signatures. Some of these events are superluminous, 10-100 times brighter than normal supernovae, and may produce energetic UV, X-ray, or gamma-ray bursts. Their extreme luminosities enable their detection at z > 10 and they are ideal probes of the primordial universe at cosmic dawn, prior to the advent of the first galaxies. Here, we examine these exotic explosions with state of the art 3D radiation-hydro simulations that bridge all spatial scales from the central engine to breakout into the IGM, where observational signatures can be computed. We discuss the coevolution of radiation and turbulent mixing in SN ejecta and present realistic light curves for these explosions for JWST and the coming generation of extremely large telescopes (ELTs). Detection rates for Pop III SNe can place useful constraints on the primordial IMF, and their nucleosynthetic yields can be used to study the chemical compositions of extreme metal poor stars.
近期學術演講: 2017-03-29 Wed 14:20~15:20 [R1203]
講者:Kenny Vilella
講題:What thermal convection can tell us about planetary observations: applications to Pluto and habitability of exoplanets
摘要:Thermal evolution of planetary bodies is mainly controlled by its interior thermal convection and affect importantly its atmosphere and surface processes. The observations of its direct and indirect implications provides important constraints. For instance, the polygonal network found on the nitrogen glacier Sputnik Planitia (SP) on Pluto's surface (Stern et al. 2015), indicates that thermal convection operates within SP, which in turn suggests a large glacier thickness. Thermal convection, therefore, gives information that help the interpretation of planetary observations. For instance, the thickness of SP inferred by thermal convection indicates that a deep ocean is required to explain the location of SP on the equator. Thermal convection and planetary observations are therefore closely linked.

Here I present different approaches to study thermal convection and I emphasize the important link between our work and planetary observations. First, I investigate thermal convection within SP suggested by its surface polygonal network. Based on complex 3D-numerical simulations conducted for a large range of convective system, I conclude that only internal heating may produce such a surface pattern. However, there is no clearly identified source of internal heating within SP. I propose that the surface temperature variations caused by the variation in Pluto's orbit may be an appropriate source of heating. Second, I follow a parameterized approach to predict the occurrence of partial melting in exoplanets. Partial melting being necessary to maintain an atmosphere over a long period of time, which is a prerequisite for the presence of life. I found that moderate size planets are the most likely to be habitable, which show the importance of detecting Earth-size exoplanets.
No. 時間地點 講者 題目/摘要
download PDF: 下載 PDF
12017-08-23 Wed
14:20~15:20
R1203
I-Non Chiu
[ASIAA]
TBD
摘要

TBD

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

TBD

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

TBD

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

TBD

52017-06-06 Tue
14:20~15:20
R104, CCMS
Changbom Park
[Korea Institute for Advanced Study (KIAS)]
*中研院/臺大學術討論會*
TBA
摘要

TBA

62017-06-05 Mon
14:20~15:20
R1203
Chin-Ping Hu
[The University of Hong Kong]
*專題研討*
Magnetic Field Effects on Pulsars
摘要

Pulsars are fast-rotating neutron stars with strong magnetic fields. Magnetars are an extreme group of pulsars with extraordinarily strong magnetic fields of $10^{14}$--$10^{15}$ G, and remarkable for the bursting activities and high X-ray luminosities powered by their high magnetic field. However, recent discoveries blurred the boundary between magnetars and rotation-powered pulsars (RPPs). In this talk, I will introduce the recent works on the high-magnetic-field RPPs, especially the youngest ones of J1846-0258, J1119-6127, and B1509-58. Young and high-magnetic-field RPPs have surface temperatures between the magnetars and canonical RPPs, indicating that high-magnetic-field RPPs are potential bursters and may contain toroidal magnetic fields according to the magneto-thermal evolution model. This model implies that the toroidal field could play an important role in bursting rate and the temperature anisotropic. Our recent work on the statistics of magnetars' pulse profiles agreed on this implication well. Finally, I will introduce the possible connection between the magnetars and the accreting pulsars in ultraluminous X-ray sources. Toroidal or multi-polar magnetic fields are necessary to interpret the high luminosities and the observed spin-up rates, indicating that ultraluminous pulsars are possibly powered by magnetars.

72017-05-31 Wed
14:20~15:20
R1203
Ming Sun
[University of Alabama Huntsville]
TBD
摘要

TBD

82017-05-24 Wed
14:20~15:20
R1203
Takahiro Nishimichi
[IPMU]
TBA
摘要

TBA

92017-05-17 Wed
14:20~15:20
R1203
Martin Bureau
[University of Oxford]
TBA
摘要

TBA

102017-05-10 Wed
14:20~15:20
R1203
Kevin Koay
[ASIAA]
TBD
摘要

TBD

112017-05-03 Wed
14:20~15:20
R1203
Xiaohu Li
[ASIAA]
TBA
摘要

TBA

122017-04-26 Wed
14:20~15:20
R1203
Ai-Lei Sun
[ASIAA]
TBA
摘要

TBA

132017-04-24 Mon
14:20~15:20
R1203
Jesus Toala
[ASIAA]
*專題研討*
X-ray Emission as a probe of Stellar Evolution
摘要

TBA

142017-04-19 Wed
14:20~15:20
R1203
Andrew Youdin
[University of Arizona]
TBA
摘要

TBA

152017-04-12 Wed
14:20~15:20
R1203
Hayato Shimabukuro
[Observatoire de Paris]
21cm cosmology meets artificial neural networks
摘要

The 21 cm signal from the Epoch of Reionization should be observed within the next decade. To extract from the observed data constraints on the parameters describing the underlying astrophysical processes, inversion methods must be developed. Here we test possible inversion method for EoR parameter reconstruction: artificial neural networks (ANN). We find that the quality of the parameter reconstruction depends on the sensitivity of the power spectrum to the different parameters at a given redshift, that including thermal noise and sample variance decreases the quality of the reconstruction and that using the power spectrum at several redshifts as an input to the ANN improves the quality of the reconstruction.

162017-04-06 Thu
14:20~15:20
R1203
Ellis Owen
[University College London]
*專題研討*
TBA
摘要

TBA

172017-03-31 Fri
14:20~15:20
R1203
Werner Krauth
[Ecole Normale Supérieure]
*專題研討*
Research and higher education in France, between Organizations, Schools and Universities
摘要

A mirror of the multi-faceted research environment in most countries in the world, and in particular in Europe, the French academic environment is organized by a considerable number of actors, in a way that is not totally transparent from the outside. Nevertheless, the system produces a very stable environment, and provides opportunities for research and study at the highest level of excellence. In this presentation, I will (attempt to) provide an introduction to French research organization, with a focus on my discipline, physics, and on my own institution, Ecole normale supérieure, in Paris.

182017-03-29 Wed
14:20~15:20
R1203
Kenny Vilella
[Institute of Earth Sciences, Academia Sinica]
What thermal convection can tell us about planetary observations: applications to Pluto and habitability of exoplanets
摘要

Thermal evolution of planetary bodies is mainly controlled by its interior thermal convection and affect importantly its atmosphere and surface processes. The observations of its direct and indirect implications provides important constraints. For instance, the polygonal network found on the nitrogen glacier Sputnik Planitia (SP) on Pluto's surface (Stern et al. 2015), indicates that thermal convection operates within SP, which in turn suggests a large glacier thickness. Thermal convection, therefore, gives information that help the interpretation of planetary observations. For instance, the thickness of SP inferred by thermal convection indicates that a deep ocean is required to explain the location of SP on the equator. Thermal convection and planetary observations are therefore closely linked.

Here I present different approaches to study thermal convection and I emphasize the important link between our work and planetary observations. First, I investigate thermal convection within SP suggested by its surface polygonal network. Based on complex 3D-numerical simulations conducted for a large range of convective system, I conclude that only internal heating may produce such a surface pattern. However, there is no clearly identified source of internal heating within SP. I propose that the surface temperature variations caused by the variation in Pluto's orbit may be an appropriate source of heating. Second, I follow a parameterized approach to predict the occurrence of partial melting in exoplanets. Partial melting being necessary to maintain an atmosphere over a long period of time, which is a prerequisite for the presence of life. I found that moderate size planets are the most likely to be habitable, which show the importance of detecting Earth-size exoplanets.

192017-03-24 Fri
14:20~15:20
R1203
Hyosun Kim
[ASIAA]
*專題研討*
Beloved Celestial Patterns: the Evidences of Hydrodynamic Interactions
摘要

Hydrodynamic interactions are ubiquitous. I have devoted myself in various topics related to hydrodynamic interactions encoded in the celestial patterns surrounding various astronomical objects including evolved stars, young stellar clusters, merging black hole pairs, etc. In this talk, I will show that these various phenomena have similarities and cross-connection in a theoretician's point of view and provide some potential applications and directions.

202017-03-23 Thu
14:20~15:20
R1203
Ke-Jung Chen
[NAOJ]
*專題研討*
Lighting up the Universe with Extreme Supernovae
摘要

Recent all-sky transient searches have discovered new and unexpected explosion types that fall outside traditional SN classification schemes. These exotic outliers in many cases are due to the deaths of massive stars and therefore may have been prevalent in the primordial universe because the Pop III IMF is thought to be top-heavy. Depending on the mass of the progenitor, these outliers may be faint, magnetar-powered, pair-instability, or general relativistic instability SNe, all of which have unique observational signatures. Some of these events are superluminous, 10-100 times brighter than normal supernovae, and may produce energetic UV, X-ray, or gamma-ray bursts. Their extreme luminosities enable their detection at z > 10 and they are ideal probes of the primordial universe at cosmic dawn, prior to the advent of the first galaxies. Here, we examine these exotic explosions with state of the art 3D radiation-hydro simulations that bridge all spatial scales from the central engine to breakout into the IGM, where observational signatures can be computed. We discuss the coevolution of radiation and turbulent mixing in SN ejecta and present realistic light curves for these explosions for JWST and the coming generation of extremely large telescopes (ELTs). Detection rates for Pop III SNe can place useful constraints on the primordial IMF, and their nucleosynthetic yields can be used to study the chemical compositions of extreme metal poor stars.

212017-03-22 Wed
14:20~15:20
R1203
Ziri Younsi
[University of Frankfurt]
Imaging Black Holes - Shadows, Accretion and Variability
摘要

In the coming months and years mm-VLBI observations of supermassive black holes using the Event Horizon Telescope (EHT), most notably of Saggitarius A* and M87, are expected to verify the existence of astrophysical black holes through detection and measurement of the black hole shadow. Although the mathematical description of a black hole shadow is straightforward, its observational appearance is strongly governed by the (thermo)dynamics and geometrical structure of the surrounding accretion flow. This accretion flow, particularly on event horizon-scales, is turbulent and time variable, and must be modelled using general-relativistic magnetohydrodynamical (GRMHD) simulations. The propagation of radiation and therefore the appearance of shadow images, spectra and lightcurves are calculated using GR radiation transport (GRRT). Here we combine GRMHD and GRRT calculations to derive observational predictions of what upcoming VLBI observations of Sagittarius A* are expected to observe, addressing questions concerning variability therein and also discussing the possibility of testing the Kerr black hole hypothesis and constraining other black hole solutions and theories of gravity.

222017-03-20 Mon
14:20~15:20
R1203
Andrew Mann
[University of Texas at Austin]
*專題研討*
Tracing Planetary Evolution from Formation to Maturity
摘要

Planets are not born in their final state; rather, they change significantly over their lifetimes. Understanding how planets evolve has been a central question since the discovery of the first exoplanets. The first few hundred million years are thought to be the most formative, but planets in this age range are also the most difficult to identify and characterize. Instead, research has focused on inferring the history of planets through patterns in the population of older systems. In this talk I will discuss how this paradigm is shifting, as novel search techniques and new missions have enabled our discovery of Earth- to Jupuiter-size planets as young as 10 Myr. These discoveries have altered our understanding of how planets migrate and lose atmosphere, but raise further questions about the physical drivers of these changes. The upcoming TESS mission will discover hundreds more young planets, including analogues of a young Earth. Combined with follow-up from new NIR spectrographs (e.g., SPIRou on CFHT, IRD on Subaru), the TESS sample will enable new tests of planet formation and evolution through population statistics. Eventually, JWST, SPICA, and 30m-class telescopes can be used to study the atmospheres of young, rocky planets, providing unique insight into the history of potentially habitable planets.

232017-03-16 Thu
14:20~15:20
R1203
Toshiya Namikawa
[Stanford University]
*專題研討*
Cosmology with cosmic microwave background polarization
摘要

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.

242017-03-15 Wed
14:20~15:20
R1203
Sofia Wallstrom
[ASIAA]
The death throes of massive stars
摘要

Massive evolved stars affect their local surroundings as they go through phases of intense mass-loss and eventually explode as supernovae, adding kinetic energy and freshly synthesised material to the interstellar medium. Over time, these processes affect the chemical evolution of the interstellar medium on a galactic scale. I will here present my PhD research, which probed the death throes of massive stars at various stages. First, CO observations were used to study the circumstellar environment of a massive star, the yellow hypergiant IRAS 17163-3907. Observations with APEX and ALMA ACA reveal a complex environment with several distinct components: a fast recent stellar wind of 100 km/s, a clumpy CO ring which appears to be a torus ejected by the star several thousand years ago, and a unidirectional bright spur extending from the star to the clumpy ring. These asymmetries are not seen in infrared dust observations, and demonstrate the complexity of massive evolved stars and the need for high resolution molecular observations to understand them. Next, observations of CO lines in the supernova remnant Cassiopeia A were used to study the effect of the reverse shock on supernova ejecta. A large column density of warm CO was found, which has most likely re-formed after the passage of the reverse shock. The high temperature and density implies that thermal conduction by electrons may be an important process for the evolution of dense ejecta knots, with implications for the survival of supernova dust. Finally, the contribution of massive stars to galactic chemical enrichment was investigated indirectly with measurements of isotopic ratios in a molecular absorber at z=0.68 towards B0218-211. The ratios at z=0.68 were found to be very different from those in the solar neighborhood, but similar to the ratios found in another absorber at z=0.89 and in starburst galaxies. The interpretation of these ratios is as a signature of enrichment mainly by massive stars.

252017-03-14 Tue
14:20~15:20
R1203
Simeon Bird
[Johns Hopkins University]
*專題研討*
Simulating Neutral Hydrogen, Galaxy Clusters and Primordial Black Holes
摘要

It has recently become possible to perform large-scale cosmological simulations incorporating gas and enough physical processes to roughly reproduce the distribution of matter observed in the Universe. Our simulations have allowed us to resolve several long-standing problems in astrophysics, as well as suggesting new lines of investigation. I will describe in particular my work on the distribution of neutral hydrogen absorbers and galaxy clusters, both of which have implications for cosmology. I will then discuss my recent work on the implications of the LIGO gravitational wave detection for primordial black holes, which raises the exciting possibility that LIGO may have detected the dark matter.

262017-03-13 Mon
14:20~15:20
R1203
Baobab Liu
[ESO]
*專題研討*
Star formation: previous developments and future
摘要

Limited by the coarse angular resolutions and/or the poor sensitivities of the previous generation (sub)millimeter telescopes (SMT, CSO, IRAM, SMA, Herschel, Planck), significant efforts and resources have been devoted to improving the constraints on a few "macro phenomenological correlations", such as the star-formation (e.g., Kennicutt-Schmidt law), Larson's laws, etc. While these laws are almost treated as fundamental physics laws, and have been routinely compared with any new observational measurements, the micro physics including how the stellar cluster-formation is related to an interplay between the supersonic gas motions and self-gravitational contractions, remain poorly understood. As an example, the meaning of the term "turbulence" has been rather ambiguous for the community of star-formation. In this talk, I will present our preliminary developments about how images of molecular cloud structures with extremely high spatial and intensity dynamic ranges may enable discriminating a variety of physical conditions, and how such developments can be prosecuted with the facilities of Taiwan and EAO.

272017-03-09 Thu
14:20~15:20
R1203
Geoff Bower
[ASIAA]
*專題研討*
Localization of the Fast Radio Burst 121102
摘要

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.

282017-03-08 Wed
14:20~15:20
R1203
Xuan Fang
[University of Hong Kong]
Peering into the Halo of the Andromeda Galaxy Using Planetary Nebulae
摘要

It has been widely accepted that in hierarchical cosmology, a large galaxy evolves through accretion/merging of smaller galaxies. The effects of such galaxy interaction are imprinted in the outer disk or halo of a galaxy in the form of stellar condensations (i.e., substructures) like tidal streams. As the nearest large spiral system, the Andromeda Galaxy (M31) is an excellent candidate to study galaxy interaction and evolution. In order to study the halo and substructures of M31 using planetary nebulae (PNe) as tracers of chemistry and kinematics, we carried out very deep spectroscopic observations of a carefully selected sample of PNe using the 10.4m Gran Telescopio Canarias (GTC, La Palma). The target PNe are located in different regions: the substructures (the Northern Spur and the Giant Stream), the outer halo (or the exodisk) of M31, and M32. Our chemical study reveals: 1) the halo PNe, as far as ~180 kpc from galactic center, have oxygen abundances close to the solar value, supporting the current view that the external regions of M31 are the result of complex interaction and merger process; and 2) the substructure PNe have lower oxygen abundances, indicating a different origin.

292017-03-07 Tue
14:20~15:20
R1203
Quan-Zhi Ye
[Caltech]
*專題研討*
Aging comets and their meteor showers
摘要

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.

302017-03-06 Mon
14:20~15:20
R1203
Paulo Freire
[Max-Planck-Institut für Radioastronomie]
*專題研討*
Testing the nature of gravitational waves with observations of binary pulsars
摘要

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.

312017-03-01 Wed
14:20~15:20
R1203
Samantha Lawler
[NRC Herzberg]
Does our Solar System Need to have Another Planet?
摘要

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.

322017-02-22 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
摘要

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.

332017-02-21 Tue
14:20~15:20
R1203
TBA
[TBA]
*專題研討*
TBA
摘要

TBA

342017-02-15 Wed
14:20~15:20
R1203
Marc W. Buie
[Southwest Research Institute]
Exploring the Outer Solar System with Occultations
摘要

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.

352017-02-08 Wed
14:20~15:20
R1203
Peter Roelfsema
[SRON]
A joint infrared space observatory - SPICA revised and upgraded
摘要

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.

362017-01-18 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
摘要

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.

372017-01-11 Wed
14:20~15:20
R1203
Francesco Costagliola
[Chalmers University of Technology]
Tracing the AGN/Starburst co-evolution in compact obscured nuclei
摘要

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.

382017-01-10 Tue
14:20~15:20
R1203
Koju Chuang
[Leiden University]
*專題研討*
Formation of Complex Organics in Dark Clouds - Sweet results from the laboratory -
摘要

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.

392017-01-09 Mon
14:20~15:20
R1203
Erwin Lau
[Yale]
*專題研討*
Modeling baryonic physics in galaxy clusters
摘要

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.

402017-01-04 Wed
14:20~15:20
R1203
Allison Man
[ESO]
How to quench a massive galaxy?
摘要

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.

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台北市10617羅斯福路四段1號 中央研究院/台灣大學天文數學館11樓