• 천문학회지
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• 제37권5호
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• pp.605-609
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• 2004

We present a set of high-resolution 3D MHD simulations exploring the evolution of light, supersonic jets in cluster environments. We model sets of high- and low-Mach jets entering both uniform surroundings and King-type atmospheres and propagating distances more than 100 times the initial jet radius. Through complimentary analyses of synthetic observations and energy flow, we explore the detailed interactions between these jets and their environments. We find that jet cocoon morphology is strongly influenced by the structure of the ambient medium. Jets moving into uniform atmospheres have more pronounced backflow than their non-uniform counterparts, and this difference is clearly reflected by morphological differences in the synthetic observations. Additionally, synthetic observations illustrate differences in the appearances of terminal hotspots and the x-ray and radio correlations between the high- and low-Mach runs. Exploration of energy flow in these systems illustrates the general conversion of kinetic to thermal and magnetic energy in all of our simulations. Specifically, we examine conversion of energy type and the spatial transport of energy to the ambient medium. Determination of the evolution of the energy distribution in these objects will enhance our understanding of the role of AGN feedback in cluster environments.

• Mycobiology
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• 제48권1호
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• pp.20-28
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• 2020

Soil degradation can have an impact on the soil microbiota, but its specific effects on soil fungal communities are poorly understood. In this work, we studied the impact of soil degradation on the richness and diversity of communities of soil fungi, including three different degrees of degradation in Germany and Panama. Soil fungi were isolated monthly using the soil-sprinkling method for 8 months in Germany and 3 months in Panama, and characterized by morphological and molecular data. Soil physico-chemical properties were measured and correlated with the observed values of fungal diversity. We isolated a total of 71 fungal species, 47 from Germany, and 32 from Panama. Soil properties were not associated with fungal richness, diversity, or composition in soils, with the exception of soil compaction in Germany. The geographic location was a strong determinant of the soil fungal species composition although in both countries there was dominance by members of the orders Eurotiales and Hypocreales. In conclusion, the results of this work do not show any evident influence of soil degradation on communities of soil fungi in Germany or Panama.

• 천문학회보
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• 제37권1호
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• pp.40.2-40.2
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• 2012

Early-type dwarf galaxies are the most numerous galaxies in dense environments, making them ideal probes of the mechanisms that govern galaxy formation and evolution. Despite the common picture of an early-type dwarf galaxy as a quiescent one with no star formation and little gas, recent systematic investigations of early-type dwarf galaxies in the cluster revealed an unexpected variety among these apparently simple objects. In this talk, I review intriguing complexity of early-type dwarf galaxies in the cluster. I will also briefly introduce a new catalog of galaxies in the Virgo cluster using SDSS data, extended Virgo Cluster Catalog (EVCC).

• 한국경제지리학회지
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• 제26권3호
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• pp.202-222
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• 2023

본 연구는 서울의 영화산업과 방송산업 공간분포를 분석하고 집적지 변화에 작용하는 산업 성장과 도시 특성에 주목하여 서울 영상산업 클러스터의 공간적 특성을 파악하고자 한다. 1994년, 2004년, 2014년, 2021년의 서울시 사업체 조사를 분석자료로, 산업의 성장을 확인하고 공간적 자기상관성 분석(Moran's I와 LISA분석)을 수행해 영상산업의 공간분포와 집적지 변화를 확인했다. 또한 현직 종사자 인터뷰의 질적자료 수집과 분석으로 영상산업의 현황과 집적지 형성 요인 등을 파악하여 종합적인 분석을 시도했다. 분석 결과 영화산업과 방송산업 집적지는 서울에 분산되어 다핵형태로 성장하고 있다. 1994년에 영화산업 집적지는 충무로와 강남, 방송산업은 여의도로 집적지 구분이 뚜렷했던 반면, 2021년에는 마포와 강남이 영화산업과 방송산업의 공통 집적지로 나타났다. 그 외 여의도, 강서-영등포 일대의 방송산업 집적지와 성수 일대의 영화산업 집적지가 확인되었다. 끝으로 본 연구에서는 서울의 영상산업 성장과 공간적 분포 변화에 작용한 요인들을 영상산업의 특성과 도시환경의 변화와 연관시켜 제시하였다.

• 천문학회지
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• 제37권5호
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• pp.583-587
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• 2004

With the aim to investigate the statistical properties and the connection between thermal and non-thermal properties of the ICM in galaxy clusters, we have developed a statistical magneto-turbulent model which describes, at the same time, the evolution of the thermal and non-thermal emission from galaxy clusters. In particular, starting from the cosmological evolution of clusters, we follow cluster. mergers, calculate the spectrum of the magnetosonic waves generated in the ICM during these mergers, the evolution of relativistic electrons and the resulting synchrotron and Inverse Compton spectra. We show that the broad band (radio and hard x-ray) non-thermal spectral properties of galaxy clusters can be well accounted for by our model for viable values of the parameters (here we adopt a EdS cosmology).

• 천문학회지
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• 제38권2호
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• pp.207-210
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• 2005

We study the influence of rotation on the dynamical evolution of collisional single-mass stellar clusters up to core-collapse by using N-body simulations. Rotating King models which are characterized by dimensionless central potential parameter $W_o$ and the rotation parameter $W_o$ are used as initial models. Our results show that inner shells slowly contract until core-collapse phase is reached, followed by a slow expansion. Angular momentum is transported outward, while the core is rotating even faster than before, as predicted by gravogyro catastrophe theory. We confirm that rotation plays an important role in accelerating the dynamical evolution of stellar cluster, in particular in accelerating the core collapse.

• 천문학회보
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• 제40권2호
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• pp.40.2-40.2
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• 2015

In our recent investigation (Lim et al. 2015), we have shown that the combination of narrow-band Ca photometry and low-resolution spectroscopy can effectively search for globular clusters (GCs) with supernovae (SNe) enrichments. We apply this technique to the metal-poor bulge GC NGC 6273 and find two distinct subpopulations having different light and heavy element abundances. Our result suggests that NGC 6273 was massive enough to retain SNe ejecta, which would place this cluster in the growing group of GCs with Galactic building block characteristics, such as ${\omega}$ Centauri and M22.

• 천문학회보
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• 제40권2호
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• pp.33.2-33.2
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• 2015

The color distribution functions (CDFs) of globular clusters (GCs) in individual early-type galaxies show great diversity in their morphology. Based on the conventional "linear" relationship between colors and metallicities of GCs, the inferred GC metallicity distribution functions and thus their formation histories should be as diverse as they appear. In contrast, an alternative scenario rooted in the "nonlinear" nature of the color-to-metallicity transformation finds the various CDFs pointing systematically to a simple picture, i.e., such a high degree of variety stems predominately from only one parameter, the mean metallicity of GCs. The simulated CDFs of GCs aimed to reproduce 67 massive early-type galaxies from the ACS Virgo & Fornax Cluster Survey show that over 70% of the CDFs concur fully with the nonlinearity scenario. We discuss our new findings in terms of early-type galaxy formation in the cluster environment.

• 천문학회보
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• 제38권2호
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• pp.49.2-49.2
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• 2013

We report preliminary results from a radio study of central galaxies in cool and non-cool core clusters. A cooling flow is expected to rapidly form in the center of galaxy clusters unless additional heating mechanisms such as merging with sub clusters are at work. It has been suggested that cool flows can feed the AGN in the central galaxies, increasing their power. On the other hand, the AGN feedback can also affect the surrounding medium, heating back up the gas in the cluster core region. In this study, we investigate the co-evolution of cool flows and the AGN of galaxies located in the cluster center. For this study, we have selected 13 radio bright central galaxies from clusters with a range of cooling time scale. In this work, we present results of our recent observations using the Korean VLBI Network. We discuss the properties of the sample in radio and other wavelengths.

• 천문학회보
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• 제38권2호
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• pp.46.2-46.2
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• 2013

We utilize Sloan Digital Sky Survey DR7 spectroscopic data of ~380 star forming galaxies in the Virgo cluster to investigate their chemical properties depending on the environments. The chemical evolution of galaxies is linked to their star formation histories as well as to the gas interchange in different environments. We derived star formation rate (SFR) and gaseous metallicity (e.g., oxygen abundance) of star forming galaxies. Combining with GALEX ultraviolet photometry and ALFALFA HI 21 cm data, we examine the relations between SFRs, metallicity, and HI deficiency of galaxies in various regions of the Virgo cluster. We also quantify the degree of ram pressure around galaxy using the ROSAT X-ray surface brightness map. We discuss environmental effects on the chemical properties and evolution of star forming galaxies.