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Recent 3-7σ detections of parity asymmetry in the observed galaxy distribution have spurred interest in searching for potential signals of primordial parity violation. In this talk, I will explore the possibility of detecting parity-violation in primordial vector fossils using late-time galaxy spins. By leveraging N-body simulations, we employ halo spins as proxies for galaxy spins to examine the persistence of primordial vectorial parity asymmetry at low redshifts. Our method introduces a novel approach to generate initial conditions with significant parity asymmetry while keeping the initial matter power spectrum unchanged. By analyzing the helicity of the initial spin and halo spin vector fields, we detect substantial asymmetry in the initial spin field due to primordial vectorial parity violation, with over 50% of this asymmetry surviving in the late-time halo spin field across a range of scales. I will discuss the cosmological implications of our findings and conclude with prospects using galaxy surveys.

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We have undertaken a multidisciplinary study of the thermal decomposition of Murchison CM2 carbonaceous chondrite as an analog to metamorphic process that may have occurred on carbonaceous asteroids. The pre- and post-heated Murchison powders were analyzed using X-ray diffraction, thermal and evolved gas analysis, visible-near-infrared spectroscopy, microto nanoscale analyses included scanning and transmission electron microscopy. Mineralogical analyses of the unheated Murchison samples identified fine-grained serpentine, rounded Mg-rich serpentine (chrysotile-type), platy Fe-rich serpentine (cronstedtite-type), tochilinite, tochilinite-cronstedtite intergrowths, olivine, pyroxene, iron-nickel sulfides, magnetite, potassium iron-nickel sulfide, calcite, gypsum, apatite, Cr-bearing spinel, and chromite. The tochilinite shows the contorted morphology, mainly showing (002) lattice fringes of ~5.4 Å spacing and the identification of a new twinning relationship on the (032) plane. In response to thermal effects, serpentine group minerals are converted into mixtures of sub-μm olivine and pyroxene grains with similar Mg/Mg+Fe ratios as the precursor. Tochilinite breakdown forms troilite, magnetite, and minor Fe-Ni metal aggregates via amorphization. The thermal processing of Murchison carbonaceous chondrite produces distinctive micron and submicron structures that correspond to the breakdown of key minerals. These findings will be useful for understanding the thermal history of carbonaceous asteroids and for analyzing samples returned from ongoing missions to primitive asteroids (101955) Bennu and (162173) Ryugu.

During the last decades, the heliospheric studies significantly contributed to our understanding of how the Sun’s magnetic acitivity affects the space weather of Earth in the short term and its climate change in the intermediate term. It now seems quite timely or urgent to extend this expersise to resolve two outstanding problems: 1) how the solar magnetic activity have affected the habitability of Earth and other planets in the long term, and 2) how the magnetic acivity of a star affects the habitability of an exoplanet orbiting around the star. Resolving these two problems are intimately related to revealing of the fundamental principle and diversity of dynamo process in a variety of stars, planets and satellites. A useful tool for these scientific goals is comparative heliospheric studies: comparing Earth and Mars, comparing the present Sun-Earth system and the past system, comparing solar magnetic activity and stellar magnetic activity. Comparing flares between the Sun and other stars has become very active in the last decade, and comparing prominence eruptions between the Sun and stars is becoming popular, as prominnece eruptions are regarded as a signature of coronal mass jections that can be observed from the ground. In this talk, I will review the recent observations of flares and prominence eruptions on EK Dra that is regarded as a “young Sun”, in comparison with those on the Sun. We conclude that detecting prominence eruptions on a magnetically active star is much more difficult to detect flares, and would require high S/N spectroscopy as well as a reasonable model of radiation on the star during the eruptions.

I report on methods for the estimation of stellar parameters and elemental abundances, including [Fe/H], [C/Fe], and [Mg/Fe], for very large samples of stars in the disk and halo of the Milky Way, making use of a combination of narrow-band photometry from the J-PLUS and S-PLUS surveys and broad-band photometry from Gaia DR3. The techniques employed can achieve estimates with precisions that are commensurate with that obtained from low- and medium-resolution spectroscopy. I summarize the identification of on the order of 0.5 million carbon-enhanced metal-poor (CEMP) stars for future exploration of the chemo-dynamical properties of CEMP-no and CEMP-s stars in the halo and disk systems of the Galaxy.

The Dark Energy Spectroscopic Instrument (DESI) collaboration is conducting a five-year redshift survey of 40 million extra-galactic sources over 14,000 square degrees of the northern sky up to the redshift of 4 with the Mayall 4-meter telescope at Kitt Peak National Laboratory. One of its primary goals is to measure the cosmic expansion history precisely and accurately through the measurements of baryon acoustic oscillations (BAO). In this talk, I will present the analysis of the DESI First Year Baryon Acoustic Oscillations using the distributions of galaxies and quasars over the redshift range of 0.1-2, the estimates of the relevant systematics, and their intriguing cosmological implications, including the time-evolving dark energy.

Previously, offsets between galaxies and mass during cluster collisions were regarded as a promising indicator for evaluating the self-interaction cross-section of dark matter. However, past investigations based on these offsets have been hindered by significant biases regarding the phase and geometry of the merger. I will introduce a reliable constraint on the self-interaction of dark matter using a novel and effective approach with observations of cluster collisions featuring double radio relics. By utilizing the distance between relics relative to the distance between halos as a gauge for dark matter characteristics, we have established an upper limit of 0.33 cm^2 g^-1 for the self-interaction cross-section with 68% confidence. This marks the first robust outcome derived from colliding clusters, accounting for ambiguities such as mass variability, viewing angle, collision velocity, merger phase, impact parameter, and gas slope.

Photons looping around photon shells in black hole spacetimes form a sequence of higher order images -- the photon ring. Unlike in the case of the direct image, the size and shape of the photon ring reflects properties of spacetime, aka "clean geometry" with only limited impact of the configuration of the emitting source, aka "dirty astrophysics". Thus, they enable unprecedented robust observational tests of strong gravity, possibly including estimates of black hole spin, or constraining deviations from the Kerr metric. For at least 1 black hole in the Universe, M87*, the photon ring can be characterized with space radiointeferometry at mm wavelengths. I will talk about the ongoing plans and efforts to do it in the next decade with the

proposed NASA Black Hole EXplorer (BHEX) space VLBI mission.

Interferometer have already been commercialized and utilized in various fields, but it is too weeak to enviromental condition, its performance remains significantly limited. Therefore, research continues to apply advanced measurement techniques in various fields, such as optical measurement technology for gravitational wave detectors and large-aperture optical measurement technology. In this talk, I will introduce about birefringence sensor for test mass of gravitational wave detector and interferometric sensor for lareg-scale optics. In addition scattered light analysis from large scale optics will be introduced. 

본 세미나에서는 달 탐사를 위한 인공지능 기반 3차원 컴퓨터 비전 융합 기술을 소개합니다. 먼저, 연구실에서 수행해온 자율주행을 위한 3차원 시각인지 기법에 대한 대표 연구 성과를 살펴보고, 최신 인공지능 기법과 3차원 구조 복원 및 모델링 기술의 동향을 소개합니다. 이러한 기술들을 활용하여 달 궤도선 탑재체로 촬영한 영상을 통해 달의 3차원 지형을 복원하는 방법을 소개합니다. 특히, 기존 인공지능 및 컴퓨터 비전 분야의 태스크와 달 탐사를 위한 태스크의 차이점과 도전 과제를 분석하고, 이를 극복하기 위한 방안을 공유합니다. 이를 통해 인공지능과 컴퓨터 비전 기술이 달 탐사에 어떻게 혁신적인 변화를 가져올 수 있는지 논의하고자 합니다.