• Journal of The Korean Astronomical Society
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• v.19 no.1
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• pp.11-14
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• 1986

It is shown in this paper that the astigmatic property of single gravitational lens in static bounded gravitational field can be retained, if n-gravitating body as a whole acts simultaneously as gravitational lens.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.36.2-36.2
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• 2014

We present results of the analysis of FLS 1718+59, a galaxy-galaxy gravitational lens system in the Spitzer First Look Survey (FLS) Field. A background galaxy (z = 0.245) is severely distorted by an elliptical galaxy (z = 0.08), by gravitational lensing. We analyze this system by several methods, including Ellipse and Galfit fitting, gravitational lens modeling (gravlens), and SED fitting. Properties of the lens galaxy can be obtained: from Galfit we measure the effective radius and the average surface brightness inside it, and from gravlens we estimate the total mass inside the Einstein radius (lensing mass). We use these parameters to check that the lens galaxy is located on the Fundamental Plane. Also, we conduct SED fitting for the lens galaxy and estimate the stellar mass, and compare this with the lensing mass of the lens galaxy to check the M-L relation.

• Journal of The Korean Astronomical Society
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• v.29 no.1
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• pp.1-8
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• 1996

When we follow the lines of the trajectory of photons which intersect the circle, the circle may suffer some deformation as approaching to the observer. We consider an infinitesimal light bundle suffering gravitational bending. We examine the deformation of the deflected light bundle due to the gravitational lens. The size of the deformation is expressed in terms of the focal length of the gravitational lens.

• Journal of The Korean Astronomical Society
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• v.24 no.1
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• pp.1-12
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• 1991

The mathematical properties of gravitational lens equations are examined in the frame work of gravitational micro-lensing effects. The caustics of the gravitational lens may be defined in terms of "cusp" and "folding" in general. In some cases for overfocussing, however, the critical curves (caustics) have no cusp and no folding. If the observer is in the overfocussed region, he may not see any lensed image.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.52.1-52.1
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• 2013

We present new analyses of FLS 1718+59, a galaxy-galaxy gravitational lens system in the Spitzer First Look Survey (FLS) Field. A background galaxy (z = 0.245) is severely distorted by a nearby elliptical galaxy (z = 0.08), which can be interpreted as a result of gravitational lensing. We analyze this system by multiple methods, including ELLIPSE fitting, gravitational lens modeling, and surface brightness fitting. From this analysis, we obtain parameters of the lens galaxy using varying approaches and compare them. In the future, we will conduct SED fitting for the lens galaxy and estimate the stellar mass, and compare this with the total mass of the lens to check the M-L relation.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.401-403
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• 2015

We present the results of the analysis of FLS 1718+59, a galaxy-galaxy gravitational lens system in the Spitzer First Look Survey (FLS) field. A background galaxy ($z_s=0.245$) is severely distorted by a nearby elliptical galaxy ($z_l=0.08$), via gravitational lensing. The system is analysed by several methods, including surface brightness fitting, gravitational lens modeling, and spectral energy distribution fitting. From Galfit and Ellipse we measure basic parameters of the galaxy, such as the effective radius and the average surface brightness within it. gravlens yields the total mass inside the Einstein radius ($R_{Ein}$), and MAGPHYS gives us an estimate of the stellar mass inside $R_{Ein}$. By comparing these parameters, we confirm that the lens galaxy is an elliptical galaxy on the Fundamental Plane and calculate the stellar mass fraction inside $R_{Ein}$, and discuss the results with regards to the initial mass function.

• Journal of The Korean Astronomical Society
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• v.36 no.3
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• pp.75-80
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• 2003

When a bright astronomical object (source) is gravitationally lensed by a foreground mass (lens), its image appears to be located at different positions. The lens equation describes the relations between the locations of the lens, source, and images. The lens equation used for the description of the lensing behavior caused by a lens system composed of multiple masses has a form with a linear combination of the individual single lens equations. In this paper, we examine the validity of the linear nature of the multi-lens equation based on the general relativistic point of view.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.89.2-89.2
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• 2012

We present our analysis of a newly discovered galaxy-galaxy gravitational lens system in the First Look Survey (FLS) field. This object shows a highly distorted background galaxy (z=0.245) image by a nearby elliptical galaxy (z=0.08), which can be interpreted as a result of gravitational lensing. We model the lens with elliptical isothermal sphere model, and present the mass and potential distribution of the system.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.34-34
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• 2014

We investigate the constraints on the matter density ${\Omega}m$ and the cosmological constant ${\Omega}{\Lambda}$ using the gravitational lensed QSO (Quasi Stellar Object) systems from the Sloan Digital Sky Survey (SDSS) by analyzing the distribution of image separation. The main sample consists of 16 QSO lens systems with measured source and lens redshifts. We use a lensing probability that is simply defined by the gaussian distribution. We perform the curvature test and the constraints on the cosmological parameters as the statistical tests. The statistical tests have considered well-defined selection effects and adopt parameter of velocity dispersion function. We also applied the same analysis to Monte-Carlo generated mock gravitational lens samples to assess the accuracy and limit of our approach. As the results of these statistical tests, we find that only the excessively positively curved universe (${\Omega}m+{\Omega}{\Lambda}$ > 1) are rejected at 95% confidence level. However, if the informations of the galaxy as play a lens are measured accurately, we confirm that the gravitational lensing statistics would be the most powerful tool.

• Journal of The Korean Astronomical Society
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• v.36 no.3
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• pp.97-103
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• 2003

We now have more than 70 multiple image gravitational lens systems. Since gravitational lensing occurs through gravitational distortions in cosmic space, cosmological informations can be extracted from multiple image systems. Specifically, Hubble constant can be determined by the time delay mea-surement, curvature of the universe can be measured by the distribution of image separations in lens systems, and limits on matter density and cosmological constant can be set by the statistics of gravitationallens systems. Uncertainties, however, still exist in various steps, and results may be taken with some caution. Larger systematic survey and better understanding of galaxy properties would definitely help.