A number of different scenarios have been proposed to explain the formation of massive stars. These include formation through the merger of less massive stars (coalescence model) or through the accretion of unbound gas from the molecular cloud (competitive accretion model). In the third scenario, the core accretion model, massive stars form through gravitational collapse, which involves disc-assisted accretion to overcome radiation pressure. This scenario is similar to the favored picture of low-mass star formation. Despite the likely importance of magnetic fields in the formation of low-mass stars, there are still only a few observations around massive stars, and theoretical simulations match the observations as long as the magnetic field is taken into consideration. Therefore, providing new measurements of magnetic fields orientation and strength at milliarcsecond resolution is fundamental to understand the formation process of high-mass stars. The best probes of magnetic fields in the high density regions close to massive protostars currently available are masers. In particular 6.7-GHz methanol and 22-GHz water masers. In the last six years we have studied the magnetic field around several massive young stellar objects by observing the polarized emission of water and, mainly, methanol masers. In my colloquium I will go through the results that we have achieved so far by emphasizing the most interesting cases.

Ghana has been enjoying space products for its socio-economic development for decades. Therefore, the idea of Ghana Space Science and Technology Center was conceived in 20008 but it was not until 2011 that the Centre was officially launched. The Centre has subsequently been upgraded into an Institute with three (3) research Centers, namely Radio Astronomy and Astrophysics, Remote Sensing and Climate Change, and Satellite Communication and Engineering. The Institute‘s mandate is to exploit the capabilities of Space Science and Technology for socio-economic development and to coordinate all Space related activities in Ghana. The Institute is engaged in joint projects and collaborations with partners globally. This presentation is to give an overview of activities at the Institute and also to showcase the opportunities for joint projects, capacity building and partnerships.

The Kepler space mission has discovered many planets around other stars, some of which are in the so-called habitable zone. In order for these planets to harbour terrestrial-type life, it is imperative that they experience a stable climate on long time scales. Earth experiences regular ice ages caused by perburbations from the other planets that cause the so-called Milankovic cycles. Such climate changes induced by the dynamics of the planetary system must be kept to a minimum. Here we report a case study of long-term climate cycles on the super-Earth HD 40307 g and extend this methodology to other systems.

Evolution of massive stars is determined by several important physical processes that we still do not fully understand theoretically. They include stellar wind mass loss, binary interactions, and stellar rotation. Interestingly, these three primary factors for the evolution of massive stars are closely related to production of hydrogen-deficient massive stars. The best known example is Wolf-Rayet stars: it is believed that the hydrogen-rich envelopes of their progenitors have been stripped off via stellar winds. Binary interactions and rotationally-induced chemical mixing can also make important contribution to the production of hydrogen-deficient stars. Wolf-Rayed stars and other forms of hydrogen-deficient stars (e.g., helium stars in massive binary systems) may produce a number of ionizing photons, and eventually explode as core-collapse supernovae of Type IIb, Ib and Ic or as long gamma-ray bursts depending on their final structure at the pre-collapse stage. Observing these stars and their explosions would therefore provide excellent constraints for stellar evolution theory. In this talk, I will review evolutionary scenarios of massive stars towards hydrogen-deficient stars, and their confrontation with recent observations.

Since 1964, NASA has sent flybys, orbiters, landers, and rovers to Mars, and is ready for a sample return mission in 2020’s and human exploration in 2030’s. In my talk, we will look into the cultural and historical background of Mars exploration, and overview past, present, and future NASA missions while updating Curiosity’s findings as of May 2015. We will examine NASA Mars missions’ impact on science, and technology, STEM education, and economy. Furthermore, we will go over NASA’s readiness for human exploration and the significance of Mars missions to our future generations. Lastly, I will update the international collaboration in NASA Mars missions. NASA는 지난 1964년부터 화성으로 비행선과 궤도선, 착륙선, 로버 등을 보냈으며 2020년대에는 시료 귀환임무를, 2030년대에는 유인탐사 임무를 준비하고 있습니다. 이 강의에서는 화성탐사의 문화적, 역사적 배경과 과거, 현재, 미래의 화성 탐사에 대해 소개하고 최근 발표된 큐리오시티의 탐사 결과를 알려 드리겠습니다. 또한 NASA의 화성 탐사 임무가 과학과 기술, 교육, 그리고 경제에 미치는 영향에 대해 말씀드리겠습니다. 아울러, NASA의 유인탐사 계획이 지금까지 얼마나 준비되었는지, 화성탐사가 미래 후손들에게 어떤 의미를 주는지 이야기 해보고 싶습니다. 마지막으로 화성탐사 임무에 관련된 NASA의 국제협력에 대해 말씀드리겠습니다.

Walter Baade, late in his career, was asked if he would choose a career in astrophysics if he had to do it all over again. He replied yes, but only if he could be assured that the ratio of total to selective dust extinction was universally 3. Many of us might add that we would want to be assured that the stellar initial mass function is also universal. Unfortunately, evidence is mounting that it is not. Of course, one person's misfortune is often another's gain - so perhaps variations in the IMF will help generate insights into a better understanding of star and galaxy formation. I will discuss an examination of this topic using Local Group dense star clusters.

무인기 군집 비행 기술 소개 - 임무 계획 기법을 중심으로

The deep gravitational potential wells of clusters of galaxies should capture fair samples of the total baryon fraction of the Universe, unless other physical processes drive baryons out of clusters. Thus precision measurements of the baryon fraction, particularly as a function of cluster mass, can reveal the history of baryon flux into and out of clusters. How those baryons are then apportioned between stars and intracluster gas---the star formation efficiency---informs models of cluster assembly and massive galaxy evolution, as well as efforts to use the cluster gas fraction to constrain the mass density and dark energy equation of state parameters. Even the partitioning of the stellar baryons alone, in and out of galaxies, tests models of cluster galaxy evolution, as intracluster stars are the final, unambiguous signature of stars stripped from cluster galaxies during tidal encounters. We have discovered that intracluster stars are a significant part of the stellar baryons in clusters and poorer groups of galaxies. I will present new work, including HST observations, characterizing the properties of this previously unexplored component, as well as the consequences for the cluster baryon budget and its relationship to the Universal value.

The objective-prism surveys such as HK and Hamburg ESO (HES) discovered numerous Very Metal-Poor (VMP; [Fe/H] < -2.0) stars in the Milky Way. Recently, the number of VMP stars has been dramatically increased to many tens of thousands, thanks to Sloan Digital Sky Survey (SDSS) and Sloan Extension for Galactic Understand and Exploration (SEGUE). Detailed chemical-abundance analyses, based on high-resolution spectroscopic follow-up, have revealed that, while most VMP stars exhibit similar abundance patterns, there are numerous examples of objects with peculiar chemical patterns. Among the chemically peculiar stars with [Fe/H] < -2.0, objects with enhanced carbon abundance are the most common variety. These are called Carbon-Enhanced Metal-Poor (CEMP) stars. One of the most interesting aspects of the CEMP stars is that the fraction of the CEMP stars increases as the metallicity decreases. In this talk, I will review the current understanding of the CEMP stars and discuss their implication to the first-generation stars and the origin of the Milky Way galaxy.

The ESA’s geomagnetic field mission, Swarm is composed of three satellites equipped identically with the Absolute Scalar Magnetometer (ASM), Vector Field Magnetometer (VFM), Langmuir Probe (LP), Thermal Ion Imager (TII), and Accelerometer. The three satellites were launched into the same altitudes (~500 km) with an orbit inclination angle of 87.3o. During the first two months the satellites were flying in a pearls-on-a-string configuration. Between February and April 2014 the spacecraft conducted orbit maneuver. Since 17 April 2014 the lower satellites, Swarm-Alpha and Swarm-Charlie have been flying side-by-side at altitudes around 470 km. The upper satellite, Swarm-Bravo flies higher by about 50 km, with the orbital plane being separated gradually from that of the lower satellite pair. Observation of ionospheric irregularities by the multiple Swarm satellites can help elucidate 3-dimensional morphology of the ionospheric irregularities. Selected examples of plasma density irregularities observed by Swarm are described in detail and discussed during this presentation.

Debris disks are the leftovers of planetary formation, revealing collisional debris from exo-Kuiper belt objects. Traditionally debris disks are found by deep searches of known nearby stars within 100 pc, which places obvious limits on the sample sizes that can be studied. Here I will outline a search technique utilising deep multiwavelength extragalactic surveys that opens up a radically new search space for debris disks and can reveal examples of disks that are too rare to exist in the local volume.

- Planetarium의 정의 - Planetarium의 탄생과 발전 - 우리나라 최초의 Planetairum과 역사 - 세계/우리나라 Planetairum 분포와 통계 - Planetarium의 역할과 미래

The Square Kilometre Array (SKA) project, which is the world-biggest international cm/m radio interferometer project, is now in the pre-construction stage 1 during which the SKA organization (SKAO) proposes options of elements and systems of the first 10 % construction of SKA called the SKA phase 1 (SKA1). SKAO has been re-baselining the SKA1 according to realistic costs and scientific updates since a release of the SKA1 system baseline design in March 2013. The re-baseline will be approved by the SKA board in early March. As for a science side, the science team in SKAO conducted an update of an international SKA science book. More than 120 chapters were proposed and accepted for publication last year. Finally, in Japan, NAOJ has started financial supports for Japanese SKA activities since last year. I am visiting in SKAO on secondment to play a role of a liaison, supported by NAOJ and SKAO. Japanese SKA science working groups have edited a Japanese SKA science book, in which they reviewed Japanese sciences with SKA. I will talk about these progress related to the SKA project.

In this talk, the multi-core fiber Bragg gratings (MCFBGs) is introduced and it is shown how they can be used in the astronomical purpose. Furthermore, the current status of the MCFBG development will be presented. Fiber Bragg gratings (FBGs) are the most compact and reliable method of suppressing atmospheric emission lines in the infrared for ground-based telescopes. Standard single core FBG based filters (GNOSIS) were demonstrated in AAT to eliminate 63 OH lines in 2011 and in . Inscribing FBGs on multi-core fibers offers advantages. Compared to arrays of individual single mode fibers (SMFs), the multi-core fiber Bragg grating (MCFBG) is greatly reduced in size, resistant to damage, simple to fabricate, and easy to taper into a photonics lantern. AAT and the University of Sydney are developing the next generation of GNOSIS (PRAXIS). In addition, I would like to briefly introduce various instruments for the astronomical purpose in Astrophotonics group of AAO and the University of Sydney including an optical angular momentum (AOM) measurement as well as a microspectrograph (NanoSpec), which is the world’s first photonics-based spectrograph and have been developed to be shipped in a micro-satellite (i-Inspire). The i-Inspire has been tested in a weather balloon in 27 km altitude in 2012 and will be launched. The arrayed-waveguide-grating (AWG) based filter development will also concisely be presented.

This talk is a review of the current status of the luminosity function for broad-lined unobscured AGN, along with implications for triggering and black hole growth, and a look at the unresolved issues. It is inspired by the 50th anniversary in 2013 of Schmidt’s discovery of the nature of the quasar redshift to reflect on the state of knowledge and context of early determinations of the quasar luminosity function vs. those today. The rapid evolution of the high-z luminosity function holds some promise for differentiating the physical processes responsible for triggering ? mergers, “cold flow”, or instabilities within the hosts. More data are still needed, particularly to characterize the faint end of AGN activity.

Recent developments in CMB and large-scale galaxy surveys have led to the standard cosmological model, but the physical understanding of its ingredients remains elusive so far. In response to the gravity of these issues, numerous large-scale galaxy surveys are ongoing or planned to be operational in a near future. However, precision measurements in future galaxy surveys bring in new challenges, demanding substantial advances in theoretical modeling and observational methods. I will discuss the recent theoretical development in modeling galaxy clustering in a relativistic context and the observational issues associated with this recent development. The relativistic effect in galaxy clustering or the deviation from the standard Newtonian description becomes substantial on large scales, in which dark energy models or alternative theories of modified gravity deviate from general relativity, and in which the fingerprint of the inflationary epoch remains in its pristine form. I will discuss how the subtle relativistic effect in galaxy clustering can be used to test general relativity on large scales and probe signatures of the early Universe.

The existence of the dark matter has been strongly supported from the cosmological observations such as the stellar rotation curves of spiral galaxies and the CMB measurements. The origin and nature of the dark matter however remain largely unknown, which has been among the most active research avenues in both particle physics and cosmology. This talk will give a theoretical overview on the current status of the dark matter studies, along with the examples for the attempts to search for them from the high energy physics and cosmology experiments.

Crowded regions of the sky present a significant challenge for stellar photometry. I will discuss how we use difference-imaging to extract the signals from variable stars from the background of constant-brightness objects, and show some examples from the KMTNet microlensing survey of the Galactic Bulge. I will briefly discuss the use of Graphical Processing Units (GPUs) for parallel computations in astrophysics, and describe pyDIA, a new GPU-based code for wide-field difference-imaging photometry.

Stars are opaque, so how can we work out their interior structure and the physical processes that are occurring inside them? Asteroseismology is the science of deducing stellar interiors from observations of a star’s surface oscillations. By monitoring a star’s tiny surface vibrations with a precision spectrograph, we can calculate that star's unique frequencies and modes of vibration, which are wholly governed by its interior structure. In this way, we can obtain tight constraints on the conditions within the star, which allows us to probe the relationship between the interior structure and the evolution of stars. In this talk, I will describe our observing programme at the University of Canterbury’s Mt John Observatory, where we obtain extensive high-resolution echelle spectra of non-radially pulsating stars. We analyze these to obtain the pulsational frequencies and identify these with the multiple pulsational modes excited in the star. I will present a summary of our observational program and some recent results from our spectroscopic frequency and mode-identification analysis.

Intensity interferometry, based on the Hanbury Brown--Twiss effect, is a simple and inexpensive method for optical interferometry at microarcsecond angular resolutions; its use in astronomy was abandoned in the 1970s because of low sensitivity. Motivated by recent technical developments, we argue that the sensitivity of large modern intensity interferometers can be improved by factors up to approximately 25,000, corresponding to 11 photometric magnitudes, compared to the pioneering Narrabri Stellar Interferometer. Our approach permits the construction of large (with baselines ranging from few kilometers to intercontinental distances) optical interferometers at the cost of (very) long-baseline radio interferometers. Realistic intensity interferometer designs are able to achieve limiting R-band magnitudes as good as m~14, sufficient for spatially resolved observations of main-sequence O-type stars in the Magellanic Clouds. Multi-channel intensity interferometers can address a wide variety of science cases: (i) linear radii, effective temperatures, and luminosities of stars; (ii) mass-radius relationships of compact stellar remnants; (iii) stellar rotation; (iv) stellar convection and the interaction of stellar photospheres and magnetic fields; (v) the structure and evolution of multiple stars; (vi) direct measurements of interstellar distances; (vii) the physics of gas accretion onto supermassive black holes; and (viii) calibration of amplitude interferometers by providing a sample of calibrator stars.

In this colloquium, I am going to mainly talk on my recent work on the tidal disruption of stars by supermassive black holes, specifically how accretion disks are formed around spinning supermassive black holes in tidal disruption events. Since I am moving from KASI to CBNU soon, I would also like to talk on how to find evidences for binary supermassive black holes on sub-parsec scales in the context of the binary-disk interaction, which is another topic I have been working on with colleagues in KASI.

Giant Lyman-alpha blobs with sizes of 50-100kpc represent dramatic episodes of on-going galaxy formation in the distant Universe. Research in the past decade has struggled to make progress on the question of what powers these huge Ly-alpha halos and whether the Ly-alpha-emitting gas is outflowing or infalling. In this talk, I will overview the recent progress in the Lya blob research, mainly based on my own works. First, I will present our deep and/or large area narrowband imaging surveys to identify tens of Lya blobs at redshifts ~2-5. These surveys have produced the first constraints on blobs' clustering and large-scale environment, showing that Lya blobs occupy massive halos likely to evolve into rich groups and clusters today. Second, we carried out large optical/NIR spectroscopic campaigns to investigate their gas kinematics. Our studies using non-resonant (optically-thin) emission lines show that there are only *weak* outflows within the blobs, therefore gas infall or extreme hyper/superwinds are not the source of the extended Ly-alpha emission. I will also present the first detection of molecular gas from a Ly-alpha blob and our on-going effort to characterize the physical conditions of its ISM. Lastly, I will discuss how the future facilities (GMT and ALMA) will play a role in revealing the nature of this mysterious sources.

천문학 분야 중 가장 빠르게 변화하는 분야가 있다면 그것은 태양계일 것입니다. 왜냐하면 우리는 이미 많은 탐사 장비를 태양계 곳곳으로 보냄으로써 과거에는 알 수 없었던 태양계의 많은 정보를 얻고 있는 시대에 살고 있기 때문입니다. 21세기 우주탐사시대를 맞아 태양계는 다다를 수 없는 곳이 아닌 개척의 영역으로 변하고 있습니다. 그리고 멀지 않은 미래에 우리나라도 태양계 탐사에 동참하게 될 예정입니다. 이번 강연은 인류가 살아가게 될 제2의 지구를 찾는다는 작은 주제를 가지고, 현재까지 인류가 찾아낸 태양계의 여러가지 모습들을 살펴보고자 합니다.

In the local universe, it is well known that various properties of galaxies show a clear environmental dependence. Still, it is an open question when and how this environmental dependence was developed and shaped. In this presentation, I will address this intriguing question, showing our recent results on the build-up of passive galaxies over a wide redshift range, from z~2 to z~0.5, focusing on its environmental dependence.

One of the main goals of physical cosmology is to find out the actual model of the Universe. Current standard model of cosmology, also known as concordance model, is a spatially flat FLRW Universe consist of weakly interacting cold dark matter, cosmological constant and baryons considering power-law form of the primordial perturbation. While we can use the data to model or reconstruct different characteristics of the Universe such as its expansion history or the form of the primordial spectrum, considering the data limitations and its uncertainties we have to deal with cosmographic degeneracies that makes it difficult to distinguish between different models. On the other hand one can use the power of the data to falsify different aspects of an assumed model using advanced statistical techniques. In my talk I review these two strategic approaches, 'reconstruction and falsification', highlighting the importance of each one and how they are connected; focusing on the concordance model of cosmology and how we can falsify this model.

Observations show that the Universe is fully ionized by z~6. The LyC photons from dwarf galaxies have been suggested as the most promising source of reionization, but little is yet known about how they escape from their host dark matter halos. In this talk, I will discuss two mechanisms (supernova feedback and runaway stars) that regulate the escape fraction at the epoch of reionization (z>7) by using high-resolution, cosmological radiation hydrodynamics simulations with adaptive mesh refinement. We find that a rapid build-up and subsequent destruction of star-forming clouds by SNe allows for the LyC photons to escape efficiently (~10%) through low-density channels. Inclusion of runaway OB stars further enhances the fraction (~14%), but the total number of escaping photons is found to be similar due to more effective suppression of star formation in this case. Both models (SN or SN+runaways) predict that a sufficient number of photons escapes from the halo at z~7 to keep the universe ionized, as observed. However, a still larger amount of ionizing photons appears necessary at z>9 to accommodate the electron optical depth inferred from the CMB measurements. I will finish the talk by discussing two possible solutions to this problem.

Coalescing compact binaries are the strongest gravitational wave emitters detectable by latest network of ground-based detectors that are ready to make detections beginning this year. However, in order to effectively localize the source of a gravitational wave signal as well as determine the parameters of the source and its environment, an electromagnetic counterpart is necessary. At present, there is convincing evidence that short gamma-ray bursts (sGRBs) are emitted by a compact binary merger, rendering it a promising electromagnetic counterpart for an impending gravitational signal. In this light, this work focuses on black hole-neutron star (BHNS) mergers as a viable site of sGRBs. More specifically, the work seeks to understand the role of the magnetic field of the neutron star companion in generating an sGRB. We use numerical relativity to study the magneto-rotational instability (MRI) as a viable magnetic field amplification mechanism in a BHNS merger and determine the possible outcomes that will render a BHNS merger as a promising sGRB site. We find that a large-scale poloidal field, which is necessary to collimate an sGRB jet, is likely generated via the MRI in the outer regions of the accretion disk of the black hole remnant.

Development of ASIAA and the Future of EAO

Chile is widely recognized as the leading site for ground-based observational astronomy in the world, with many first-class facilities and a growing local research community. In an effort to promote bilateral collaborations in astronomy, the Chinese Academy of Sciences (CAS) has recently established an office in Chile to coordinate its programs. I will introduce the operations of this office and its recent activities, then discuss its long-term mission and the prospect of international cooperation in the Southern Hemisphere.

I will present the star formation work we have done at Universidad de Chile. Starting with the establishment of the Maipu radio observatory in the 1960s, radio-astronomy was the first modern astrophysical expertise developed in Chile, before the advent of modern telescopes in the north of Chile. The 1980s brought the establishment of the 1.2m Columbia telescope at CTIO for the Milky Way CO 1-0 survey, and later the SEST 15m telescope. Thus, we began the study of dense gas in star forming regions. The 2000s brought the high frequency regime with the advent of the ASTE and APEX telescopes and now high angular resolution with ALMA. I will explain some of the survey work we have carried with the above instruments and how it led to the discovery of landmark sources that we are studying now with ALMA. Finally, I will mention what we hope to accomplish with ALMA in the forthcoming decade, in particular with the establishment of the Chilean Virtual Observatory.