• Communications for Statistical Applications and Methods
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• 제12권1호
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• pp.207-216
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• 2005

A binary segmentation procedure is a simple recursive approach to detect clusters and provide inferences for the study space when the shape of the clusters and the number of clusters are unknown. The procedure involves a sequence of nested hypothesis tests of a single cluster versus a pair of distinct clusters. The size and the shape of the clusters evolve as the procedure proceeds. The procedure allows for various growth clusters and for arbitrary baseline densities which govern the form of the hypothesis tests. A real tree data is used to highlight the procedure.

• Journal of the Korean Data and Information Science Society
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• 제28권6호
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• pp.1257-1260
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• 2017

최근 1인 가구가 급격히 증가하고 있으며, 그 증가의 원인 중 하나는 독거노인 수의 증가이다. 이러한 거주형태 변화는 필연적으로 정책적인 변화를 요구하므로 1인 가구의 공간적인 분포를 파악하는 것은 중요한 문제로 볼 수 있다. 또한 공간적인 군집이 나타나게 된 요인들에 대해 이해하는 것은 효율적인 정책 수립에 유리 할 것이다. 본 연구에서는 사회경제적인 불평등을 반영하는 박탈지수 (deprivation index)를 설명변수로 고려하면서 1인 가구와 저소득 독거노인에 대한 공간 군집 탐색을 하였다. 이를 위해서 fused lasso를 이용한 공간 군집 탐색방법이 사용되었다. 이 방법을 통하여 낮은 사회경제적 수준이 l인가구와 저소득 독거노인의 수에 얼마나 영향을 미치는지 확인하고, 박탈정도의 효과가 보정된 공간군집을 살펴보았다. 또한 정수형 자료에서 벌칙가능도함수를 이용한 공간 군집 탐색을 할 수 있도록 구현된 R패키지의 사용법을 자세히 소개하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.26-27
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• 2006

Characteristics of spatial structure of particle clusters are investigated by using the flow field data obtained from three-dimensional numerical simulations. Eulerian/Lagrangian approach with two-way coupling is applied and individual particle-particle collisions are taken into account by using the hard-sphere model. More than 16 million particles are traced in the maximum case. The results show that the cluster is consisted from the multiple-spatial scale components while the low wave-number, hence the large-scale structure, is dominant. Three-dimensional structure reconstructed from the low-pass filtered data enables us to investigate the essential dynamics of particle clusters in detail.

• 한국측량학회지
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• 제29권1호
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• pp.29-37
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• 2011

본 논문에서는 요인분석과 주성분분석을 이용해 수도권 지자체별 삶의 질 지수 측정하고 공간통계 및 지리적 탐색 기법을 이용하여 공간연관성 관점에서 수도권 삶의 질의 공간적 연관성을 분석하고자 하였다. 이를 위하여 2002년, 2005년, 2009년 수도권 삶의 질 지수 대상으로 전역적 Moran's I를 이용한 분석을 실시하였다. 또한 공간 연관성의 유형을 파악하고 실제 높은 삶의 질 지수를 나타내는 지역을 판별하기위해 모란산점도와 국지적 Moran's I 지수를 이용한 국지적 분석을 시행하였다. 삶의 질 지수의 분석 결과 서울시를 중심으로 높은 삶의 질 지수를 나타내었고 경기도 지역의 신도시를 중심으로 삶의 질 지수가 높은 양상을 보였다. 특히 서울강남3구(강남구, 서초구, 송파구)와 경기도 성남시에서 높은 삶의 질 지수를 나타내었는데, 이는 지방세 징수 상위지역으로 공공재 공급의 원천인 지역별 재정력의 차이가 삶의 질의 차이와 격차에 중요한 요인이 됨을 알 수 있다. 또한 수도권의 삶의 질 분포는 정적(+)공간연관성을 나타내며 국지적 규모의 분석결과, 서울시를 중심으로 H-H 클러스터가 경기도, 인천시를 중심으로 L-H 클러스터가, 그리고 경기도 외곽지역으로 L-L 클러스터가 형성되었고 그 패턴에 시간상의 큰 변화는 없었다. 하지만 대규모 인구유입이 있는 신도시를 중심으로 H-H 및 L-H 군집의 확산을 볼 수 있었다.

• 천문학회지
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• 제46권6호
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• pp.203-224
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• 2013

Wide-field $JHK_s$ images obtained with the SIRIUS near-infrared camera of the IRSF 1.4m telescope are used to examine the tidal structures of the spatial stellar configuration around six metal-poor ([Fe/H]< -1.0) globular clusters located within 3 kpc from the Galactic center. The radial surface density profiles are obtained from the surface photometry of the cluster images and the star counting for the photometric data. For the star counting, candidates of cluster member stars are selected with an filtering algorithm in color-magnitude diagrams. We find that the six target clusters show tidal overdensity features in the radial surface density profiles. There is a break inside the tidal radius for each cluster, and the profile in the outer overdensity region is characterized by a power law. Two-dimensional density maps of all the clusters show distorted asymmetric stellar configurations in the outer region. In five out of the six target clusters, the overdensity features are likely to be associated with the effects of the Galaxy dynamical interaction and the cluster space motions. The observed tidal configurations of stars suggest that several metal-poor clusters in the Galactic bulge are possibly surviving remnants of mergers to build the old stellar system of the Galactic bulge.

• 천문학회보
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• 제46권2호
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• pp.41.3-42
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• 2021

Coma cluster (Abell 1656) is one of the most massive local galaxy clusters such as Virgo, Fornax, and Perseus, which holds a large collection of globular clusters. Globular cluster systems (GCSs) in a galaxy cluster tell us a history of hierarchical cluster assembly and intracluster GCs (ICGCs) are known to trace the gravitational potential of the galaxy cluster. Previous studies of GCSs in Coma mainly utilized data obtained using Hubble Space Telescope (HST) with high spatial resolution. However, most of the data were based on narrow-field pointing observations. In this study we present the widest survey of GCSs in the Coma cluster using the archival Subaru/Hyper Suprime-Cam (HSC) g and r images, supplemented with the archival HST images. The Coma GCSs are largely extended in E-W and SW direction, along the general direction of Coma-Abell 1367 filament. This global structure of the GCSs is consistent with the spatial distribution of the intracluster light (ICL). ICGC spatial distribution is largely extended to almost ~50% of the virial radius. Most of these ICGCs are blue and metal-poor, which supports the scenario that ICGCs are mainly originated from dwarf galaxies and some proportion from brighter galaxies. Implications of the results will be discussed.

• 천문학회지
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• 제37권5호
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• pp.307-313
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• 2004

Clusters of galaxies are believed to constitute a population of astrophysical objects potentially able to emit electromagnetic radiation up to gamma-ray energies. Evidence of the existence of non-thermal radiation processes in galaxy clusters is indicated from observations of diffuse radio halos, hard X-ray and EUV excess emission. The presence of cosmic ray acceleration processes and its confinement on cosmological timescales nearly inevitably yields in predicting energetic gamma-ray emission, either directly deduceably from a cluster's multifreqency emission characteristics or indirectly during large-scale cosmological structure formation processes. This theoretical reasoning suggests several scenarios to actually detect galaxy clusters at gamma-ray wavelengths: Either resolved as individual sources of point-like or extended gamma-ray emission, by investigating spatial-statistical correlations with unidentified gamma-ray sources or, if unresolved, through their contribution to the extragalactic diffuse gamma-ray background. In the following I review the situation concerning the proposed relation between galaxy clusters and high-energy gamma-ray observations from an observational point-of-view.

• 천문학회보
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• 제45권1호
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• pp.62.2-62.2
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• 2020

Globular clusters(GCs) are found not only around galaxies (galaxy GCs), but also between galaxies in galaxy clusters (intracluster GCs; ICGCs). The ICGCs, which are not bound to any of cluster member galaxies, are governed by the galaxy clutster potential. ICGCs have been detected in the wide field of Virgo and Fornax galaxy clusters. However, previous surveys covered only a small fraction of Coma and Perseus. In this study we present a wide field survey of these two galaxy clusters, using Subaru Hyper Suprime-Cam(HSC) archival images, covering a circular field with diameter of ~1.8 deg. We select ICGC candidates, by masking the images of bright galaxies and choosing point sources in the remaining area. We find thousands of ICGCs in each galaxy cluster. These ICGCs show a bimodal color distribution, which is dominated by blue GCs. We investigate spatial distributions and radial number density profiles of the blue and red ICGCs in each galaxy cluster. Implications of the results will be discussed.

• 천문학회보
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• 제46권1호
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• pp.36.1-36.1
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• 2021

Galaxy clusters host Mpc-scale diffuse radio emission giving us evidence of large-scale magnetic fields in the Universe. It is relevant to understand magnetic field amplification processes occurring at the center and outskirts of galaxy clusters. Each of these processes are believed to give rise to observed radio haloes and radio relics, respectively. In this work, we focus on studying the continuum and polarised emission in radio relics. We use threedimensional magnetohydrodynamical simulations of merger shock waves propagating through a magnetized, turbulent intracluster medium. Our model includes the diffusive shock acceleration (DSA) of cosmic ray electrons, their spatial advection and energy losses at run-time. We discuss the relation between the mock observation features and the underlying morphology of the magnetic field.

• 천문학회지
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• 제38권3호
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• pp.345-355
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• 2005

We present a photometric study of the star cluster system in the merging galaxy NGC 1487, based on the BI photometry obtained from the F450W and F814W images in the HST /WFPC2 archive data. We have found about 560 star cluster candidates in NGC 1487, using the morphological parameters of the objects. We have investigated several photometric characteristics of the clusters: color-magnitude diagrams (CMDs), color distribution, spatial distribution, age, size and luminosity function. The CMD of the bright clusters with 18.5 < B < 24 mag in NGC 1487 shows three major populations of clusters: a blue cluster population with $(B-I){\le}0.45$, an intermediate-color cluster population with $0.45<(B-I){\le}1.55$, and a red cluster population with (B - I) > 1.55. The intermediate-color population is the most dominant among the three populations. The brightest clusters in the blue and intermediate- color populations are as bright as $B{\approx}18mag$ ($M_B{\approx}-12mag$), which are three magnitudes brighter than those in the red population. The blue and intermediate-color clusters are strongly concentrated on the bright condensations, while the red clusters are relatively more scattered over the galaxy. The CMD of these clusters is found to be remarkably similar to that of the clusters in the famous interacting system M51. From this we suggest that the intermediate-color clusters were, probably, formed during the merging process which occurred about 500 Myrs ago.