• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.2
• /
• pp.76.2-76.2
• /
• 2011

It is widely accepted that the SED of a galaxy relates to its morphology. In addition, the SED of the galaxy is closely connected to its star formation history, and its morphological properties are affected by the merger history, interactions with its environment, and the gravitational instability of its dynamical system. Thus, it is likely that star formation history correlates to the elements that determine morphological properties. Among the elements, this study investigates how much the merger histories of galaxies influence their star formation histories. By using simple merger trees and semi-analytic models, which disregard feedback processes to exclusively identify merger effects on star formation histories, we examine the relation between various merger histories and SEDs of galaxies. From the results, we discuss whether the SED of a galaxy can represent and constrain its merger history.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.1
• /
• pp.32.1-32.1
• /
• 2013

We use numerical simulations to investigate the evolution of both the star formation rate (SFR) and the observable properties of equal-mass disk merger remnants for 18 different orbital configurations. In our analysis, the photometric properties of the remnants have been constructed by considering dust reddening effect in order to facilitate the comparison with observational data of large surveys such as the Sloan Digital Sky Survey (SDSS). First, we found that the detailed evolutions of merging galaxies are different between the merging characteristics such as merging time scale, SFR history, and burst efficiency. Around $70{\pm}5$ percent of gas turns into stars until the merger-induced starburst ends regardless of merger types. Our study also suggests that merger features involve a small fraction of stars. Merger features last roughly 3 times the final coalescence time of galaxy mergers. For a shallower surface brightness limit, the features seem to survive in a shorter time, which is the reason why detecting merger features by using shallow surveys were difficult in the past.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.1
• /
• pp.33.2-33.2
• /
• 2014

Halo merger trees are essential backbones of semi-analytic models for galaxy formation and evolution. Recent studies have pointed out that extracting merger trees from numerical simulations of structure formation is non-trivial; different algorithm can give differing merger histories. Thus they should be carefully understood before being used as input for models of galaxy formation. As one of the projects proposed in the SUSSING MERGER TREES Workshop, we investigate the impact of different halo merger trees on a semi-analytic model. We find that the z = 0 global galaxy properties in our model show differences between trees when using a common parameter set, but that these differences are not very significant. However, the star formation history of the Universe and the properties of satellite galaxies can show marked differences between trees with different methods for constructing a tree. Calibrating the SAM for each tree individually to the empirical data can reduce the discrepancies between the z = 0 global galaxy properties, however this is at cost of increasing the differences in evolutionary histories of galaxies. Furthermore, the underlying physics implied can vary, resulting in key quantities such as the supernova feedback efficiency differing by factors of 2. Such a change alters the regimes where star formation is primarily suppressed by supernovae. Therefore, halo merger trees extracted from a common halo catalogue using different, but reliable, algorithms can result in a difference in the semi-analytic model, however, given the enormous uncertainties in galaxy formation physics, these are not necessarily significant.

• Publications of The Korean Astronomical Society
• /
• v.30 no.2
• /
• pp.473-474
• /
• 2015

Halo merger trees are the essential backbone of semi-analytic models for galaxy formation and evolution. Srisawat et al. (2013) show that different tree building algorithms can build different halo merger histories from a numerical simulation for structure formation. In order to understand the differences induced by various tree building algorithms, we investigate the impact of halo merger trees on a semi-analytic model. We find that galaxy properties in our models show differences between trees when using a common parameter set. The models independently calibrated for each tree can reduce the discrepancies between global galaxy properties at z=0. Conversely, with regard to the evolutionary features of galaxies, the calibration slightly increases the differences between trees. Therefore, halo merger trees extracted from a common numerical simulation using different, but reliable, algorithms can result in different galaxy properties in the semi-analytic model. Considering the uncertainties in baryonic physics governing galaxy formation and evolution, however, these differences may not necessarily be significant.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.2
• /
• pp.39.2-39.2
• /
• 2019

Diffuse radio emissions at the outskirt of merging galaxy clusters called radio relics provide a unique channel to understand the merger history. We present a recent discovery of double radio relics in the cluster merger ZwCL1447+2619 from our recent Giant Metrewave Radio Telescope observations. Both Band 3 (300-500 MHz) and Band 4 (550-850 MHz) data reveal a large (~1Mpc) and thin (~40kpc) radio relic ~1Mpc from the cluster X-ray center and a small radio relic (~0.3 Mpc) on the opposite side. These remarkable radio data together with Subaru weak-lensing analysis and Chandra X-ray observations enable us to reconstruct the merger scenario. Our preliminary analysis suggests that the cluster ZwCL J1447+2619 is a post-merger near its returning phase. In addition, using Keck DEIMOS spectroscopy, we find many "green" and "blue" member galaxies are located between the radio relics, a possible indication of merger shock-driven star formation activities.

• Management & Information Systems Review
• /
• v.23
• /
• pp.157-174
• /
• 2007

Concerning this nation's M&A system, it is expected that standards of limitation on ownership is considerably modified and alleviated. This would allow companies to freely merge with each other, raising the efficiency of the whole national economy and ultimately benefiting all economic subjects. Another goal of business merger lies in adjusting net income or reducing tax amount. The income and the amount are to be financially reported. If merger between companies does not create any synergy effect, but just contributes to net income increase or tax reduction for the purpose of the parties' financial reporting, it might distort a rational distribution of wealth over all facets of economy. Merger whose goal is to create the most desirable synergy effect should be positively encouraged, but that whose goal lies in tax avoidance needs to be strongly restricted. Thus the purpose of this study was to find how to improve this nation's merger-related taxation system. For the purpose, this researcher investigated problems of existing tax supports to merger, which meets related taxation requirements, especially in terms of liquidation income, appraisal profit from merger, fictitious dividend and requirements for taxation. Among the problems, the study found, the biggest thing was that liquidation income or deficit carried forward, if any, is subject to be prior deducted from surplus, so the income is likely to generate. To raise the consistency of this nation's taxation on business restructuring, existing local systems in regard to merger, division, investment in kind and dividend-exclusion method need to be reconsidered following the introduction of consolidated taxation system.

• Korean Journal of Social Welfare
• /
• v.37
• /
• pp.307-326
• /
• 1999

The primary purpose of this study is to analyze changes, if any, in the financial status and the intensity of health care service utilization of the regional health insurance societies following the 1995 merger of some rural and urban regional health insurance societies. Ultimately, this study is aiming at providing an empirical basis for predicting the impact of the 1998 merger of the Regional Health Insurance Program and the Health Insurance Program for Government Employees and Teachers and, further, predicting the impact of the merger of the entire health insurance programs scheduled for the year 2000. The study results did not suggest that the 1995 merger had brought about notable changes in the rate of increase in the total expenditures or the insurance payment of the merged regional insurance societies in comparison to non-merged ones. Neither did it show that the merger had resulted in significant changes in the intensity of the use of health services. The study, however, found that the 1995 merger had reduced the rate of increase in the management and operational cost of the merged insurance societies. Based on these findings, some policy implications are discussed, and suggestions are made for the total merger plan scheduled for the year 2000.

• Journal of The Korean Astronomical Society
• /
• v.37 no.5
• /
• pp.471-476
• /
• 2004

We propose an analytical model to estimate the influence of a merger on the thermal SZ effect. Following observations we distinguish between subsonic and transonic mergers. Using analytical velocity fields and the Bernoulli equation we calculate the excess pressure around a moving subcluster for an incompressible subsonic gas. Positive excess around the stagnation point and negative excess on the side of the subcluster lead to characteristic signatures in the SZ map, of the order of $10\%$ compared to the unperturbed signal. For a transonic merger we calculate the change in the thermal spectral SZ function, resulting from bow shock accelerated electrons. The merger shock compression factor determines the power law tail of the new non-thermal electron population and is directly related to a shift in the crossover frequency. This shift is typically a few percent towards higher frequencies.

• Journal of Information Technology Services
• /
• v.10 no.4
• /
• pp.67-81
• /
• 2011

Recently, Mergers and Acquisitions (M&A) have become increasingly popular in the last few decades, and overseas' M&A are particularly increasing to sharpen corporate competitiveness on a global scale. Previous studies showed that one of the main reasons attributes to failures of mergers was the lack of attention to merging information systems. In recent years, both academy and industry have more focused on Post-Merger Integration (PMI) and the integration of information systems (IS) between two companies is one of the critical success factors of corporate. This paper focused on Post-Merger IT (Information Technology) Integration Methodology of Cross-Border M&A. We followed a single-site qualitative case study method in order to investigate the type of phenomenon in M&A's natural setting. Moreover, we examined a typical energy and power company case in order-based industry, so that other industry players may have different results to determine post-merger IT integration method and scope.

• Speech Sciences
• /
• v.5 no.2
• /
• pp.41-55
• /
• 1999

This paper aims to acoustically analyze the merger of back vowels in North Korean dialects which I believe, are here investigated for the first time since 1945. North Korean back vowels are distinctive from South Korean back vowels because they merge mainly on the back vowel space, while front vowels merge mainly in Seoul standard language and other South Korean dialects. In this paper the future of the vowel systems caused by the merger of the vowels in Korean dialects will also be investigated. North Korean dialects examined include dialects of the Pyungan, the Hamkyung, and the Hwanghae Provinces. North Korean back vowels are distinctive from South Korean back vowels because they merge mainly on the back vowel space, while front vowels merge mainly in Seoul standard language and other South Korean dialects.