Over the last few years, first systematic blind searches in the halo of the Milky Way based on the Sloan Digital Sky Survey data have uncovered a surprisingly large number of ultra-faint dwarf galaxies, members of a previously unseen class of stellar systems with extremely low star densities and less stellar content than a typical globular cluster. It is believed that these optically highly elusive aggregates of shining baryons hold the greatest leverage for testing dark matter theory and galaxy formation models. I will give an overview about the most recent findings in this research field and discuss the role of the new Stromlo Milky Way Satellites (SMS) Survey in providing the empirical input crucial to better understand and possibly reconcile the severe discrepancies that currently exist between observations and Cold Dark Matter model predictions on galaxy scales.

I report on an ongoing project that intends to bring together the galaxy content of observed and modeled galaxy clusters of the present-day universe. The known nearby, massive galaxy clusters serve as our observational reference. The model galaxies are provided by a recent semi-analytic model that combines galaxy formation physics with simulated hierarchical structure formation in a standard Lambda-CDM universe. We are particularly interested in the question whether the properties of the observed large and diverse dwarf galaxy population are reproduced in the model, something that could hardly be investigated with earlier models. Should the model fail to reproduce them, would it mean that many dwarf galaxies are created by environmental mechanisms not included in the model? Or would it merely indicate that the complex physics of galaxy formation is not yet fully understood?

천문학자가 꿈인 청소년들이 많다. 그들의 꿈이 먼 곳에 대한 동경을 핵으로 하고 있다 하여도, 천문학은 그만큼 매력적으로 보이는 분야라는 뜻일 것이다. 그리고 그들의 일부는 앞으로 천문학의 길로 들어서게 될 것이다. 그렇다면 천문학을(또는 넓게 과학을) 한다는 것은 어떤 뜻인가? 그것을 뛰어나게 하기 위해 어떤 준비가 필요한가?(특히 한국에서) 우리 청소년들은 그러한 준비를 하고 있는가? 만약 그렇지 않다면 어떻게 하여야 하는가? 이에 대한 답의 실마리는 현재 천문학자들만이 제공할 수 있다. 다음의 질문에 대한 천문학자들의 답이 현재 우리 청소년들이 서 있는 곳을 정확히 평가하고, 바라보아야 하는 방향을 제시하며, 바른 계획을 세우고 수행하여, 미래에 뛰어난 인재들이 천문학을 연구하며 행복한 삶을 영위하게 하는 초석이 될 것이다. “내가 교육을 받는 기간 동안 배웠으면 하고 지금 바라는 것들(하지만 배우지 못한 것들)은?”

Pre-main sequence clusters are excellent laboratories for studying dynamical interactions. Examples are the nearby eta Cha and epsilon Cha clusters,; sparse, compact, 5-10 Myr-old systems deficient by a factor of 2 in low-mass stars and brown dwarfs. Sensitive searches have completed the core population and found no members in the immediate field, to 2-3 times the core radius. The latest photometric and proper motion catalogues have sufficient precision to reliably detect members distant from the core. The observational constraints are severe; candidate members must be photometrical consistent with core members, have Li and other spectral indicators consistent with the cluster age, and have space velocities consistent with ejection early in the clusters life. In the case of eta Cha, candidates members have now been detected up to 5.5 deg spatial separation from the cluster core.

I present the mid-infrared (mid-IR) properties and environments of red-sequence galaxies within a supercluster in North Ecliptic Pole (NEP) area at redshift ~0.087, using AKARI NEP-Wide (5.8 deg2) IR imaging survey in conjunction with ultraviolet-near-IR spectral energy distributions. Most importantly, such mid-IR flux allows us to trace not only star formation rate (SFR), but also the presence of intermediate age populations showing excess emission over the stellar light in mid-IR. As such, we find that the red-sequence samples do not only contain passively evolving red early-type galaxies, but also contaminated with: 1) disk-dominated star-forming galaxies which have SFRs per unit stellar mass lower than blue-cloud galaxies, and 2) early-type galaxies showing broad non-stellar emission in mid-IR compared to normal red early-type galaxies. Those two populations may represent transition objects between blue spiral galaxies and red early-type galaxies. We present how those two transition galaxies depend on their local density and stellar mass, and discuss which factor is the primary predictor of star formation activity and the morphological transformation.

Newly formed massive stars can affect the parental molecular cloudsthrough ionization, heating, and expansion of the H II regions, stellarwinds, and supernova-driven shocks. For a better understanding of the feedback process in the interstellar medium, detailed observationsof the molecular clouds and identification of embedded young stellarobjects (YSOs) are required. In this talk, I will present results ofan extensive observational study of the active star-forming complex W51. First, I will show the spatial distribution and mass function ofembedded YSOs near the W51 giant molecular cloud over an area of 1.25deg × 1.00 deg selected from Spitzer Space Telescope data. Secondly, Iwill present the CO maps that was observed in the J = 2 - 1 transition of the 12CO and 13CO molecules with the University of Arizona HeinrichHertz Submillimeter Telescope and compare the molecular cloud morphologywith the distribution of infrared and radio continuum sources. Finally, I will explain the process of star formation triggered by the expansionof an H II region near W51A.

Participating in the "Dark Matter awareness week", a worldwide effort for disseminating specific information about Dark Matter, I will discuss the details of the mass discrepancy phenomenon in galaxies usually accounted by postulating the presence of a non luminous component. In the theoretical framework of Newtonian gravity and Dark matter halos, we start by recalling the properties of the latter as emerging from the state-of-the-art numerical simulations performed in the current LCDM scenario of cosmological structure formation. We then report the complex and much-telling phenomenology of the distribution of dark matter in spirals, ellipticals, and dwarf spheroidals. We will then highlight the impressive evidence that the distribution of dark and luminous matter are closely correlated, and finally point out some shortcomings of the model.

Gravitational Waves which arise from the fluctuating gravitational field have never been directly detected so far. I will briefly introduce what the gravitational wave is, the current status for the detection of gravitational waves and the prospect to use gravitational wave for the study of astronomical objects. Also some portion of this talk will be devoted to the research achievements in numerical relativity within the Korean Gravitational Wave Group.

Super smooth surfaces have been demanded on various optical materials in industry and science fields. Pitch polishing has been used for making glass optics for hundreds years in the world, though it is not suitable for modern optics in some cases. The new optics manufacturing technologies, such as, single point diamond turning, ultra-precision grinding and ultra-precision polishing will be described as well as manufacturing processes of X-ray mirrors.

Violent astronomical phenomena have been mostly explored by X-ray observations. Black hole is one of most exciting objects in the high energy Universe. Especially super massive black holes harbored in active galactic nuclei are deeply examined by ASCA and SUZAKU to provide us with direct evidence of strong gravitational field around black holes. In the latter half of the talk, developments of X-ray telescopes onboard previous and future missions will be described.

The cumulative distribution of stellar ages showed a distinct difference among star forming regions in NGC 2264. A Kolmogorov-Smirnov test gave a very low probability of them being from the same population. The results indicate that star formation in NGC 2264 started at the surface region (Halo and Field regions) about 6 -- 7 Myr ago, propagated into the molecular cloud and finally triggered the recent star formation in the Spokes cluster. The kind of sequential star formation that started in the low-density surface region (Halo and Field regions) implies that star formation in NGC 2264 was triggered by an external source.

KAIST Institute of Optical Science & Technology (KIOST)는 3년 전 KAIST 내의 융합연구의 실험을 위해 설립된 8개의 연구소 중의 하나이다. 설립의 취지는 최근에 많은 중요성이 부각되고 있는 펨토초 레이저를 중심으로 초고속 광학의 학제간의 연구와 실용화에 중점을 두고 있다. 참여하고 있는 학과로는 물리학과, 기계공학과, 화학과, 전자공학과, 그리고 생명공학과로 대표되며, 15명의 교수와 60 여명의 대학원생이 함께 일하고 있다. 본 연구소의 특징은 서로 다른 학문분야의 전문 가들이 초고속 광학에 공동 관심을 갖고, 새로운 융합연구의 주제의 발굴과 이의 구체화를 위해 노력하고 있다. 주요 연구분야는 펨토초 레이저 광원의 개발, 아토초 과학분야의 기본 연구, 시간 과 거리측정의 새로운 표준과 방법 개발, 생체와 의공학분야에의 응용 그리고 초정밀 레이저 가 공기술을 들 수 있다. 이번 강연에서는 학문적으로 매우 거리가 먼 연구집단들이 하나의 주요 공 통 관심사를 통해 함께 모여 파급효과가 큰 융합연구를 진행하고 있는 구체적인 사례를 발표하고 이에 대한 여러 의견을 교환하는데 주요 목적을 두고자 한다.

We present new measurements of the coherent motion of galaxies based on observations of the large-scale redshift--space distortions seen in the two--dimensional two--point correlation function of Luminous Red Galaxies in Data Release Seven of the Sloan Digital Sky Survey. We have developed a new methodology for estimating these coherent motions, which is less dependent on the details of galaxy bias and of the cosmological model to explain the late--time acceleration of the expansion of the Universe. We measure a one--dimensional velocity dispersion of galaxies on large--scales of sigma_v=3.01^{+0.45}_{-0.46} Mpc/h and sigma_v=3.69^{+0.47}_{-0.47} Mpc/h at a mean redshift of z=0.25 and 0.38 respectively. These values are fully consistent with predictions for a WMAP7--normalised LCDM Universe and inconsistent (at >5 sigma) with a Dvali-Gabadadze-Porrati (DGP) model for the Universe. We can convert the units of these sigma_v measurements to 270^{+40}_{-41} km/s and 320^{+41}_{-41} km/s respectively (assuming a LCDM universe), which are much lower than that expected based on recent low redshift (z<0.2) measurements of the peculiar velocity field (or ``bulk flows"), i.e., we would have predicted motions of ~ 600 km/s over our redshift range (0.16 < z <0.47) to be consistent with these local measurements. One possible explanation for such a large discrepancy is that our Galaxy is located in unusually over, or under, dense region of the Universe.

Our recent study of Galactic globular clusters using Ca and Stromgren uvby photometry has shown that many globular clusters have multiple red giant branch populations with distinct calcium abundances, in sharp contrast to the widely accepted idea of AGB pollution scenarios. This suggests that these globular clusters, like \omega Cen, are most likely the relics of more massive primeval dwarf galaxies that merged and disrupted to form the proto-Galaxy. In my talk, I will review current understanding of the multiple populations in globular clusters and will present some highlights of my survey.

The Lyman-alpha forest refers to numerous, narrow neutral hydrogen absorption lines blueward of the Lyman-alpha emission line ofhigh-redshift QSOs. The current paradigm of the Lyman-alpha forest favors that it arises from moderate amplitude density fluctuations in the warm (~10^4 K) photoionized, diffuse intergalactic medium(IGM) which traces the dark matter distribution in a simple manner. This interpretation has turned the Lyman-alpha forest into powerful cosmological probe at high redshifts, such as the matter power spectrum at smallest scales. They also provide a constraint onthe feedback between high-redshift galaxies and the IGM. At lower redshifts, the absorptions seen in low-redshift QSOs provide a clue on the missing baryon. In addition to this general discussion on the importance of the IGM, I will briefly discuss the current and upcoming instruments to study the IGM, such as COS on HST and the CODEX on the E-ELT.

One ingredient in an empirical birthrate estimate for pulsar binaries is the fraction of sky subtended by the pulsar beam: the pulsar beaming fraction. This fraction depends on both the pulsar’s beam geometry defined by the pulsar’s opening angle and the misalignment angle between its spin and magnetic axes. The current estimates for pulsar binary birthrates are based on an average value of beaming fractions for only two pulsars, i.e., PSRs B1913+16 and B1534+12. In this work, we revisit the observed pulsar binaries to examine the sensitivity of birthrate predictions to different assumptions regarding the pulsar beam geometry. The results show that, for those pulsars without any direct beam geometry constraints, the estimated beaming correction factor is likely to be smaller than six, a canonically adopted value when calculating birthrates of Galactic pulsar binaries. The median birthrate estimates for pulsar-white dwarf and pulsar-neutron star binaries in the Galactic disk, based on the best observational constraints, are 34 per Myr and 89 per Myr, respectively.

As the nearest rich and dynamically young galaxy cluster, Virgo is an ideal place to study great details of how galaxies interact with their surroundings. Using the data from our recent VLA HI imaging study (namely VIVA: VLA Imaging of Virgo galaxies in Atomic gas), I will present late type Virgo galaxies undergoing various environmental effects. I will discuss 1) which processes are dominantly affect galaxies in different density regions, 2) how far out the impact of the cluster reaches, and 3) how the environment may modify galaxies in morphology and color.

Shock waves in interstellar medium are collisionless and the shock transition is by the collective motion of underlying plasma (e.g., MHD turbulence). Two important consequences of collisionlesss shocks are 1) they do not partition energy equally among di?erent particle species, and 2) they accelerate cosmic rays. Balmer-dominated filaments, which represent fast non-radiative shocks into partially neutral medium, provide unique diagnostics for collisionless shocks. I'll review recent observations of Balmer-dominated filaments and their implication on the physics of collisionless shocks. In particular, I'll discuss how observations of Balmer-dominated filaments can constrain the cosmic ray acceleration process.

Plasma instabilities excited in collisionless shocks are responsible for particle acceleration. We have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electrons transverse deflection behind the shock. We calculate the radiation from deflected electrons in the turbulent magnetic fields. The properties of this radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants.

Nuclear rings are in most cases thought to be by-products of gas shock-focusing at Inner Lindblad Resonances (ILRs). AINUR (Atlas of Images of NUclear Rings) is an Atlas which includes images and metric measurements of all 113 known nuclear rings. This Atlas has been produced by checking and processing Hubble Space Telescope archive data from a complete sample of 488 galaxies. We made structure maps, Halpha and Paschen alpha continuum-subtracted images, and color-index maps in order to detect as many nuclear rings as possible. A few more nuclear rings have been added from a literature search. The 113 nuclear rings are found in 107 galaxies, six of which are elliptical galaxies, five are highly inclined disc galaxies, 17 are unbarred disc galaxies and 79 are barred disc galaxies. We find that dust nuclear rings are found in 6+-2% of elliptical galaxies and that star-forming nuclear rings occur in 19+-4% of the disc galaxies with types ranging from T=-3 to T=7. The peak of the star-forming nuclear ring distribution is found between Sab and Sb. The maximum possible radius for a nuclear ring in a barred galaxy is a quarter of the bar length. We find that the maximum possible relative size of a star-forming nuclear ring is inversely proportional to the non-axisymmetric torque parameter (``stronger bars host smaller rings'') and that the origin of nuclear rings, even the ones in non-barred hosts, is closely linked to the existence of dynamical resonances. We discuss implications for the lifetimes of nuclear rings and for the evolution of both the rings and their host galaxies.

To search for planets around intermediate-mass stars, evolved giant stars are the most suitable targets for Doppler spectroscopy-based planet searches because these stars have low surface activity and their spectra exhibit many sharp absorption lines. In recent years the number of planets found orbiting such evolved stars has dramatically increased and some properties of planetary systems have begun to emerge, although the number is still quite small compared with planets detected around solar-type dwarf stars. Now, we are carrying out a Korean-Japanese planet search program since 2005 and have just started a survey program of massive intermediate-mass giant stars in 2010. The aim of the programs is to show the statistical properties of planetary systems around intermediate-mass stars by precise radial velocity surveys of evolved GK-type giant stars together with collaborative surveys of the East-Asian Planet Search Network. In my talk, I introduce our planet searches and present current understandings of planets around evolved intermediate-mass stars.

Molecular outflows are believed to be an essential mechanism in the star formation process where they facilitate the collapse of a pre-stellar core into star by acting as a channel to remove an excess of angular momentum from the system. The outflows develop into massive extended structures hundreds of light years in length, and which evolve over timescales of tens of thousands of years. They may even be a source of turbulence in molecular clouds which helps regulate the star formation rate. We performed an investigation, via numerical simulations, of the properties of bipolar outflows and how they are effected by both the underlying jet beam and the surrounding ambient environment. Mass-velocity distributions were plotted in order to link the simulations to observations. Firstly we focused on simulating jets of various velocities and compositions, obtaining shallow mass-spectra (~1-2) which were independent of jet velocity, but found that steeper mass-spectra could be achieved through an atomic-jet/molecular-medium combination. Next we turned to the ambient environment and created realistic protostellar environments consisting of density gradients and density discontinuities. We found that a non-uniform medium lead to steeper mass-spectra, in line with those obtained from observations, and that the mass-spectrum of an outflow can vary substantially during its dynamical evolution.

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Studies of the highest redshift quasars probe the relation between the formation of the earliest supermassive black holes and galaxies. The quasar absorption lines trace the evolution of the intergalactic medium, and reveal when and how the reionization process happened, ending the cosmic dark ages. Detections of quasars at z>6 is challenging the standard picture of black hole growth in early Universe. They also show strong signs of on-going star-formation from their dust and gas emissions, suggesting the co-evolution of first generation black holes and galaxies. The absorption spectra of the highest-redshift quasars show strong evolution of Ly alpha optical depth, indicating that the neutral fraction of the intergalactic medium begins to increase rapidly, and suggests that we might be reaching the tail end of the reionization process.

Mass accretion onto compact objects like GBHS, NS and WD provides a platform to study the dynamics of material, structure and various physical processes. Here I show that the cross-correlation method is a potential tool to investigate and constrain the inner region of the accretion disk. The anti-correlated lags between two energy bands along with spectral studies can constrain the truncation accretion disk scenario in galactic black hole sources as well as in neutron star binary systems. We favour a geometry of accretion disk in which the soft photons are arriving from the Keprlerian disk and hard photons are originating from Compton cloud which is observed to be close to the central source. Such geometrical picture can consistently explain the lags, spectral changes along with rapid dynamical changes like QPOs. In case of Magnetic CV, anti-correlated lags can rigid the idea of blob accretion model which is often used to explain the excess soft X-ray spectral component in polars.

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Galaxy clusters are very important giant astrophysical laboratories in which one can study many interesting physical phenomena on giant scales. X-ray spectroscopy and analysis of the Sunyaev-Zeldovich effect play a crucial role to study interesting phenomena such as non-equilibrium ionization, non-thermal particle populations in galaxy clusters. The influence of high energy electron populations on measurements of metal abundances and on the He-like to H-like iron line ratio is considered. Measurements of the spectral slope of the Sunyaev-Zeldovich effect are proposed to obtain unbiased information about the specific properties of various electron distributions. It will be shown that the non-equilibrium ionization of iron can occur in galaxy clusters if the baryonic over-density is smaller than 11.0/tau, where tau<<1 is the ratio of the hydrodynamic structure age to the Hubble time.

예부터 우리 인간은 우주에 있어서 유일무이한 존재일까 하는 의문을 항상 갖고 있었다. 그 오랜 의문에 대한 대답이 前世紀가 끝날 무렵부터 서서히 밝혀지고 있다. 1995년, 스위스의 연구그룹이 페가사스座 51番星 주위를 돌고 있는 행성을 발견했다. 이 획기적인 발견에 의해 인간 이외의 지적 생명체의 존재를 찾는 여행의 一 幕이 열리게 되었다. 이러한 관측된 행성과 태양계의 행성과의 서로 다른 특징도 많이 볼 수 있다. 관측 기술의 진전에 따라 행성에 있어서 무엇이 보편적인 성질이고, 각각의 행성에 있어서 무엇이 특징인지 명확하게 되어가고 있는 것 같다. 그러나, 어떻게 행성이 형성되었는지의 이론적인 설명을 하지 않으면, 도대체 어떤 것에 의해 그 특징이 결정되었는지는 명확하게 할 수가 없다. 이론적인 행성형성의 설명이 이루어진다면, 형성된 행성표층의 환경까지도 推論 가능하게 된다. 推論된 행성의 표층환경에 대해, 생명에 대해 불가결한 아미노산이 형성 가능한가? 하는 생명의 기원에 관한 문제도 이론 가능하게 될 것이다. 이처럼 관측을 우선으로 한 행성형성의 이론적 짜임새를 만드는 것은 대단한 의미가 있다. 태양계 이외의 행성형성을 이론적인 검토를 하기 전에 자세한 관측이 가능한 태양계내의 행성형성과 원시지구 환경에 대해 조사, 연구하는 것은 대단히 중요하다고 생각된다. 본 강연은, 현재까지 얻어진 태양계형성에 관한 이론적 견해에 대해 소개하는 것을 목적으로 한다.

Massive stars and supernovae/GRBs are useful future tools for the probe of the early universe. As the formation of the first and second generations of stars is supposed to occur in metal-free/poor environements, the standard picture of massive stars, which is based on the sample in nearby galaxies including our own, may not be applicable. In this talk, I will address a few issues on the evolution of massive stars and their consequent explosions in the early universe. They include the effect of various physical processes (e.g. rotation, dark matter, pulsation) on the stellar evolution, the possibility of observing very energetic events like long gamma-ray bursts and some exotic types of supernovae at high redshift, and massive star populations in the early universe.

조선 후기에는 실학자를 중심으로 많은 서양의 학문을 받아들이는데 많은 노력을 기울였다. 그 중 역산 관련 전문 서적들 뿐만 아니라 천문도를 비롯한 다양한 천문기기들도 도입하여 사용하였다. 천문기기 중에서 역산과 관련하여 중요하게 사용되었던 것이 간평의다. 본 발표에서는 서양의 영향에 의해서 제작된 간평의의 역사와 구조 특징에 대하여 알아보기로 한다. 이것은 특정한 지방의 위도에 따라 일출 시각, 일몰 시각, 낮과 밤의 길이 등을 간단히 계산하고 쉽게 사용할 수 있다. 조선시대 정교하게 만든 간평의의 모습은 간단한 구조를 가졌지만 그 작도 방법은 쉽지 않다. 이러한 간평의를 정교하게 작도한 것으로 미루어 보아 당시 조선시대의 서양 천문학 지식의 이해 정도가 높았음을 알 수 있다. 이미 당시에 서양의 투영법이나 태양 운행과 관련한 작도를 능숙하게 할 수 있을 정도로 서양 천문학에 대한 이해가 높았다. 이러한 간평의의 제작은 당시 시헌력을 사용하면서 정기법을 이용한 태양의 일출 및 일입 시각을 절기와 관측 지방에 따라 정확하게 계산하는데 기본적 자료를 사용했다. 당시의 책력에 들어갈 가장 중요한 요소는 일출과 일몰 시각을 비롯하여 낮의 길이 변화에 대한 것이다. 이러한 간단한 기기를 이용하여 절기에 따른 각 지방의 일출과 일몰 시각 결정과 밤과 낮의 길이 결정을 손쉽게 할 수 있는 방법을 체득하고 있었다. 또한 이를 이용하여 역산의 편리성을 도모하였다.