• 천문학회보
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• 제41권1호
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• pp.37.2-37.2
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• 2016

There exist scaling relations that link the mass of supermassive black holes with both the velocity dispersion and the mass of the central stellar cusp of their host galaxies. This implies that galaxies co-evolve with their central black holes, potentially through the feedback from actively accreting supermassive black holes (AGN). We use integral field spectroscopy data from the 8.2m Gemini-North telescope to investigate ionized gas outflows in luminous local (z<0.1) Type 2 AGN. Our sample of 6 galaxies was selected based on their [OIII] dust-corrected luminosity (>$10^{42}erg/s$) and signatures of outflows in the [OIII] line profile of their SDSS spectra. These are arguably the best candidates to explore AGN feedback in action since they are < 1% of a large local type 2 AGN SDSS sample selected based on their [OIII] kinematics. Expanding on previously reported results concerning the kinematic decomposition and size determination of these outflows, here we report their photoionization properties and energetics. We find strong evidence that connect the extreme kinematics of the ionized gas with AGN photoionization. The kinematic component related to the AGN-driven outflow is clearly separated from other kinematic components, such as gravitation- or stellar-driven motions, on the velocity and velocity dispersion diagram. Our spatially resolved kinematic analysis reveals that up to 90% of the mass and kinetic energy of the outflow is contained within the central kiloparcec of the galaxy. The total mass and kinetic energy of the outflow correlate well with the AGN bolometric luminosity, resulting in energy conversion efficiencies between 0.01% and 1%. Intriguingly, we detect ubiquitous signs of ongoing circumnuclear star formation. Their small size, the centrally contained mass and energy, and the universally detected circumnuclear star formation cast doubts on the potency of these AGN-driven outflows as agents of negative feedback.

• 천문학회보
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• 제44권1호
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• pp.36.3-36.3
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• 2019

Feedback process is one of the most important topics in the study of AGNs since it plays a key role in linking the SMBHs and their host galaxies. In order to further understand the co-evolution of SMBHs and their host galaxies, we probe the feedback process in local type-2 AGNs with a series of integral-field-spectroscopy observations. In the first part of my talk, I will introduce our GMOS observations of luminous type-2 AGNs at z < 0.1, which are selected using the integrated [O III] kinematics. Based on the dedicated emission-line diagnostics and kinematic studies, we identify the signatures of AGN-driven outflows and quantify the outflow size in the targets with extreme [O III] kinematics. For the targets without extreme [O III] kinematics, we find the presence of weak AGN-driven outflows, which are indicated by the significant differences between the kinematics of gas and stars. Then, I will present our recent study of 40 type-2 AGNs based on the SNIFS IFU. By comparing the radial profile of velocity dispersion of gas and stars, we measure the size of AGN-driven outflows in these targets and extend the outflow size-AGN luminosity relation in our previous GMOS studies. We also discuss the feedback effect of AGN-driven outflows by connecting the outflow velocity and host galaxy properties. These results highlight the importance of spatially-resolved observation in investigating gas kinematics and identifying the signatures of AGN-driven outflows.

• 해양환경안전학회지
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• 제28권2호
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• pp.394-405
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• 2022

본 논문은 CFD 해석법을 이용한 단일선체 및 이중선체 선박의 손상에 따른 기름 유출량 추정 결과를 소개한다. 수치해석 기법으로 다상유동 해석법을 사용하고 기름 유출 유동에 대한 다양한 수치해석적 조건의 변화에 대한 영향을 조사하였다. 좌초 또는 충돌에 의한 다양한 손상 조건에서의 기름 유출량의 변화를 해석하였으며 실험 결과를 통해 검증하였다. 본 논문의 수치해석 결과는 단일선체와 이중선체의 기하학적 특성을 따라 실험 결과와 잘 일치하였다. 특별히 물과 기름의 복잡한 상호작용이 나타나는 이중선체의 기름 유출 상황도 실험과 동일하게 타당하게 예측하였다. 본 연구를 통해 사고 선박의 기름 유출량 추정에 필요한 CFD기법을 정립할 수 있었다.

• 천문학회보
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• 제39권1호
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• pp.57.2-57.2
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• 2014

Protostellar jets and outflows are signatures of star formation and promising mechanisms for driving supersonic turbulence in molecular clouds. We quantify outflow-driven turbulence through three-dimensional numerical simulations using an isothermal version of the total variation diminishing code. We drive turbulence in real space using a simplified spherical outflow model, analyze the data through density probability distribution functions (PDFs), and investigate density and velocity power spectra. The real-space turbulence-driving method produces a negatively skewed density PDF possessing an enhanced tail on the low-density side. It deviates from the log-normal distributions typically obtained from Fourier-space turbulence driving at low densities, but can provide a good fit at high densities, particularly in terms of mass-weighted rather than volume-weighted density PDF. We find shallow density power-spectra of -1.2. It is attributed to spherical shocks of outflows themselves or shocks formed by the interaction of outflows. The total velocity power-spectrum is found to be -2.0, representative of the shock dominated Burger's turbulence model. Our density weighted velocity power spectrum is measured as -1.6, slightly less that the Kolmogorov scaling values found in previous works.

• 천문학회보
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• 제38권1호
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• pp.51.2-51.2
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• 2013

We present observational results of CO outflows towards 24 embedded young stellar objects (YSOs), which are selected from the targets of the Herschel key program, "Dust, Ice, and Gas in Time" (DIGIT). Molecular outflow activity, which is believed to have strong dependence on accretion process, is the most powerful in the early embedded phase of star formation and declines as the central protostars evolve to the main sequence stage. In order to study the relation between the CO outflows observed in low J transitions and the properties of protostars, we mapped the CO outflows of the selected targets in J=1-0 and J=2-1 with the 14-m TRAO telescope and the 6-m SRAO telescope, respectively. We also compare the CO outflow momentum fluxes with the FIR molecular line luminosities of CO, $H_2O$, OH, and OI, which were detected by the Herschel-PACS observations.

• 천문학회보
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• 제45권1호
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• pp.61.3-61.3
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• 2020

We present spatially resolved outflows and photoionization for a pilot sample of 11 type 1 AGNs (z<0.3) based on the Gemini Multi-Object Spectrograph Integral Field Unit data. These AGNs were selected since we found strong outflow signatures in SDSS spectra. We focus on [OIII] and Hα emission lines to probe outflow kinematics by measuring line flux, velocity, and velocity dispersion at each pixel. We investigate characteristics of gas kinematics of type 1 AGNs and compare them with those of type 2 AGNs in our previous studies. Furthermore, by drawing BPT map, photoionization states will be also discussed. Based on the results, we discuss various implications on the impacts of outflows on star formation in host galaxies.

• 천문학회보
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• 제40권2호
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• pp.41.4-42
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• 2015

Outflows and jets from young stellar objects (YSOs) are prominent observational phenomena in star formation process. Indicating currently ongoing star formation and directly tracing mass accretion, they provide clues about the accretion processes and accretion history of YSOs. While outflows of low-mass YSOs are commonly observed and well studied, such studies for high-mass YSOs have been so far rather limited owing to their large distances and high visual extinction. Recently, we have found a number of molecular hydrogen (H2 1-0 S(1) at 2.12 micron) outflows in the long, filamentary infrared dark cloud (IRDC) G53.2 located at 1.7 kpc from UWISH2, the unbiased, narrow-band imaging survey centered at 2.12 micron using WFCAM/UKIRT. In IRDC G53.2 which is an active star-forming region with ~300 YSOs, H2 outflows are ubiquitously distributed around YSOs along dark filaments. In this study, we present the most prominent H2 outflow among them identified in one of the IRDC cores MSXDC G53.11+00.05. The outflow shows a remarkable bipolar morphology and has complex structures with several flows and knots. The outflow size of ~1 pc and H2 luminosity about ~1.2 Lsol as well as spectral energy distributions of the Class I YSOs at the center suggest that the outflow is likely associated with a high-mass YSO. We report the physical properties of H2 outflow and characteristics of central YSOs that show variability between several years using the H2 and [Fe II] images obtained from UWISH2, UWIFE and Subaru/IRCS+AO188 observations. Based on the results, we discuss the possible origin of the outflow and accretion processes in terms of massive star formation occurring in IRDC core.

• 천문학회보
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• 제42권1호
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• pp.51.3-51.3
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• 2017

To investigate the connection between radio activity and AGN outflows, we present a study of ionized gas kinematics by using [O III] ${\lambda}5007$ emission line along the radio jet for six radio AGNs. These AGNs are selected based on the radioactivity (L1.4GHz ${\geq}$ 1039.8 erg s-1) as well as optical properties as type 2 AGNs. By using the high spatial resolution of the Red Channel Cross Dispersed Echellette Spectrograph at the Multiple Mirror Telescope, we investigate in detail the [O III] and stellar kinematics. We spatially resolve and probe the central AGN-photoionization sizes, which is important in understanding the structures and evolutions of galaxies. We find that the typical central AGN-photoionization sizes of our targets are in range of 1.8-3.8 kpc. We study the [O III] kinematics along the radio jets to test whether there is a link between gas outflows in the narrow-line region and radio jet emissions. Contrary to our expectation, we find no evidence that the gas outflows are directly connected to radio jet emission.

• Journal of Korea Trade
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• 제23권7호
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• pp.113-127
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• 2019

Purpose - This paper investigates whether financial crises could be the indicators of capital outflow waves or vice versa in Korea. Korea has experienced two severe financial crises, which are the Asian Crisis and the global financial crisis. Although there were many variables associated with these two remarkable events, one notable variable was gross capital outflows, which had significantly increased around them. Motivated by existing literature which built theoretical frameworks explaining the relationship between capital flight and financial crises, we examine the empirical evidence for this relationship. Design/methodology - We use panel data from 61 countries including Korea from 1980 to 2009 to study the associations between capital flight and diverse financial crises such as banking, currency, debt, and inflation crises. To be specific, we use the complementary log-log model to see whether capital outflow waves are reliable indicators for domestic financial crises. Findings - The results show, first, that banking, currency, and inflation crises are associated with capital flight. Second, debt crises are also associated with capital flight, but the result is not robust to different specifications. And, third, the positive associations between capital flight and crises are mainly driven by banking flows rather than FDI and portfolio flows. Originality/value - This paper is one of a few studies that investigates domestic (not foreign) investors' behavior during financial turmoil. Furthermore, theoretical studies which provide contradictory explanations on the movements of gross capital outflows during financial crises emphasizes the importance of empirical evidence in this paper.

• 한국산학기술학회논문지
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• 제18권6호
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• pp.312-318
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• 2017

본 연구는 비영리법인 의료기관이 영업활동에서 자금부족으로 인한 경영위험 상황에 대비하기 위하여 재무적 측면에서의 현금흐름 관리방안을 제시하고자, 비영리법인인 25개 종합병원과 23개 병원을 대상으로 재무정보를 이용하여 현금흐름을 산출한 후, 재무적 측면에서 영업활동에 필요한 자금인 순운전자본과 경영활동에 의한 자금의 동태적 개념인 현금흐름 간의 관계를 분석하였다. 분석결과, 결산연도별 산출지표 중 종합병원은 73.3%에서, 병원은 83.3%에서 영업활동에 필요한 자금인 순운전자본이 확보되지 않았었다. 순운전자본에 영향을 미치는 현금흐름 종류는 종합병원에서는 현금유출 없는 비용과 차입금 변동, 병원에서는 현금유출 없는 비용과 현금유입 없는 수익 그리고 차입금 변동이었다. 그러나 재무적 측면에서 영업활동에 필요한 자금이 확보되지 않았던 경우에, 종합병원은 현금유출 없는 비용인 감가상각비 등이 높고, 현금유입 없는 수익인 준비금 및 충당금 등이 낮아, 금융자금의 차입을 증가하게 되어 영업활동에 필요한 자금인 순운전자본이 낮아지게 되어 재무적 측면의 경영위험 환경이 되었다는 것을 알 수 있었으며, 병원은 현금유출 없는 비용이 높고, 금융자금의 차입을 증가시킴으로 인하여 영업활동에 필요한 자금인 순운전자본이 낮아지게 되어 재무적 측면의 경영위험 환경이 되었다는 것을 알 수 있었다. 따라서 경영활동에 있어서 실질적인 현금흐름의 안정성을 위해서는 현금의 유출이 없는 비용의 산정과 이들의 운용 등에 대한 적정성과 타당성 등을 검토해 볼 필요성이 있을 것이며, 현금흐름을 고려하여 체계적이고 합리적으로 자금관리를 하기 위한 적절한 내부정책방안의 검토가 필요할 것으로 사료된다.