• 천문학회보
• /
• 제46권1호
• /
• pp.35.2-35.2
• /
• 2021

Blue straggler stars (BSs) are "rejuvenated" main sequence stars first recognized by Allan Sandage from his observation of the prominent northern globular cluster M3 in the year of 1953. BSs are now known to be present in diverse stellar environments including open clusters, globular clusters, dwarf galaxies, and even the field populations of the Milky Way. This makes them a very useful tool in a wide range of astrophysical applications: Particularly BSs are considered to have a crucial role in the evolution of stellar clusters because they affect on the dynamics, the binary population, and the history of the stellar evolution of the cluster they belong to. Here we report a part of the preliminary results from our ongoing research on the BSs in the two metal-poor globular clusters (GCs) in the Large Magellanic Cloud (LMC), Hodge 11 and NGC1466. Using the high precision multi-band images obtained with the Advanced Camera for Survey (ACS) onboard the Hubble Space Telescope (HST), we extract time-series photometry to search for the signal of periodic variations in the luminosity of the BSs. Our preliminary results confirm that several BSs are intrinsic "short period (0.05 < P < 0.25 days)" variable stars with either pulsating or eclipsing types. We will discuss our investigation on the properties of those variable BS candidates in the context of the formation channels of these exotic main sequence stars, and their roles in the dynamical evolution of the host star clusters.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
• /
• pp.237-240
• /
• 2005

Calibration and Validation are major element of any space borne Earth Observation Mission. These activities are the major objective of the commissioning phases but routine activities shall be maintained during the whole mission in order to maintain the quality of the product delivered to the users or at least to fully characterise the evolution with time of the product quality. With the launch of ERS-l in 1991, the European Space Agency decided to put in place a group dedicated to these activities, along with the daily monitoring of the product quality for anomaly detection and algorithm evolution. These four elements are all strongly linked together. Today this group is fully responsible for the monitoring of two ESA missions, ERS-2 and Envisat, for a total of 12 instruments of various types, preparing itself for the Earth Explorer series of five. other satellites (Cryosat, Goce, SMOS, ADM-Aeolus, Swarm) and at various levels in past and future Third Party Missions such as Landsat, J-ERS, ALOS and KOMPSAT. The Joint proposal by the European Union and the European Space Agency for a 'Global Monitoring for Environment and Security' project (GMES), triggers a review of the scope of these activities in a much wider framework than the handling of single missions with specific tools, methods and activities. Because of the global objective of this proposal, it is necessary to put in place Multi-Mission Calibration and Validation systems and procedures. GMES Calibration and Validation activities will rely on multi source data access, interoperability, long-term data preservation, and definition standards to facilitate the above objectives. The scope of this presentation is to give an overview of the current Calibration and Validation activities at ESA, and the planned evolution in the context of GMES.

• 천문학회보
• /
• 제44권1호
• /
• pp.78.2-78.2
• /
• 2019

We develop an Alcock-Paczynski (AP) test method that uses the evolution of redshift-space two-point correlation function (2pCF) of galaxies. The method improves the AP test proposed by Li et al. (2015) in that it uses the full two-dimensional shape of the correlation function. Similarly to the original method, the new one uses the 2pCF in redshift space with its amplitude normalized. Cosmological constraints can be obtained by examining the redshift dependence of the normalized 2pCF. This is because the 2pCF should not change apart from the expected small non-linear evolution if galaxy clustering is not distorted by incorrect choice of cosmology used to convert redshift to comoving distance. Our new method decomposes the redshift difference of the 2-dimensional correlation function into the Legendre polynomials whose amplitudes are modelled by radial fitting functions. The shape of the normalized 2pCF suffers from small intrinsic time evolution due to non-linear gravitational evolution and change of type of galaxies between different redshifts. It can be accurately measured by using state of the art cosmological simulations. We use a set of our Multiverse simulations to find that the systematic effects on the shape of the normalized 2pCF are quite insensitive to change of cosmology over \Omega_m=0.21 - 0.31 and w=-0.5 - -1.5. Thanks to this finding, we can now apply our method for the AP test using the non-linear systematics measured from a single simulation of the fiducial cosmological model.

• 천문학회보
• /
• 제45권1호
• /
• pp.65.3-66
• /
• 2020

We use the IllustrisTNG cosmological hydrodynamical simulation to study the evolution of star formation rate (SFR)-density relation over cosmic time. We construct several samples of galaxies at different redshifts from z=2.0 to z=0.0, which have the same comoving number density. The SFR of galaxies decreases with local density at z=0.0, but its dependence on local density becomes weaker with redshift. At z≳1.0, the SFR of galaxies increases with local density (reversal of the SFR-density relation), and its dependence becomes stronger with redshift. This change of SFR-density relation with redshift still remains even when fixing the stellar masses of galaxies. The dependence of SFR on the distance to a galaxy cluster also shows a change with redshift in a way similar to the case based on local density, but the reversal happens at a higher redshift, z~1.5, in clusters. On the other hand, the molecular gas fraction always decreases with local density regardless of redshift at z=0.0-2.0 even though the dependence becomes weaker when we fix the stellar mass. Our study demonstrates that the observed reversal of the SFR-density relation at z≳1.0 can be successfully reproduced in cosmological simulations. Our results are consistent with the idea that massive, star-forming galaxies are strongly clustered at high redshifts, forming larger structures. These galaxies then consume their gas faster than those in low-density regions through frequent interactions with other galaxies, ending up being quiescent in the local universe.

• 한국실내디자인학회논문집
• /
• 제22권3호
• /
• pp.100-107
• /
• 2013

In smart era, concept of User experience has been an important issue both in academic and practical areas in recent years. Interactive space became one of the major design paradigms. For elevating the interactive effect, we need user?centered design methodology which uses the influential factors on the interactivity. As, well developed information technology made a lot of changes to various fields of our society, interactive space with the concept of HCI became a big issue in environmental design field. In this interactive space, various types of informative factors of the given space are sent using sensor and computer networking technology to the main system. So, a user's movement in the space in more than just a movement itself-user's movement now forms a important spatial structure that leads the narrative of the space. in this research, I will come up with the problems that the interactive space has right now, and analyze what the public space must have, and combine them with interactive space by HCI theory. architecture space is not the old space adapting digital technology. In order to take the role as new space paradigm. environment and technology, it has to develop technology continuously and experimental space at the same time. It must have co-evolution of architecture space field and others through organic network. by that, the evolution of space will be in the way that combines space which is responded to human emotion and user centric human friendly.

• 한국실내디자인학회논문집
• /
• 제21권3호
• /
• pp.50-57
• /
• 2012

In Ubiquitous era. architecture is not the old building adapting ubiquitous technology. In order to take the role as new architectural paradigm in space, environment and technology, it has to develop technology continuously and experimental architecture at the same time. it must have co-evolution of architectural field and others through organic network. by that, the evolution of space will be in the way that combines space which is responded to human emotion and user-centric human-friendly. It will be the new paradigm of Ubiquitous digital space. Digital technology resulted in a change to a society as well as to the life of human and its way of thinking. Due to those changes, new terms or concepts come out and a new meaning is added to the conventional concepts. This aims to examine type of spatial contexts for interaction design experience. This study is performed through Literature research for theory by interactive space and case studies for construction elements to design. The range of case study is limited to interaction space in addition of interactive elements and user interface. And analysis conclusion is show the many type, First, Interactive space has special purpose for make a interaction by intelligent elements.(sensor, program, algorithm, New-technology) Second, Interactive space was cooperation with various professional for space purpose. Third. Interactive space is self-develop by algorithm, program, sensor network and that is harmonize with user. finally. Interaction space is show the temper elements about allness, metastatic, activeness, liquidity, relationship. That was written by ecological theory.

• 천문학회지
• /
• 제47권3호
• /
• pp.87-98
• /
• 2014

We develop a parallel cosmological hydrodynamic simulation code designed for the study of formation and evolution of cosmological structures. The gravitational force is calculated using the TreePM method and the hydrodynamics is implemented based on the smoothed particle hydrodynamics. The initial displacement and velocity of simulation particles are calculated according to second-order Lagrangian perturbation theory using the power spectra of dark matter and baryonic matter. The initial background temperature is given by Recfast and the temperature uctuations at the initial particle position are assigned according to the adiabatic model. We use a time-limiter scheme over the individual time steps to capture shock-fronts and to ease the time-step tension between the shock and preshock particles. We also include the astrophysical gas processes of radiative heating/cooling, star formation, metal enrichment, and supernova feedback. We test the code in several standard cases such as one-dimensional Riemann problems, Kelvin-Helmholtz, and Sedov blast wave instability. Star formation on the galactic disk is investigated to check whether the Schmidt-Kennicutt relation is properly recovered. We also study global star formation history at different simulation resolutions and compare them with observations.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
• /
• pp.38.3-39
• /
• 2010

While major solar proton events (SPEs) come from the coronal mass eject (CME)-driven shocks in solar wind, there are many evidences that potentiality of CMEs to generate SPEs depends on its early evolution near the Sun and on different solar activities observed around the CME liftoff time. To decipher origin of SPE release, we have investigated onset time comparison of the SPE with CME, metric type II radio burst, and hard X-ray flare. For this, we select 30 SPEs observed from 1997 to 2006 by using the particle instrument ERNE onboard SOHO, which allows proton flux anisotropy measurement in the energy range ~10 - 50MeV. Onset time of the SPEs is inferred by considering the energy-dependent proton transport time. As results, we found that (1) SPE onset time is comparable to that of type II but later than type III onset time and HXR start time, (2) SPE onset time is mostly later than the peak time of HXR flare, (3) almost half of the SPE onsets occurred after the HXR emission, and (4) there are two groups of CME height at the onset time of SPE; one is the height below 5 Rs (low corona) and the other is above 5Rs (high corona). In this talk, we will present the onset time comparison and discuss about the origin of the SPE onset.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
• /
• pp.51-51
• /
• 2004

• 천문학회보
• /
• 제38권2호
• /
• pp.49.2-49.2
• /
• 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.