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Activity > Colloquium

Colloquium (2015)

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
12015-12-29 Tue
14:20~15:20
Physics 104
Ue-Li Pen
[Canadian Institute for Theoretical Astrophysics, University of Toronto]
*ASIAA/NTU Joint Colloquium*
Past, present and future of Fast Radio Bursts: the brightest events in the universe since the big bang
Abstract

I report on recent progress to understand the nature of fast radio bursts. Most properties are inferred through propagation effects, including dispersion, scattering, scintillation, and rotation measure. I will review the issues, survey some of the proposed candidates ranging from terrestrial to cosmological, and conclude with prospects for the near future.

22015-12-17 Thu
14:20~15:20
R1203
Sperello di Serego Alighieri
[INAF - Osservatorio Astrofisico di Arcetri]
*Special Seminar*
Dust in Early-Type Galaxies
Abstract

Dust is an important component of the multi-phase interstellar medium of Early-Type Galaxies (ETG) and can give important clues on the origin and evolution of ETG. After an introduction to the subject I will show and discuss recent results obtained on the dust content of a complete sample of 910 ETG in the Virgo cluster with the Herschel satellite and on a comparison of these data with those obtained on a similar sample of H-ATLAS/GAMA ETG in low density environment.

32015-12-16 Wed
14:20~15:20
R1203
Stefan Hilbert
[Ludwig-Maximilians-Universität München]
Linking Gravitational Lensing Observations and Theory with Simulations
Abstract

Gravitational lensing effects allow us to study the the large-scale geometry and matter distribution of our Universe, and thereby can provide unique insights into, e.g., the nature of dark energy, dark matter, and their connection to the luminous matter. Numerical simulations are essential for the quantitative interpretation of gravitational lensing observations and for extracting accurate constraints for physical models of galaxies, the large-scale structure, and our whole Universe. I discuss several applications of numerical simulations to better understand strong and weak gravitational lensing observations for cosmology.

42015-12-09 Wed
14:20~15:20
R1203
Anne Dutrey
[Laboratoire d'Astrophysique de Bordeaux]
GG Tau: The Ringworld and Beyond Mass Accretion and Planetary Formation in Young Multiple Stellar Systems
Abstract

In binary stellar systems, exoplanet searches have revealed planetary mass companions orbiting both in circumstellar and in circumbinary orbits. HD simulations and observations reveal that circumstellar and circumbinary disks may exhibit different physical conditions for planet formation. Although binaries and higher order multiple stars are relatively common in nearby star forming regions, surprisingly few systems with circumbinary distributions of proto-planetary material have been found. GG Tau A is one of these systems, it has a spectacular ring of dust and gas encircling its central triple star has become a unique laboratory for investigating the physics of circumsystem gas and dust evolution. I review in this talk its physical properties in light of mass accretion and possible planet formation.

52015-12-08 Tue
14:20~15:20
R1203
Frank Shu
[ASIAA]
Astrophysics of Molten Salt Breeder Reactors: Building a Nuclear Reactor Better than the Sun (conclusion)
Abstract

Climate change is real, here, and potentially catastrophic in its effect. We argue that the scale of the transformation needed to mitigate climate change requires breakthroughs in current technologies, most importantly, in new forms of fission reactors that are (1) safe in their inherent design, (2) sustainable in terms of meeting future energy demand for several centuries as well as having an acceptable solution for nuclear waste disposal, (3) secure in terms of weapons proliferation, (4) superior in competitive cost relative to other alternatives. We focus on one design – a two-fluid molten salt breeder reactor that uses the thorium fuel cycle – that has all four attributes, as well as a pathway to convert smoothly from our current unsustainable dependence on light-water reactors that use the once-through uranium fuel cycle. We argue how a spherical reactor can be understood in terms of astrophysical principles that govern the equation of state of the matter, mechanical structure, energy generation (with fission replacing fusion), and heat transport inside stars. An important difference is that engineering solutions can avoid evolution away from the so-called zero-age main-sequence. A subtext of the talk is that astrophysicists with a training in systems-thinking can bring unique technical insights to the challenges of climate-change mitigation and energy transformation. However, we also need to appreciate that the needed changes from business as usual are not only in scientific approach, but must deal with economic, political, and social realities. Climate change is a problem that affects all segments of society, and it cannot be solved without the cooperation of important stakeholders, in particular, the current suppliers of world primary energy (in descending order of market share in 2012): fossil fuels (81.7%), biofuels (10.0%), nuclear power (4.8%), hydropower (2.4%), and wind/solar/geothermal (1.1%).

62015-12-07 Mon
09:30~10:30
R1203
Stephane Guilloteau
[Laboratoire d'Astrophysique de Bordeaux]
*Special Seminar*
Fast imaging with ALMA : from CASA to GILDAS
Abstract

The ALMA interferrometer uses the CASA software for calibration and imaging. While calibration can only be done with CASA, other softwares can be used for imaging. This can be convenient as CASA is rather slow. Exporting data from CASA is however non trivial, and requires some understanding of the differences between the data model used in CASA and the destination software. I will show how to transfer calibrated ALMA data from CASA to GILDAS, and illustrate the capacities of GILDAS to handle efficiently large data set. I will show how to efficiently use the fast visualisation and deconvolution tools of Mapping, as well as the spectral line analysis tools available in CLASS (natively of through the Python Weeds plug-in).

72015-12-02 Wed
14:20~15:20
R1203
Teppei Okumura
[Kavli IPMU]
Observational and theoretical studies of large-scale structure of the Universe using galaxy redshift surveys
Abstract

Probing the nature of dark energy, which drives the acceleration of the cosmic expansion, is one of the most important issues in cosmology. The large-scale structure of the Universe, which can be traced by a galaxy survey, is considered as one of the most powerful cosmological tools for such a purpose because one can obtain 3-dimensional matter distribution, while CMB probes the 2-d projection along the line of sight. In this talk, first I will present current observational constraints on dark energy properties from galaxy surveys, focusing on baryon acoustic oscillations and redshift-space distortions. Next I will show some issues which occur when one tries to extract cosmological information from galaxy surveys, which implies necessity to develop more accurate theoretical templates for the galaxy clustering. Then I will present a new theoretical formalism I have been developing to predict the galaxy clustering in redshift space. Finally, I will address how such a theoretical formalism with high precision becomes critically important when one wants to apply it for future, precision galaxy surveys, such as the Subaru PFS survey.

82015-12-01 Tue
14:20~15:20
1203
Frank Shu
[ASIAA]
Astrophysics of Molten Salt Breeder Reactors: Building a Nuclear Reactor Better than the Sun
Abstract

Climate change is real, here, and potentially catastrophic in its effect. We argue that the scale of the transformation needed to mitigate climate change requires breakthroughs in current technologies, most importantly, in new forms of fission reactors that are (1) safe in their inherent design, (2) sustainable in terms of meeting future energy demand for several centuries as well as having an acceptable solution for nuclear waste disposal, (3) secure in terms of weapons proliferation, (4) superior in competitive cost relative to other alternatives. We focus on one design – a two-fluid molten salt breeder reactor that uses the thorium fuel cycle – that has all four attributes, as well as a pathway to convert smoothly from our current unsustainable dependence on light-water reactors that use the once-through uranium fuel cycle. We argue how a spherical reactor can be understood in terms of astrophysical principles that govern the equation of state of the matter, mechanical structure, energy generation (with fission replacing fusion), and heat transport inside stars. An important difference is that engineering solutions can avoid evolution away from the so-called zero-age main-sequence. A subtext of the talk is that astrophysicists with a training in systems-thinking can bring unique technical insights to the challenges of climate-change mitigation and energy transformation. However, we also need to appreciate that the needed changes from business as usual are not only in scientific approach, but must deal with economic, political, and social realities. Climate change is a problem that affects all segments of society, and it cannot be solved without the cooperation of important stakeholders, in particular, the current suppliers of world primary energy (in descending order of market share in 2012): fossil fuels (81.7%), biofuels (10.0%), nuclear power (4.8%), hydropower (2.4%), and wind/solar/geothermal (1.1%).

92015-11-30 Mon
14:20~15:20
R1203
Qing-Zhu Yin
[University of California Davis]
*Special Seminar*
Planetary Genealogy, Volatile Element Depletion and Timescale of Planet Formation: Power of Isotopes as Tracers for the Birth of Solar System
Abstract

In this talk, I will show some examples of using isotopes (measured in meteorites) as emerging new tools to study the origin of our solar system, to gauge the environment of its birth and the heterogeneous nature of the protoplanetary disk, and how we date (constrain the timing of) some of the major processes of planetary formation. Specifically, I will show (1) how some isotopic signatures now allow us to trace “genealogy” of planetary materials we have in hand; (2) how some isotope signatures might be correlated to heliocentric distances of planetary materials; (3) how a major process such as volatile element depletion experienced by the early solar system could be dated with proper selection of radiometric tools.

102015-11-25 Wed
14:20~15:20
R1203
Bing-Ming Chen
[National Synchrotron Center of Taiwan]
Looking into Space with Far-UV Spectroscopy and Photochemistry
Abstract

Far-UV (FUV) spectroscopies and photochemical processes of interstellar molecules attract interest because the information yields detailed knowledge about chemical transformations in extraterrestrial environments. Synchrotron radiation (SR) provides an intense and continuous source of FUV light. The high quality of FUV from SR gives the chances for scientists to investigate the spectroscopy and photochemistry of interstellar molecule in this region. Using the FUV beam lines from the 1.5 GeV storage ring at National Synchrotron Radiation Research Center (NSRRC) in Taiwan, we are currently conducting the experiments of photoabsorption, photodissociation, and photoluminescence researches applied to astro-science. Taking the advantage of synchrotron, we explore the FUV astro-science with exciting prospects. For example, to understand the atmosphere and climate of an extraterrestrial body and their variation, a key issue is the extent of isotopic fractionation, such as D/H. A mechanism proposed to explain variations in isotopic fractionation on planets is called the photo-induced fractionation effect (PHIFE). The crucial idea is that the rate of photolysis differs greatly for various isotopomers/isotopologues near the absorption threshold region. To assess the potential for photochemically induced changes in stellar and upper atmosphere, we thus study the FUV absolute absorption cross sections of pertinent planetary species and their isotopomers/isotopologues. These FUV data are keys to understand the extent of isotopic fractionations in our planets. Other examples of FUV astro-science will also be discussed in the presentation.

112015-11-24 Tue
14:20~15:20
Physics 104
Olivier Doré
[JPL/Caltech]
*ASIAA/NTU Joint Colloquium*
From Planck to SPHEREx: Adding the 3rd Dimension to a Full-sky Map to Probe Inflation
Abstract

The Planck success leaves cosmology with impressively well established questions and... few answers. Amongst them, the nature of the initial conditions that led to the large-scale structure we observe today is one of the most salient. I will briefly review Planck latest results, and motivate the need for the 3D mapping of an ultra-large volume to directly observe the nature of inflation. From a theoretical point of view, measuring the largest scales promises a powerful and clean probe of the initial conditions. The modeling of these large scales yields interesting (solvable) physics problems. The measurement of these large scales is also feasible: I will present a proposed satellite mission, SPHEREx, that promises to accomplish such a mapping, and much more. By constructing the first all-sky near-infrared spectral survey, SPHEREx will not only constrain the physics of inflation with unprecedented accuracy but also offer new insights on the origin and history of galaxies and build a spectral catalog of 100s of millions of objects for the astronomy community to use.

122015-11-23 Mon
14:20~15:20
R1203
Joseph Mohr
[Ludwig-Maximilians-Universität München]
Studies of Galaxy Clusters and Cosmology with the South Pole Telescope and the Dark Energy Survey
Abstract

The South Pole Telescope survey of 2500 deg^2 in the southern sky has enabled the selection of a large sample of massive galaxy clusters extending to z~1.5 through their Sunyaev-Zel'dovich effect. Dark Energy Survey deep, optical multiband imaging is enabling studies of the galaxy populations within those clusters and constraints on the masses of the systems through weak lensing. Analyses of the population of SZE selected clusters from SPT indicates cosmological constraints that are in good agreement with other cosmological probes and that together with other probes provide among the most precise constraints yet on the growth rate of cosmic structure and the equation of state of the dark energy. Improved mass constraints from weak lensing and new cluster finding experiments in the X-ray through eROSITA promise to open the window on new studies of cosmology and structure evolution.

132015-11-19 Thu
14:20~15:20
R1203
Olivier Doré
[JPL/Caltech]
*Special Seminar*
SPHEREx: Building a An All-Sky Spectral Survey
Abstract

SPHEREx, a mission in NASA's Small Explorer (SMEX) program that was selected for Phase A in July 2015, is an all-sky survey satellite designed to address all three science goals in NASA's astrophysics division: probe the origin and destiny of our Universe; explore whether planets around other stars could harbor life; and explore the origin and evolution of galaxies. These themes are addressed by a single survey, with a single instrument. I will describe how SPHEREx can probe the physics of inflationary non-Gaussianity by measuring large-scale structure with galaxy redshifts over a large cosmological volume at low redshifts, complementing high-redshift surveys optimized to constrain dark energy. SPHEREx will be the first all-sky near-infrared spectral survey, creating a legacy archive of spectra. In particular, it will measure the redshifts of over 500 million galaxies of all types, an unprecedented dataset. Using this catalog, SPHEREx will reduce the uncertainty in fNL -- a parameter describing the inflationary initial conditions -- by a factor of more than 10 compared with CMB measurements. At the same time, this catalog will enable strong scientific synergies with Euclid and WFIRST.

142015-11-18 Wed
14:20~15:20
R1203
Dmitry Semenov
[Max Planck Institute for Astronomy]
Molecules as probes of physics of the ISM and protoplanetary disks
Abstract

Molecular lines provide powerful diagnostics of thermal, density and kinematics structure of gas in various astrophysical environments. To assess this wealth of information, however, one has to understand how formation and destruction of molecules in space proceed, and how molecular lines are excited. In my review talk I'll first summarize our current understanding of these processes. Then, I'll highlight a few interesting cases how chemical modeling and analysis can help astronomers to probe temperatures, densities, and evolutionary phases in the regions of low- and high-mass star formation and protoplanetary disks. These will include synthesis of complex organic molecules and deuterium fractionation in infrared dark clouds (IRDCs) and Hot Cores as well as in prestellar cores and protoplanetary disks. A particular emphasis will be put to discuss a possible origin of Earth's water and carbon matter.

152015-11-11 Wed
14:20~15:20
R1203
Bruna Vajgel
[National Observatory, Rio de Janeiro]
Multiwavelength Study Of Galaxy Groups In The Boötes Region
Abstract

According to the hierarchical model of large scale structure formation, galaxy groups are the building blocks of galaxy clusters. Also, approximately 80% of the galaxies in the local universe reside in groups and clusters. For these two reasons galaxy groups are important for understanding the formation and evolution of clusters and the influence of environment on the evolution of galaxies. Here I will present the results of my Ph.D. thesis, in which I performed a comparison between galaxy groups and clusters in the Boötes region in order to understand the similarities and differences between the two types of systems. I will conclude my talk by presenting an overview of my current project that is based on a collaboration between ON, Leiden Observatory and ASIAA. This project is aimed at studying AGN and galaxy groups in Boötes by combining data from Chandra and Spitzer with new data from Subaru in the optical and LOFAR in the radio.

162015-11-05 Thu
14:20~15:20
R1203
Jennifer Lotz
[STScI]
The Frontier Fields
Abstract

Exceptionally deep observations of the distant universe with the Hubble Space Telescope have consistently pushed the frontiers of human knowledge. How deep can we go? What are the faintest and most distant galaxies we can see with the Hubble Space Telescope now, before the launch of the James Webb Space Telescope? This is the challenge taken up by the Frontier Fields, a director's discretionary time campaign with HST and the Spitzer Space Telescope to see deeper into the universe than ever before. The Frontier Fields combines the power of HST with the natural gravitational telescopes of high-magnification clusters of galaxies to produce the deepest observations of clusters and their lensed galaxies ever obtained. I will review the original goals of the Frontier Fields program and its progress over the last several years. In addition to pushing forward the study of the most distant galaxies, the Frontier Fields have been transformative in the study of galaxy clusters and their lensing properties. Finally, I will discuss the prospects for studying galaxies at cosmic dawn with JWST, extremely large ground-based telescopes, and future space missions over the next decade and beyond.

172015-10-21 Wed
14:20~15:20
R1203
Tommaso Treu
[UCLA]
The Grism Lens-Amplified Survey from Space (GLASS): Dissecting reionization, z~2 galaxies, and dense environments
Abstract

The Grism Lens-Amplified Survey from Space (GLASS) is a large HST cycle-21 program targeting 10 massive galaxy clusters with extensive HST imaging from CLASH and the Frontier Field Initiative. The program consists of 140 primary and 140 parallel orbits of near-infrared WCF3 and optical ACS grism observations, which result in spatially resolved spectroscopy of thousands of galaxies. GLASS has three primary science drivers although a wide variety of other science investigations are possible with the public GLASS data (e.g. SN 'Refsdal'). The key science goals of GLASS are to: 1) shed light on the epoch of reionization, by measuring the lyman alpha optical depth at z>6; 2) Study gas accretion, star formation, and outflows by spatially mapping resolved star formation and determine metallicity gradients from emission lines of galaxies at 1.3

182015-10-20 Tue
14:20~15:20
Physics 104
Tommaso Treu
[UCLA]
*ASIAA/NTU Joint Colloquium*
What's the universe made of?
Abstract

What is the nature of dark energy and dark matter? I will describe two astronomical experiments based on strong gravitational lensing that can address this question in a novel way. In the first experiment, strong gravitational lenses where the background source is variable in time and the foreground deflector is a massive galaxy are used as cosmic "standard rods". I will illustrate recent advances in modelling techniques and data quality that enable a 6-7% measurement of constraints on distance from a single gravitational lens. I will show that results from just two systems yield constraints on the equation of state of dark energy and flatness comparable to those obtained with the best probes. The second experiment uses the flux ratios between multiple images of gravitationally lensed quasars to detect the presence of dark subhalos independent of their stellar content. This tests a fundamental prediction of the cold dark matter model, i.e. that galaxies should be surrounded by large numbers of dark satellite subhalos. Proof that such satellites do not exist would force a revision of the model in favor of more exotic alternatives like warm dark matter. I will show first results from this experiment based on Keck-Adaptive Optics observations. I will then conclude by discussing the bright prospects of studies of the dark sector using gravitational lensing.

192015-10-19 Mon
14:20~15:20
physics 104
Pierre Cox
[ALMA observatory]
*ASIAA/NTU Joint Colloquium*
Atacama Large Millimeter/submillimeter Array (ALMA): Status and Development
Abstract

The Atacama Large Millimeter/submillimeter Array (ALMA) is an aperture synthesis interferometer that currently operates from wavelengths of 3 mm to 350 microns with up to sixty six (66) array elements: fifty four (54) of 12-m diameter and twelve (12) of 7-m diameter. The array is located at the ALMA Array Operations Site (AOS) on the Chajnator plateau (at an altitude of about 5000 meters) in the Atacama desert in northern Chile. While the antennas and most of the hardware for the receivers are on site, array capabilities are still expanding and the observatory is ramping up towards full operations. Early science observations have been ongoing since October 2011 and ALMA started the fourth cycle of Early Science observations. Many exciting, fundamental results have already been obtained. I will review the current status of the project, the array performance, testing, and development projects and present a selection of some of the most exciting scientific results from the solar system to the early universe. In short, I will present ALMA: past, present and future.

202015-10-15 Thu
14:20~15:20
R1203
Ming-yi Lin
[MPE]
*Special Seminar*
Thick Disks of Dense Gas around the Nuclei of Nearby Seyfert Galaxies
Abstract

We will present the dense molecular gas in the central regions of nearby Seyfert galaxies, focusing on the HCN(1-0) and HCO+(1-0) molecules which have been observed by Plateau de Bure Interferometer (PdBI). In one remarkable case, NGC 3079, we will discuss the origins and implications for the double blue-shifted absorption lines. We combine our new data with similar observations in the literature to create a sample of 8 Seyferts with comparable data. In 7 of these, the emission line kinematics implies thick disk structures of 50-100pc scales, suggesting such structures are a common occurrence. We find a relation between the circumnuclear HCN luminosity and dynamical mass that can be explained by a gas fraction of ~10% and a conversion factor of ~10. Adopting a different perspective to probe the physical properties of the gas close around AGN, we report on an analysis of molecular line ratios which indicates that the clouds in this region are not self-gravitating. Finally (if it still has time), we will briefly introduce the current status of Swift-BAT AGN large program.

212015-10-07 Wed
14:20~15:20
R1203
Mark Thiemens
[UCSD]
The source of meteorite oxygen isotopic anomalies in meteorites
222015-09-30 Wed
14:20~15:20
R1203
Michael Busch
[SETI Institute]
Radar Astronomy and Near-Earth Asteroids
Abstract

The near-Earth asteroids (NEAs) are a population of objects on orbits around the Sun that pass near or cross that of Earth. They are probes of solar system history, accessible targets for spacecraft missions, and a potential hazard to life on Earth. Ground-based radar observations with large radio telescopes provide the extremely accurate astrometry and trajectory predictions for near-Earth asteroids. They also provide detailed information on the shapes, spin states, and surface properties of a large number of objects; giving essential context for spacecraft missions to asteroids. I will describe the techniques of planetary radar astronomy and review the capabilities of radar observations from the Arecibo Observatory, the Goldstone Deep Space Network site, the Green Bank Telescope, and the Very Long Baseline Array. Then I will detail the physical properties of a few asteroid radar targets; including Toutatis, visited by the Chang'e 2 spacecraft in 2012, and Bennu, target of NASA's upcoming OSIRIS-REx mission.

232015-09-24 Thu
14:20~15:20
R1203
Jonathan Sievers
[University of KwaZulu‑Natal]
*Special Seminar*
HIRAX and the Search for Fast Radio Bursts
Abstract

The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a proposed array of 1024 cheap 6m dishes that has received preliminary approval from the South African NRF. The main goals of HIRAX include measurements of Baryon Acoustic Oscillations at redshift 0.8-2.5, searching for new pulsars and radio transients, and discovery of new neutral hydrogen absorbers. Preparations for HIRAX include the development of a new pipeline to search for Fast Radio Bursts (FRBs), which are some of the most enigmatic things in the sky. They burst incredibly brightly (~10 Jy) for a millisecond, never to be seen again, and their origin and even distance (and hence energy scale) is completely unknown. We have run the trial pipeline on 650 hours of suitable GBT data looking for FRBs. We present an overview of HIRAX and preliminary results from the FRB search.

242015-09-23 Wed
14:20~15:20
R1203
Cynthia Chiang
[University of KwaZulu‑Natal]
Searching for the Echoes of Inflation with SPIDER
Abstract

The cosmic microwave background (CMB) is a powerful tool for cosmology, encoding a wealth of information about the universe's history and structure. In particular, precision CMB polarimetry has long held the promise of revealing the physics of inflation through a minuscule "B-mode" imprint that is imparted by primordial gravitational waves. I will discuss our current knowledge of CMB polarization, and I will describe a new instrument, SPIDER, that aims to characterize the inflationary B-mode signal with high sensitivity and fidelity. SPIDER is a balloon-borne telescope that launched from McMurdo Station, Antarctica on January 1, 2015, and successfully observed for 16 days. I will discuss the preliminary in-flight performance and prospects for the science analysis.

252015-09-16 Wed
14:20~15:20
R1203
Brett Gladman
[University of British Columbia]
Resonant Kuiper Belt Objects
Abstract

Orbital resonances play a major role in the distribution of small bodies in our Solar System, and almost certainly in other planetary systems. They sometimes serve as traps, and in other situations are a rapid source of instability. This talk will present a primer on orbital resonances and then discuss the resonant populations present in our Kuiper belt. The resonance dynamics in the Kuiper belt is complex but is yielding its secrets to careful survey work, like the Outer Solar System Origins Survey (OSSOS) running on CFHT via a joint Canada+France+Taiwan team. Some of the selection effects in outer Solar System surveys will be illustrated, which need to be understood for projects like LSST. The early Solar System processes which created these resonant populations will be outlined, providing a window into planetary formation and evolution.

262015-09-14 Mon
14:20~15:20
R1203
Kevin Heng
[University of Bern]
Exoplanetary Atmospheres in Eras
Abstract

The observational scrutiny of the atmospheres of exoplanets is now a legitimate field of inquiry, which has motivated their theoretical study. In this review talk, I will summarise and highlight the state of the art of both observations and theory of exoplanetary atmospheres. The review is organised into eras, starting from the birth of spectrophotometry to the upcoming set of next-generation exoplanet hunters and characterisers. On the observational side, I will review spectrophotometry, phase curves, eclipse mapping, direct imaging and ultra-high-resolution spectroscopy. On the theoretical side, I will review atmospheric radiation, chemistry and circulation (fluid dynamics). I will discuss the problem of bright stars and why we need the next-generation of exoplanet hunting machines (CHEOPS, TESS and PLATO) to build up a better target list for atmospheric characterisation. Finally, there will be a discussion of the habitable zone and also how the conversations between the scientists from different sub-disciplines need to be more constructive.

272015-09-09 Wed
14:20~15:20
R1203
Hsi-Yu Schive
[NTU]
ΨDM vs. CDM: from Local Dwarf Galaxies to High-z Luminosity Functions
Abstract

The newly established luminosity functions (LFs) of high-z galaxies at z ~ 4 - 10 can provide a stringent check on dark matter models that aim to explain the core properties of dwarf galaxies. The cores of dwarf spheroidal galaxies are understood to be too large to be accounted for by free streaming of warm dark matter without overly suppressing the formation of such galaxies. In this talk, I will show from cosmological simulations that wave dark matter, ΨDM, appropriate for light bosons such as axions, does not suffer this problem, given a boson mass of m ~ 10^{-22} eV. The large-scale structure of ΨDM is indistinguishable from cold dark matter (CDM), as desired, but differs radically inside galaxies where quantum interference forms solitonic cores surrounded by extended halos of fluctuating density granules. The halo mass function is suppressed below ~ 10^10 M⊙ at a level that is consistent with the observed high-z LFs and the Thomson optical depth recently reported by Planck. Moreover, ΨDM predicts that the LFs should turn over slowly around an intrinsic UV luminosity of M_UV ≥ -16 at z ≥ 4, distinctly different from CDM. We also show that for galaxies magnified >10x in the Hubble Frontier Fields, ΨDM predicts an order of magnitude fewer detections than CDM at z ~ 10 down to M_UV ~ -15, allowing us to distinguish between these very different interpretations for the observed coldness of dark matter.

282015-09-02 Wed
14:20~15:20
R1203
Edward Tong
[SAO]
Next Generation Receiver System for the SMA
Abstract

During the past few years, the SMA has been engaging in a wideband receiver upgrade. Front‐end receivers with IF bandwidth of 12+ GHz have been introduced. Most of these receivers employ series distributed SIS mixers fabricated in ASIAA. Later this year, we will be introducing a new set of receivers that cover 210‐270 GHz, which can be operated together with the existing 200 or 300 GHz receiver sets. At the same time, a new digital backend, the SWARM correlator, is being developed and put into action. Powered by the 5 GSample/sec Analog‐Digital Convertor developed by ASIAA, SWARM currently offers 2 x 1.5 GHz bandwidth, in addition to the 2 x 2 GHz provided by the ASIC (or legacy) correlator. This wideband receiver upgrade has improved the sensitivity of the SMA. Under good weather conditions, the SMA can deliver a detection threshold of 1 mJy or better at 345 GHz with the ASIC correlator alone. Further gains are being materialized when the SWARM data is included. Looking beyond the current phase of receiver upgrade, we believe that the sensitivity of the SMA can see further improvements. Our vision for the Next Generation Receiver System for the SMA includes a combination of re‐formulation of the front‐end hardware, coupled with a continued expansion of the backend digital hardware. In order to achieve this objective, the entire receiver system has to be overhauled. We are drawing up plans to achieve this, with the aim of targeting specific areas of science that the SMA is best positioned to do well. We will present our plans, and we hope to get inputs from both the technical and scientific groups in ASIAA, which have strong interests in the continued operation of the SMA.

292015-09-01 Tue
14:20~15:20
R1203
S. K. Pan
[NRAO]
*Special Seminar*
The CDL's current status and future plans
Abstract

An overview of the current status of the NRAO Central Development Laboratory will be presented. Future development plans on MMIC amplifiers, Phased Array Feeds, Integrated Receiver Development, and CDL's role in the future ngVLA and ALMA development will also be discussed.

302015-08-26 Wed
14:20~15:20
R1203
Anupreeta More
[Kavli IPMU]
Space Warps - crowd sourcing the discovery of gravitational lenses
Abstract

Strong gravitational lenses are useful for probing dark matter and cosmology. Gravitational lenses are rare and present significant challenges to find. Current algorithms are not efficient enough in finding lenses automatically. Better techniques are critical for discovering lenses from ongoing and planned large imaging surveys. Understanding the selection function of the lens samples is required for doing statistical studies. I will talk about Space Warps, a citizen science project to find strong gravitational lenses. I will discuss how the system works and how we determine the completeness and purity of our lens samples. The first lens search in Space Warps was done with the CFHT Legacy Survey (CFHTLS) data. I will present the results from this search.

312015-08-19 Wed
14:20~15:20
R1203
Thomas Greve
[University College London]
[CII] is all the rage at high-z - but how to make sense of it?
Abstract

In this talk I will present new SIGAME simulations of the [CII] 157.7um fine structure line emission from cosmological smoothed particle hydrodynamics (SPH) simulations of main sequence galaxies at z = 2. The gas in our galaxy simulations is modelled as a multi-phased interstellar medium (ISM) comprised of molecular gas residing in the inner regions of giant molecular clouds, an atomic gas phase associated with photodissociation regions at the surface of the clouds, and a diffuse, fully ionized gas phase. Taking into account heating by the local FUV radiation field and cosmic rays - both scaled by the local star formation rate density - we calculate the [CII] emission from each of the aforementioned ISM phases. The [CII] emission peaks in the central (<~ 1 kpc) regions of our galaxies where the star formation is most intense, and we find that the majority (>~ 60%) of the emission in this region originates in the molecular gas phase. At larger galactocentric distances (>~2 kpc), the atomic gas is the main contributor to the [CII] emission (>~ 80%), and at all radii the ionized gas provides a negligible amount (<~ 5%) to the [CII] budget. Our simulations predict a log-linear relationship between the integrated [CII] luminosity and star formation rate with a slope (0.80 +/- 0.12) in agreement with observationally determined slopes (~ 0.85 - 1.00) but with a ~ 3 times higher normalization than the observed z ~ 0 relation.

322015-08-18 Tue
14:20~15:20
R1203
Tony Mroczkowski
[United States Naval Research Laboratory]
*Special Seminar*
Imaging of the Sunyaev-Zel'dovich Effect Using the Goddard-IRAM Superconducting 2-Millimeter Observer (GISMO)
Abstract

Clusters of galaxies are among the largest gravitationally-bound objects in the Universe, and are found at the intersections of the large filamentary structure known as the Cosmic Web, which connects them to other clusters and superclusters. Clusters therefore trace the large-scale spatial distribution of dark matter, and can be used in cosmological tests that are independent from, and complementary to, other probes such as the cosmic microwave background (CMB), supernovae, and baryon acoustic oscillations (BAO). One tool now being used to find clusters at high redshift is the Sunyaev-Zel'dovich effect (SZE), which has redshift-independent surface brightness. To accurately extract cosmological parameters SZE observations, one must better understand how the signature due to thermal pressure tracks the gravitational potential, or more generally: How well does the baryonic component trace dark matter? The Goddard-IRAM Superconducting 2-Millimeter Observer (GISMO) is a 2-mm (150 GHz) 128-element bolometer array that operated from the IRAM 30-meter Telescope, providing a resolution of 16.5''. In a handful of follow-up observations, it was able image the SZ decrement in high-redshift massive clusters. Newly-built, the 2nd generation, dual-band GISMO-2 instrument will double its 2-mm pixel count, providing 256 detectors with lower instrument noise than the original GISMO. Additionally, GISMO-2 will simultaneously image the SZ increment and mm-wave sources with 1280 detectors operating at 1.2 mm (250 GHz). I will present GISMO SZ imaging of a few massive high-redshift clusters, and discuss prospects for GISMO-2 in combined studies using the 2nd generation MUltiplexed SQUID/TES Array at Ninety GHz (MUSTANG-2) from the 100-meter Green Bank Telescope.

332015-08-05 Wed
14:20~15:20
R1203
Aaron Evans
[University of Virginia / NRAO]
The Great Observatories All-sky LIRG Survey: A VLA and Herschel View
Abstract

Luminous Infrared Galaxies (LIRGs) are observed primarily to be interacting and merging galaxies. They are the sites of rampant star formation and active galactic nuclei (AGN) which are fed by abundant supplies of molecular gas. However, the very property that led to their initial discovery by IRAS as a significant galaxy population - their high infrared luminosity - also makes them difficult to study; the majority of the UV and optical light from young, massive stars and AGN is absorbed by obscuring dust and re-emitted in the infrared. The Great Observatories All-sky LIRGs Survey thus makes use of the diversity in wavelength coverage of the present space-based telescopes to probe the activity in a large (~ 100 - 200), flux-limited sample of LIRGs from the Revised Bright Galaxy Sample (RBGS). The first part of the talk will be devoted to discussing the survey as a whole. The latter part of the talk will be focussed on how our VLA and Herschel Space Observatory surveys are helping to shape the picture of star formation in extreme environments.

342015-07-30 Thu
14:20~15:20
R1203
Hsin-Yu Chen
[University of Chicago]
*Special Seminar*
Compact Binary Merger Rate, Detection, and Followup
Abstract

Compact binary coalescences (CBCs) are the most promising gravitational wave source for the LIGO/Virgo detectors. We predict the detectable rate of CBCs from short GRB observations, and constrain the GRB beaming angles from the non-detection of mergers in existing LIGO/Virgo data. The gravitational wave signals are almost impossible to obscure via dust absorption or other astrophysical processes, allowing us to derive the universal distribution of signal-to-noise ratios (SNR) for gravitational wave detection. This distribution guarantees the existence of high SNR events, and these provide the best constraints on source parameters such as sky locations. We discuss low-latency localization from these high SNR CBC detections, and some preliminary work on optimizing EM follow-up of CBC sources.

352015-07-29 Wed
14:20~15:20
R1203
Kinsuk Giri
[NTHU]
How does a Two Component Advective Flow Form?
Abstract

A black hole accretion is necessarily transonic. In presence of sufficiently high viscosity and cooling effects, a low angular momentum transonic flow can become a standard Keplerian disc except close to the hole where it must pass through the inner sonic point. However, if the viscosity is not high everywhere and cooling is not efficient everywhere, the flow cannot completely become a Keplerian disc. We show that, in agreement with the theoretical solutions of viscous transonic flows, matter having the viscosity parameter above a critical value becomes a Keplerian disc while matter having lesser viscosity remains a low angular momentum, sub-Keplerian flow. Thus, for instance, a flow having sufficiently high viscosity on the equatorial plane and low viscosity above and below would produce a two-component advective flow where a Keplerian disc is surrounded by a rapidly infalling sub-Keplerian halo. We find that the post-shock region of the relatively cooler Keplerian disc is evaporated and the overall configuration is quite stable. This agrees with the theoretical model with two components, which attempts to explain the spectral and timing properties of black hole candidates.

362015-07-23 Thu
16:00~17:00
R1203
Neal Evans
[University of Texas]
ALMA Observations of B335: Do Stars Form by Collapse?
Abstract

Observations of the isolated globule B335 with ALMA have yielded absorption features against the continuum that are redshifted from the systemic velocity in both HCN and HCO+ lines. These features provide unambiguous evidence for infall toward a central luminosity source. Models of inside-out collapse from an isothermal sphere can match the observed line profiles of HCN and HCO+ averaged over the central 50 AU.

372015-07-22 Wed
16:30~17:30
R1203
Roger Blandford
[KIPAC]
The Accelerating Universe
Abstract

From keV electrons in terrestrial aurorae to Ultra High Energy Cosmic Rays in unidentified "Zevatrons", the cosmos shows a plutocratic proclivity to concentrate energy in a tiny minority of suprathermal particles. The particle acceleration mechanisms involved can be traced back to the ideas of Faraday, Fermi and Alfvén though we are learning that the details are idiosyncratic and much can be learned from comparing and contrasting particle acceleration in laboratory and cosmic locations. Special attention will be given to acceleration accompanying strong shock fronts, spinning, magnetized compact objects and a new, general mechanism called “magnetoluminescence”.

382015-07-09 Thu
14:20~15:20
R1203
Yu Gao
[Purple Mountain Observatory]
The global star formation laws in galaxies
Abstract

The global star formation law — the relation between gas and star formation rate (SFR) — is studied in a large sample of 181 local galaxies with infrared (IR) luminosities (SFR) spanning almost five orders of magnitude. The surface density of dense molecular gas (as traced by HCN) has the tightest and linear correlation with that of SFR. We further show that the SFR and a variety of dense gas tracers (HCN, CS, their high-J, high-J CO) are all linearly correlated for both the Galactic dense cores in our Milky Way and star-forming galaxies near and far. This has immediate implications on the modes of star formation in galaxies and suggests that dense cores are the basic units in contributing to the star formation and the SFR might depend linearly upon the mass of dense molecular gas (the dense gas star formation law). These ground-based observations of last decade and recent Herschel results highlight what the ALMA can deliver on the studies of star formation laws at all redshifts and on all scales.

392015-07-01 Wed
14:20~15:20
R1203
Chia-Hsun Chuang
[Instituto de Fisica Teorica, UAM/CSIC]
Robust sub-percentage measurements from large-scale structure of galaxy clustering
Abstract

On-going and future galaxy surveys are going to reach sub-percentage accuracy on the cosmological measurements, e.g., Baryon Acoustic Oscillation, redshift-distortion, etc. A robust methodology is required while reaching such precision. Any minor systematic error from observations, data analysis, or theoretical models might be not negligible for future surveys. I would like to introduce the current methods, point out the potential systematics, and discuss the solutions.

402015-06-25 Thu
14:20~15:20
R1203
Kensei Kobayashi
[Yokohama National University]
Search for Relics of Chemical Evolution Toward Life’s Origin in Space
Abstract

Life’s origin was one of the biggest riddles remained for us. Since 1950s, a large number of laboratory experiments and theoretical consideration have been made to solve it. The standard scenario of the origins of life today is as follows: (1) Organic compounds such as amino acids were formed in primitive Earth environments or delivered from space, (2) further chemical evolution toward the first life system occurred in the primitive ocean. In addition, the possibility that life itself was delivered from space, now referred to as panspermia hypothesis, should also taken into account. However, the relics of the first life as well as organic compounds used for the first life were not remained in the present Earth. In these days, it becomes possible to find such relics in extraterrestrial environments. Primitive organic compounds in comets and asteroids can be directly studied through space missions. Titan, the largest moon of Saturn, may reserve some relics of chemical evolution in its atmosphere and liquidosphere. Mars and some other solar system bodies may cultivate life systems different from terrestrial one. In the colloquium, possibilities to find relics of chemical evolution in space will be introduce, as well as the results of laboratory experiments simulating chemical evolution in primitive environments.

412015-06-17 Wed
14:20~15:20
R1203
Wiphu Rujopakarn
[Kavli IPMU]
Resolving the Obscured Cosmic Accretion History and Modes of Galaxy Assembly
Abstract

Dust obscuration has hidden at least half of the cosmic accretion activity and concealed the most intense sites of star formation during the peak epoch for both processes in galaxy evolution at 1 < z < 3. Centimetric radio interferometry is the only means of identifying the AGNs and tracing star-forming activities at sub-arcsecond resolution, in an extinction-independent manner. I will discuss the use of radio survey to study star formation and AGN at 1 < z < 3, focusing on the early results from two ultra-deep 4-8 GHz Jansky VLA (JVLA) radio observations at 0.3" resolution in the UDS and HUDF fields. The goals of these surveys are to combine the radio data with the existing panchromatic observations to produce a complete census of AGN and to spatially resolve the star-forming galaxies. The ongoing survey in the HUDF, in particular, will reach 0.3 microJy/beam RMS and will provide the definitive radio dataset for spatially-resolved, ultra-deep, broadband extragalactic studies until the SKA era.

422015-06-10 Wed
14:20~15:20
R1203
Gary Fuller
[University of Manchester]
Peering into the Darkness: Infrared Dark Clouds & Massive Star Formation
Abstract

Most stars in our Galaxy form in clusters which often contain massive (M>8 Msol) stars which, with their prodigious energy output, eventually dominate the evolution of the interstellar medium. Understanding how these clusters and the massive stars within them form and evolve is one of the key questions for astrophysics. A major challenge is identifying the clumps of dense gas in molecular clouds which give rise to these clusters before the feedback from star formation significantly modifies their properties. Infrared dark clouds (IRDCs), dense regions seen in absorption against the diffuse infrared emission in the Galactic Plane, are amongst the best candidates for identifying such objects. In this talk I will draw on IRDCs identified in a recent new catalogue, plus other data including observations with ALMA, to explore how the gas in molecular clouds gathers to form massive dense clumps and how these subsequently evolve as star formation takes place within them.

432015-05-25 Mon
14:20~15:20
R1203
Timo Prusti
[ESA]
Gaia status and scientific performance
Abstract

The commissioning phase of the Gaia satellite was completed in July 2014 and we are well into the first year of routine phase operations out of the nominal 5 year mission. All subsystems are working and the operational parameters have been tuned for optimum science performance. A final upgrade of the on-board detection software is under testing. The aim is to be operational in the final configuration by summer 2015. The magnitude limit of the survey has been set to G=20.7 mag for astrometry and photometry. The spectroscopy magnitude limit is currently G_RVS=16.2 mag, but may be adjusted pending the new on-board software testing. The Science Alerts stream based on photometry has been started while preparations are underway for the first intermediate catalogue release by summer 2016. Examples of Gaia observations will be shown to indicate the scientific power of this ESA cornerstone mission.

442015-05-20 Wed
14:20~15:20
R1203
Joel Parker
[SwRI]
The New Horizons Mission - Pluto and Beyond
Abstract

The New Horizons spacecraft has spent the past nine years sprinting across the solar system to meet up with Pluto in July 2015. Even at this point, a few months out from the flyby, New Horizons is already returning images of Pluto as good or better than anything previously obtained. The spacecraft carries instruments covering ultraviolet, visible, infrared, and radio wavelengths to make surface and atmospheric observations of Pluto and its moons, and dust and particle instruments to study Pluto's environment and interaction with the solar wind. In this talk I will describe the mission and instrumentation, what we currently know about the Pluto system and the Kuiper belt, and what we hope to discover in the next few months at Pluto and the next few years as New Horizons passes through this "third region" of the solar system and possibly has another close encounter with a Kuiper belt object.

452015-05-13 Wed
14:20~15:20
R1203
Nicholas Altobelli
[ESA]
Rosetta - A Journey to our Origins
Abstract

Comets are the best sample of primitive solar nebula material presently available to us, dating back 4.57 billion years to the origin of our planetary system. Past missions to comets have all been “fast flybys”: They provided only a snapshot view of the dust and ice nucleus, the nebulous coma surrounding it, and how the solar wind interacts with both of these components. The Rosetta mission was set for a much more ambitious challenge - to accompany a comet nucleus on its journey around the Sun, monitoring the evolution of its activity, and deploy a lander on its surface. Rosetta is an ESA mission, with contributions from member states and from NASA, and it currently orbits the Jupiter family comet 67P/Churyumov-Gerasimenko (67P). After rendezvous on August 2014, the Rosetta spacecraft moved from 100 km above the nucleus to a bound orbit only ~10 km away. This early period of the mission has revealed previously unseen details of a comet nucleus, as Rosetta's instruments recorded measurements that were once impossible. After delivering the lander on November 2014, Rosetta began the systematic characterization of the nucleus and the monitoring of its activity, using a complex trajectory pattern offering complementary observation conditions. We review in this talk the knowledge acquired by the Rosetta mission so far.

462015-05-12 Tue
14:20~15:20
physics 104
Ron Taam
[ASIAA]
*ASIAA/NTU Joint Colloquium*
The Astrophysics of Stellar Mass Compact Objects
Abstract

Current developments in the astrophysics of stellar mass compact objects will be highlighted. Recent space based and ground based observations of X-ray point sources in our Galaxy and in external galaxies have led to a resurgence of interest in these objects. A brief overview of their observational properties will be introduced and our current physical understanding described. Many of these objects are transient, exhibiting time variations in both flux and spectra. By studying their behavior in both quiescence and in outburst, they can be used as cosmic laboratories to reveal the physics underlying their nature and state of evolution.

472015-05-05 Tue
14:20~15:20
Physics 104
Tim de Zeeuw
[ESO]
*ASIAA/NTU Joint Colloquium*
Building the world's largest optical telescope at ESO
Abstract

ESO is an intergovernmental organisation for astronomy founded in 1962 by five countries. It currently has 14 Member States in Europe with Brazil and Poland poised to join as soon as the respective Accession Agreements have been ratified. Together these countries represent approximately 30 percent of the world’s astronomers. ESO operates optical/infrared observatories on La Silla and Paranal in Chile, partners in the sub-millimetre radio observatories APEX and ALMA on Chajnantor and has started construction of the Extremely Large Telescope on Armazones near Paranal. La Silla hosts robotic and national telescopes as well as the NTT and the venerable 3.6m telescope. The former had a key role in the discovery of the accelerating expansion of the Universe and the latter hosts the ultra-stable spectrograph HARPS which is responsible for the discovery of many of the confirmed exoplanets with masses below that of Neptune. On Paranal the four 8.2m units of the Very Large Telescope, the Interferometer and the survey telescopes VISTA and VST together constitute a unique integrated system which supports 16 powerful facility instruments, including adaptive-optics-assisted imagers and integral-field spectrographs, with half a dozen more on the way and the 39m Extremely Large Telescope with its suite of instruments to be added in less than ten years. Scientific highlights include the characterisation of the supermassive black hole in the Galactic Centre, the first image of an exoplanet, studies of gamma-ray bursts enabled by the Rapid Response Mode and milliarcsec imaging of evolved stars and active galactic nuclei. The single dish APEX antenna, equipped with spectrometers and wide-field cameras, contributes strongly to the study of high-redshift galaxies and of star- and planet-formation. Early results obtained with ALMA demonstrate its transformational potential for high-resolution, high-sensitivity observations of the cold Universe, near and far. The colloquium will provide an overview of ESO’s current programme, with emphasis on recent increases in observing capabilities, consider ESO’s role in the broader context of astrophysics, and will briefly touch on opportunities for the future.

482015-04-29 Wed
14:20~15:20
R1203
Suklima Niyogi
[Leiden University]
Massive stars and cosmic interstellar dust
Abstract

Dust is a key component of the interstellar medium (ISM) of galaxies. Dust grains form primarily in the ejecta of the stars. The two main sources of dust are the winds of low-to intermediate mass (< 8 Msun) stars and the rapidly evolving high-mass stars (> 8 Msun). In our Milky Way Galaxy, low-mass stars mainly dominate the injection of dust into the ISM during the asymptotic giant branch (AGB) phase. But the origin of dust in galaxies in the very early universe is controversial. The observed high abundance of dust in galaxies in the early Universe has often been taken to imply that rapidly evolving, high- mass stars are an important dust source. To quantify the dust properties (e.g. mass, composition), I analyzed the spectral energy distribution (SED) of a sample of Luminous blue variables (LBVs) and B[e] supergiants in the Large Magellanic Cloud (LMC). For this purpose, I have used spectroscopic and photometric observational data from Spitzer Space Telescope and Herschel Observatory. I computed the model spectra of these stars by using radiative transfer code MCMax. From the best fit models, I derived the time-averaged dust mass-loss rates of these high-mass stars and compared with the dust mass-loss rates of low-mass AGB stars. Based on this analysis, I speculate that high-mass stars are an important dust source in the ISM of the LMC and further detailed investigation is required.

492015-04-22 Wed
14:20~15:20
R1203
Masashi Hazumi
[High Energy Accelerator Research Organization (KEK), Japan]
Roadmap for CMB Polarization Measurements with POLARBEAR, Simons Array and LiteBIRD
Abstract

Cosmological inflation, which is the leading hypothesis to resolve the problems in the Big Bang theory, predicts that primordial gravitational waves were created during the inflationary era. Measurements of polarization of the cosmic microwave background (CMB) are known as the best probe to detect the primordial gravitational waves. POLARBEAR is designed to measure CMB polarization with an array of TES bolometers. It has been in operation since 2012 in the Atacama desert in northern Chile. The main scientific objective of POLARBEAR is to search for primordial gravitational waves imprinted as the “B-mode” in the CMB polarization maps. Another important goal is to measure a spatial distortion of the CMB polarization maps due to gravitational lensing, which is a very sensitive probe for the large-scale distribution of matter in the early universe and will constrain the sum of neutrino masses. The Simons Array is an expansion of the POLARBEAR. It will consist of an array of three 3.5m telescopes each coupled to a multichroic TES bolometer pixel, so that it will provide very powerful foreground rejection capability and much deeper observation. Finally, LiteBIRD is a satellite project to map CMB polarization over the full sky at large angular scales with ultimate precision. The LiteBIRD proposal was submitted to JAXA in February 2015 with the target launch in Japanese fiscal year 2022. The scientific objective of LiteBIRD is to test all the representative inflation models that satisfy single-field slow-roll conditions and lie in the large-field regime. To this end, the requirement on the precision of the tensor-to-scalar ratio, r, at LiteBIRD is equal to or less than 0.001, a hundred times better than the current constraint.

502015-04-15 Wed
14:20~15:20
R1203
Vivian U
[UC Riverside]
Nuclear Gas Dynamics in Luminous Infrared Galaxies
Abstract

Gas-rich galaxy mergers provide a means to funnel gas into the central region of the system, consequently triggering episodes of nuclear star formation and supermassive black holes growth. The details of the fueling and feedback are often obscured by the cocooning dust stirred up from the violent interaction. To probe the small-scale gas kinematics in the inner kiloparsec region of these local luminous infrared galaxies requires high spatial resolution observations of their nuclei. Here I present results from our Keck Adaptive Optics near-infrared integral-field survey of the nuclear regions in 17 late-stage galaxy mergers. Our findings characterized and addressed the nature of nuclear disks, outflows driven by AGN and starbursts, as well as the role of mergers in black hole-galaxy bulge scaling relations. Our observations further enabled several case studies showing direct evidence of biconical molecular outflows as well as shocked gas from winds and ISM collision between progenitor galaxies.

512015-04-14 Tue
14:20~15:20
physics 104
Shude Mao
[NAOC]
*ASIAA/NTU Joint Colloquium*
Photometric and dynamical modelling of the Milky Way bar
Abstract

Milky Way is a typical barred spiral galaxy and is one of few galaxies where we can resolve the stellar populations. A thorough understanding of the Galaxy provides strong clues how other spiral galaxies form and evolve. However, our picture of the Milky Way is far from complete with many of its basic parameters remain ill determined. I will review some recent progress on the photometric and dynamical modelling of the Milky Way bar, and discuss future prospects in the field.

522015-04-13 Mon
14:20~15:20
R1203
Dan Jaffe
[University of Texas]
*Special Seminar*
IGRINS and the Revolution in High Resolution Infrared Spectroscopy of Young Stellar Objects
Abstract

The Immersion Grating Infrared Spectrograph (IGRINS) is the first of a new generation of infrared instruments with high sensitivity, high spectral resolution, and very broad spectral grasp. IGRINS, a joint project of the University of Texas and the Korea Astronomy and Space Science Institute, has been in regular operation on the McDonald Observatory 2.7m telescope since 2014 September. It has a resolving power of 40,000 and covers the entire 1.4-2.5 micron range in a single exposure. Even though it is only on a small telescope, IGRINS has less than a factor of 2 less sensitivity than CRIRES on the VLT while having 30 times the spectral grasp. A main goal for IGRINS is to characterize the evolution of young stellar objects and their protoplanetary disks over their entire early lives with quantitative measures of photospheric and disk properties. High resolution spectroscopy allows us to measure T_eff, log g, magnetic field, v sin i, veiling vs. wavelength, accretion rate, and other properties across a range of pre-main sequence stages with a common technique. We will present some of the early results from the instrument and describe the programs under way to meet our goal.

532015-04-08 Wed
14:20~15:20
R1203
Ian Dobbs-Dixon
[NYU Abu Dhabi]
Atmospheric Dynamics on Extrasolar Planets
Abstract

By far, the most thoroughly observationally and theoretically characterized extrasolar planets are the class of short-period, highly irradiated, gas-giant planets. Though much of our understanding of atmospheric dynamics and planetary evolution is derived from solar system planets, observations and models of these exoplanets have suggested the dynamics of their atmospheres is dramatically different than anything within our own solar system. Their short-periods suggest that these planets are tidally locked to their host stars, resulting in extremely large longitudinal temperature gradients. Coupled to the planets rotation, this results in semi-static, supersonic jets that dominate all other dynamical features above pressures of several thousand bars. I will discuss the multiple aspects of these models utilizing 3D radiative hydrodynamical models coupled to a variety of models exploring jet formation, the formation of exotic clouds, and overall planetary evolution. Detailed ‘observations’ of our models allow us to both benchmark our models and predict future observations.

542015-04-01 Wed
14:20~15:20
R1203
Chongsin Gou
[Advanced Rocket Research Center; National Chiao Tung University]
Rockets – the Key to Space, Can Taiwan Make It?
Abstract

In this talk, I will briefly review the current status of global space technology and application, which focuses on the use of satellites and satellite launching capability. Analyses show that Taiwan is highly justified to develop space technology in terms of her strength in economy and military spending by sending satellites into orbit to serve its people for peaceful/economic purpose. I will also propose what Taiwan should do in the near future to cultivate its own niche space technology which will benefit economic and scientific development. These include nano/micro satellites in LEO and skim satellite in VLEO, among others. Then followed by brief introduction of history, classification and pros/cons of rocket propulsion technology. This explains why ARRC is currently devoted to developing hybrid rocket propulsion technology. Its role in future space exploration is also outlined. In addition, I will share some recent studies done by a joint work between Prof. Nick Thomas (University of Bern, Switzerland) and my group about gas/dust jet plume simulation of CG/67P comet which were recently rendezvous by Rosetta satellite launched by ESA.

552015-03-31 Tue
14:20~15:20
Physics 104
Chao-Lin Kuo
[Stanford]
*ASIAA/NTU Joint Colloquium*
The search for gravitational waves in cosmic microwave background polarization: The recent BICEP2/Planck results and where do we go from here
Abstract

Polarization of the cosmic microwave background radiation is a powerful probe of the early universe. In particular, the so called B-mode polarization, a swirly spatial pattern in linear polarization, is a unique probe of primordial gravitational waves generated during inflation. After an overview of these concepts, I will give an update on the recent results from the BICEP/Keck experiments. These measurements made at the South Pole clearly detect a very significant B-mode signal at the relevant angular scales. Subsequent Planck high-frequency data, however, suggest that astronomical dust foregrounds could also produce a signal at this level. Regardless of existing uncertainties, I will argue that we are right at an important threshold of this exciting field. The recently deployed BICEP3 experiment will provide ground breaking sensitivity at a frequency that is much less affected by dust emission, using technologies and methodologies already vindicated by BICEP2 and Keck.

562015-03-25 Wed
14:20~15:20
R1203
Erick Young
[SOFIA Science Center]
SOFIA, The Stratospheric Observatory for Infrared Astronomy -- Science Highlights and Observing Opportunities
Abstract

The Stratospheric Observatory for Infrared Astronomy (SOFIA), is a highly modified Boeing 747-SP aircraft that has a 2.7-m telescope. Flying above more than 99% of the absorbing water vapor in the Earth's atmosphere, SOFIA provides access to otherwise unobservable wavelengths in the infrared to the worldwide astronomical community. SOFIA entered the Full Operations phase in February 2014, and is supporting observing proposals from astronomers all over the world. The project is an international collaboration between the US and Germany and has required high levels of coordination and communication among the many partners. The airplane has recently returned from an extensive periodic maintenance, and has resumed the science observation program. The plan for 2015 includes support for six science instruments, a deployment to the Southern Hemisphere, and support for an occultation of Pluto. This talk will cover some of the technical challenges in making SOFIA a reality, and will highlight some of the recent science results. Observing opportunities for Cycle 4 are described.

572015-03-18 Wed
14:20~15:20
R1203
Matteo Barnabè
[University of Copenhagen]
The dark and luminous structure of massive galaxies
Abstract

Understanding the formation and evolution of galaxies remains among the foremost open problems in present-day astrophysics and cosmology. A reliable and detailed description of the density profile, mass budget, structural properties and stellar initial mass function of galaxies through cosmic time is a much-needed step forward but – whereas nearby systems have been subject to intense scrutiny – painfully little is known about more distant ones, since observational limitations make it challenging to employ the traditional diagnostic tools. I will demonstrate how these difficulties can be overcome by combining the information obtained from all the available constraints: strong gravitational lensing, extended stellar kinematics and stellar population synthesis modeling. This approach makes it possible to conduct unprecedentedly detailed and robust investigations of the dark and luminous structure of massive ellipticals beyond the local Universe and, for the first time, to put strong constraints on both the steepness and the elusive lower mass cut-off of their stellar IMF. Finally, I will discuss how this joint technique can take full advantage of present and upcoming state-of-the-art instruments in order to advance our understanding of galaxy structure at higher redshifts and beyond the current mass frontier.

582015-03-17 Tue
15:20~16:20
physics 204
Chen Ning Yang
[Stony Brook University]
*ASIAA/NTU Joint Colloquium*
Conceptual Origin of Maxwell Equations and of Gauge Theory Phenotype
592015-03-12 Thu
14:20~15:20
R812
Chia-Chun Lu
[LeCosPA, NTU]
*Special Seminar*
An exceptionally powerful trio in the Large Magellanic Cloud
Abstract

The Large Magellanic Cloud, a satellite galaxy of the Milky Way, has been observed with the High Energy Stereoscopic System (H.E.S.S.) above an energy of 100 billion electron volts for a deep exposure of 210 hours. Three sources of different types were detected: the pulsar wind nebula of the most energetic pulsar known, N 157B; the radio-loud supernova remnant N 132D; and the largest nonthermal x-ray shell, the superbubble 30 Dor C. The unique object SN 1987A is, unexpectedly, not detected, which constrains the theoretical framework of particle acceleration in very young supernova remnants. These detections reveal the most energetic tip of a γ-ray source population in an external galaxy and provide via 30 Dor C the unambiguous detection of γ-ray emission from a superbubble.

602015-03-11 Wed
14:20~15:20
R1203
Shih-Ping Lai
[NTHU]
In Quest of the Youngest Protostars and Protoplanetary Disks
Abstract

Finding the youngest protostars and proto-planetary disks and investigating their environment is a critical step toward fully understanding of star formation. In this talk, I will present the work my students and I have done on this subject. (1) Discovering a extremely young Keplerian disk around Class 0 protostar VLA1623A with SMA and ALAM data (Murillo et al, 2013), (2) Introducing "Multi-D" - a new method we developed for identifying faint YSO population in Giant Molecular Clouds using multi-band photometry data (Hsieh & Lai 2013), and (3) Molecular line observations showing that Very Low Luminosity Objects (VeLLOs) are most likely young protostars (Hsieh et al, 2015, in print).

612015-03-04 Wed
14:20~15:20
R1203
Jun Hashimoto
[Oklahoma University]
Near-Infrared Imaging Observations of Transitional Disks in the Subaru/SEEDS project
Abstract

SEEDS is a strategic project in the Subaru telescope exploring exoplanets and circumstellar disks around 500 stars in the near-infrared wavelengths. The project has started in 2009 and will be completed in this year. Here, we review the project and summarize the major results especially in the survey of protoplanetary disks by near-infrared polarimetric imaging. In observing protoplanetary disks, we mainly focus on transitional disks known as a protoplanetary disk with a cavity in a central region of a disk. Disk-planet interaction would be one of intriguing interpretations potentially responsible for such a cavity-structure. Thus, transitional disks would be unique samples for understanding planet formation in a disk. As results of tens of observations in transitional disks, we have resolved fine structures in disks such as spirals, gaps, and dips at a radius of tens AU possibly due to gravitational interactions with unseen planet(s). These results may support planet formation at a wide orbit, e.g., GJ 504 b at 43 AU. We also found differences in structures of a cavity observed in the near-infrared and (sub-)millimeter wavelengths, i.e., a clear cavity in (sub-)millimeter wavelengths while no cavity in near-infrared wavelengths. The different behavior between small (sub-micron size) and large (millimeter size) dust grains would be consistent with disk-planet interaction plus dust filtration. Finally, we mention our preliminary results of disk demographics in transitional disks based on SEEDS data.

622015-03-02 Mon
14:20~15:20
R1203
Vincent Desjacques
[University of Geneva]
*Special Seminar*
Beyond CMB: large scale structure probes of inflation
Abstract

CMB measurements furnish to date the tightest constraints on the nature of the primordial fluctuations and, thereby, the physics of inflation. Interestingly, independent and competitive constraints can be obtained by measuring large scale density fluctuations in the low redshift Universe. I will describe recent theoretical and observational developments and show that, in the long run, large scale structure surveys may achieve limits on the primordial non-Gaussianity an order of magnitude better than Planck.

632015-02-25 Wed
14:20~15:20
R1203
Kevin Walsh
[Southwest Research Institute (SwRI)]
Planet Formation 2.0 - From Planetesimals to Planets
Abstract

Models of each stage of planet growth have mostly been successful at identifying the important physics in different regions of space at different times. The earliest stages are dominated by small-body physics, where sub-km-size bodies collide with each other and also interact with the gaseous solar nebula. Later, the gravitational interaction between planetary embryos on long timescales becomes more important. However, splitting the problem into different stages, each modeling subsets of the total physics, has an inherit weakness - planet growth does not progress at the same speed at all locations. Rather the inner regions of the Solar System may have many gravitationally interacting planetary embryos, while outer regions are still dominated by small-body collisions. Indeed, it has been recently shown that performing these simulations in a piecemeal way can lead us to fundamentally wrong conclusions about how the planets formed. Here we present simulations of planet formation from km-sized planetesimals all the way to planets. Using a particle-based code that models the fragmentation, accretion and dynamical evolution of a large number of planetesimals through the entire growth process we avoid the pitfalls of the classical piece-wise approaches. We generally find growth timescales that are far more dependent on distance from the Sun than previously expected. This leads to giant collisions between planetary embryos at 1 AU before Ceres-sized embryos have formed beyond 2 AU. We use these results to test classical models of Terrestrial Planet formation, including the recent Grand Tack model.

642015-02-24 Tue
15:20~16:20
R1203
Paulo Freire
[Max Planck Institute for Radio Astronomy]
*Special Seminar*
Testing general relativity and alternative theories of gravity with binary pulsars
Abstract

The last decade has witnessed a revolution in tests of general relativity using binary pulsars. First, the discovery of the "double pulsar", PSR J0737-3039, has greatly improved the quality (and quantity) of tests of general relativity possible with double neutron star systems. In particular, it has greatly improved the famous test of the emission of gravitational waves, which was originally carried out with the Hulse-Taylor binary pulsar, PSR B1913+16. In this talk I review some of the basics on pulsars and neutron stars, discuss the basics of pulsar timing and discuss in detail these classical tests and their results, with a particular emphasis on the upcoming results from the double pulsar. Second, the discovery of several tight binary millisecond pulsar systems with optically bright white dwarf companions like PSR J1738+0333 and PSR J0348+0432 has allowed extremely constraining tests of alternative theories of gravity from the combination of radio pulsar timing and optical spectroscopy of the white dwarf companion. In this talk I discuss this new technique and present some of the results, their constraints on alternative theories of gravity, and future prospects for improvements. If time allows, I will also mention some of the constraints on violations of the local Lorenz invariance of gravity. In the last part of the talk I discuss future and more powerful tests of GR with pulsars. The first one is a test of the strong equivalence principle (SEP) using the new millisecond pulsar in a triple star system, PSR J0337+1715. The second is a very precise test of the no-hair theorem for black holes with a hypothetical pulsar orbiting the super-massive black hole at the center of our Galaxy.

652015-02-13 Fri
14:20~15:20
R1203
Camilla Pacifici
[Yonsei University Observatory]
*Special Seminar*
What do the star formation histories of galaxies look like?
Abstract

The spectral energy distribution of the light emitted from galaxies across the electromagnetic spectrum contains a myriad of details about the stellar, nebular and dust components of galaxies. In the first part of the talk, I will present a new comprehensive library of galaxy spectra built by combining the semi-analytic post-treatment of a large cosmological simulation with state-of-the-art models of the stellar and nebular emission and attenuation by dust. A main novelty of our approach is the ability to interpret simultaneously the stellar and nebular emission from galaxies, even at low spectral resolution. In the second part of the talk, I will show how we can use this spectral library to constrain the physical parameters and star formation histories of low- and high-redshift galaxies. The results show us that simple declining functions of time are not always good approximations of the star formation histories of galaxies. Our approach can be used to extract valuable information from any kind of galaxy observation across the wavelength range covered by spectral evolution models as well as to plan for future galaxy observations.

662015-02-05 Thu
14:20~15:20
R1203
Fumitaka Nakamura
[NAOJ]
*Special Seminar*
Cluster Formation Triggered by Cloud-cloud collision: The Case of Serpens South
Abstract

Serpens South is an embedded cluster discovered by Spitzer. Its unique characteristic is the high fraction of Class 0/I objects, indicating that this cluster is just formed within 0.5Myr. Thus, Serpens South is an ideal object to study early phase of cluster formation. Based on our multiple molecular line data(N2H+, CCS, ...), we propose that cluster formation triggered by collisions of dense filaments whose dynamics is controlled by globally ordered magnetic field. We further propose a scenario that dense filaments are formed in the course of large-scale cloud-cloud collision. Cloud-cloud collision is probably one of the leading mechanism for triggering cluster formation.

672015-02-04 Wed
14:20~15:20
R1203
Sara Beck
[Tel Aviv University]
The Youngest Globular Clusters: Where They Are Born and How They Survive
Abstract

Where are globular clusters forming today? Not in our Galaxy; none of the protoclusters in the Milky Way is likely to survive as a bound cluster. The candidate proto-globulars in the nearby Universe are the optically hidden, deeply embedded super star clusters in starburst galaxies, where hundreds or thousands of OB stars form in volumes less than a few parsec across. Star formation eficiency (SFE) in these sources is 40 − 70%, more than an order of magnitude greater than in our Galaxy; why so high? OB stars create energetic feedback that will work to disperse the cluster: how do the clusters survive, and what do they do to the surrounding clouds? We report on SMA observations that may show how to drive high SFE, and infrared spectra of metal lines with true resolution of 3 − 5 km/sec that trace the kinematics of the ionized gas and its interaction with the ambient molecular material.

682015-01-28 Wed
14:20~15:20
R1203
Ivy Wong
[Univ. of Western Australia]
How Do Galaxies Stop Forming Stars?
Abstract

The Local Universe provides an excellent laboratory for studying the detailed processes of star formation and galaxy evolution. In this seminar, I will present some recent highlights from my work on blue early-type galaxies. Our latest model demonstrate that the observed "Green Valley" can be reproduced by two star formation truncation pathways for the evolution of galaxies. We previously found that the local post-starburst galaxies occupy a well-defined region in the low-mass end of the "Green Valley" and that even though star formation has only recently turned off, their morphology already resemble those of the low-mass red sequence galaxies. Since the post-starburst population is far too evolved, we probed the atomic gas content of its predecesssor population, namely, the blue early-type galaxies to search for the smoking gun that caused the sudden truncation of star formation. Our pilot study suggest that a kinetic process (probably AGN feedback) is driving the quick truncation of star formation in these systems, rather than a simple exhaustion of gas supply. In this talk I will also briefly describe some early results from the Radio Galaxy Zoo project.

692015-01-27 Tue
14:20~15:20
R1203
Ming-Tang Chen
[ASIAA]
*Special Seminar*
The Current Status of the Yuan T Lee Array
Abstract

The Yuan T. Lee Array for Microwave Background Anisotropy, or AMiBA, is a radio interferometry array for cosmology experiments. It consists of 13 co-planar, dual-polarization receivers operation at 3 mm wavelength. Its backend is a 4-lag, analog correlator covering a baseband bandwidth of 2-18 GHz, but with almost no spectral resolution capability. The 7-element AMiBA was dedicated in 2006, and subsequently upgraded to the full 13-element Array in 2010. The full array operations has continued for four years and finally ended by 2014. In this talk, I will report on the AMiBA’s current status, particularly on the development of the wide-band digital correlator. This development has enabled new capability for the Yuan T Lee Array, and is preparing the instrument for new research in cosmology science. I will show you the recent testing results of a 4-station digital correlator, and our plan for a new science endeavor to understand the physics during the Epoch of Re-ionization using the Yuan T. Lee Array.

702015-01-21 Wed
14:20~15:20
R1203
David Spergel
[Princeton University]
Searching for Gravitational Waves in the Microwave Background
Abstract

The detection of gravitational waves from the early universe would have a profound impact on our understanding of the early universe and would have an important implications for our understanding of fundamental physics. The BICEP2 team recently claimed to have made the first detection of gravitational waves. I will suggest that polarized dust is a more likely explanation and discuss the recent results from the Planck satellite. I will then look forward to upcoming experiments that will use multi-wavelength data to search for gravitational waves.

712015-01-14 Wed
14:20~15:20
R1203
Fred Walter
[Stony Brook University]
New Insights into Dust in the Environments of Novae from Chiron Spectroscopy
Abstract

When I started using SMARTS to observe galactic novae nearly 12 years ago, little did I know how challenging and engrossing this endeavor would prove. After all, the "nova problem" has been solved many times, and the novae have been thought to be almost fully understood. This could not be further from the truth. Novae, thermonuclear runaways on the surfaces of white dwarfs, explode and interact with their environments on timescales of days to years, which is ideal for synoptic monitoring with the SMARTS facilities at CTIO. After an introduction, I will discuss what high-cadence optical and near-IR photometry tells us about the formation of dust in novae. But photometry only tells part of the story. I shall focus on high-cadence high resolution optical spectroscopy of two disparate novae, the recurrent nova V745 Sco and the slow nova V1369 Cen. High spectral resolution reveals never-before seen details which likely will permit us to map the circumstellar environments of the long-period symbiotic systems like V745 Sco. V1369 Cen put on a show over Christmas 2013. Like other slow, dust-forming novae, it had multiple optical outbursts. Each of these corresponds to the appearance of a new spectroscopic absorption system. Nearly-daily observations for 5 months let us trace the dynamics of the envelope, and perhaps to view dust formation. In the past most novae have been ignored once they faded; long-term synoptic photometry and spectroscopy are showing that the novae are far more complex than we had assumed, but appropriate observations can and are revealing new truths about these "new stars".

722015-01-13 Tue
14:20~15:20
Physics 104
David Spergel
[Princeton University]
*ASIAA/NTU Joint Colloquium*
Planck and Beyond
Abstract

The Planck Telescope has made an accurate full-sky measurement of the cosmic microwave background (CMB) temperature, the leftover heat from the Big Bang. These measurements probe both the physics of the very early universe and the basic properties of the universe today. The Planck measurements confirm the earlier results from the WMAP telescope and rigorously test our standard cosmological model and provide an accurate determination of basic cosmological parameters (the shape of the universe, its age, and its composition). When combined with other astronomical measurements, the measurements constrain the properties of the dark energy and the nature of dark matter. The observations also directly probe the physics of first moments of the Big Bang: the current data are consistent with the idea that the early universe underwent a period of rapid expansion called inflation. Many key cosmological questions remain unanswered: What happened during the first moments of the big bang? What is the dark energy? What were the properties of the first stars? Dr. Spergel will discuss the role of ongoing and future CMB observations and describe how the combination of large-scale structure, supernova and CMB data can be used to address these key cosmological questions.

732015-01-08 Thu
14:20~15:20
R1203
Amy Lien
[NASA/GSFC]
*Special Seminar*
Ten years of Swift: The Third Swift Burst Alert Telescope Gamma-Ray Burst Catalog
Abstract

Gamma-ray bursts (GRBs) are one of the most energetic explosions in the universe, and can be observed across a wide range of wavelengths (from radio to GeV). Therefore, GRBs provide a rich environment to study astrophysics and a unique probe of cosmology, particularly the early universe. Swift, a multi-wavelength telescope dedicated to GRB study, marks its 10-year anniversary on Nov. 20, 2014. To date, Swift has discovered ~ 920 GRBs, within which ~ 315 GRBs have redshift measurements, ranging from z=0.03 to z=9.38. Here we focus on the Burst Alert Telescope (BAT) onboard Swift, the instrument that is responsible for triggering GRB detections. We present summaries of the BAT-detected GRBs for the past ten years, including temporal and spectral analyses of prompt emission and rest-frame properties. In addition, we perform searches for GRB emission beyond the event data (conventional data range for GRB analyses) using the BAT survey data, and report a list of GRBs with confirmed extended emission.

742015-01-07 Wed
14:20~15:20
R1203
Chien-Hsiu Lee
[Munich University Observatory]
PAndromeda - a dedicated M31 survey with Pan-STARRS 1
Abstract

The 3-year, high-cadence PS1 Andromeda survey yields well-sampled light curves that improve our understanding of microlensing and variables in M31. As a preliminary study, we discover 6 microlensing events in the inner bulge of M31. This demonstrates that deep data with good temporal resolution are essential to reveal microlensing events. We also explore the data for variability studies, and produce catalogs of ~300 eclipsing binaries, ~2000 Cepheids and other variables. We select bright eclipsing binaries for spectroscopic follow-up, to obtain a direct distance estimate of M31. We astromatrically align the multi-band Panchromatic Hubble Andromeda Treasury (PHAT) data to our PS1 images, and derive precise period-luminosity relation (PLR) for the Cepheids. The accurate distance and precise PLR will render M31 a distance anchor and help to reduce the error budget of Hubble constant. To fully exploit the value of PAndromeda, we welcome external collaborators, and can provide PS1 light curves with linked HST photometry upon request.

752015-01-06 Tue
14:20~15:20
R1203
Chieh-An Lin
[CEA Saclay]
*Special Seminar*
A New Model to Predict Weak Lensing Peak Counts
Abstract

Weak lensing has been shown to be a powerful tool for cosmology. In this talk, I will present a new model to study weak-lensing peaks, which contain rich non-Gaussian information. Based on a probabilistic approach, our model performs "fast simulations" to predict peak counts. This is based on two hypotheses: first, unbound and diffuse matter contributes little to peak abundance, and second, halo spatial correlation has a minor influence. The prediction carried out by our model is in a good agreement with N-body simulations, whereas the computation time has time largely reduced. I will highlight that our model can discriminate between various combinations of cosmological parameters, and that its high flexibility makes the use of peak counts under realistic survey conditions feasible.

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