A5040954848- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Scientific Research and Discoveries
- Gamma-ray bursts and supernovae
- Adaptive optics and wavefront sensing
- Remote Sensing in Agriculture
- Impact of Light on Environment and Health
- History and Developments in Astronomy
- Solar and Space Plasma Dynamics
- Experimental and Theoretical Physics Studies
- Advanced Vision and Imaging
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Fluid Dynamics Simulations and Interactions
- Color Science and Applications
- Black Holes and Theoretical Physics
- Optical Polarization and Ellipsometry
- Plant Water Relations and Carbon Dynamics
- Soil and Environmental Studies
- Proteoglycans and glycosaminoglycans research
Pusan National University
2012-2024
University of Copenhagen
2011
The influence of a galaxy's environment on its evolution has been studied and compared extensively in the literature, although differing techniques are often used to define environment. Most methods fall into two broad groups: those that use nearest neighbours probe underlying density field fixed apertures. differences between inhibit clean comparison analyses leave open possibility that, even with same data, different properties actually being measured. In this work we apply twenty...
The morphological types of 5836 galaxies were classified by a visual inspection color images using the Sloan Digital Sky Survey Data Release 7 to produce morphology catalog representative sample local with . are almost complete for brighter than Our classification system is basically same as that Third Reference Catalog Bright Galaxies some simplifications giant galaxies. On other hand, we distinguish fine features dwarf elliptical (dE)-like classify five subtypes: dE, blue-cored...
Warped disks are almost ubiquitous among spiral galaxies. Here we revisit and test the "flyby scenario" of warp formation, in which impulsive encounters between galaxies responsible for warped disks. Based on N-body simulations, investigate morphological kinematical evolution stellar component when undergo flyby interactions with adjacent dark matter halos. We find that so-called "S"-shaped warps can be excited by flybys sustained even up to a few billion years, this scenario provides...
Bar fractions depend on the properties of host galaxies, which are closely related to formation and evolution bars. However, observational studies do not provide consistent results. We investigate bar fraction its dependence galaxies by using three classification methods: visual inspection, ellipse fitting method, Fourier analysis. Our volume-limited sample consists 1,698 spiral brighter than $M_{\rm r}=-15.2$ with $z < 0.01$ from SDSS/DR7 visually classified Ann et al. (2015). first compare...
view Abstract Citations (80) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Non-LTE Spectral Analysis and Model Constraints on SN 1993J Baron, E. ; Hauschildt, P. H. Branch, D. Austin, S. Garnavich, Ann, Hong Bae Wagner, R. M. Filippenko, A. V. Matheson, T. Liebert, James We present non-LTE synthetic spectra for a time series of observations obtained 1993 March 30-31, April 7, 13-15, June 13 UT. The are dominated by hydrogen Balmer lines;...
We have studied the radial distribution of early (E/S0) and late (S/Irr) types satellites around bright host galaxies. made a volume-limited sample 4,986 brighter than M_r = -18.0 associated with 2,254 hosts =-19.0 from SDSS DR5 sample. The morphology is determined by an automated classifier, but galaxies are visually classified. found segregation satellite as function projected distance galaxy. amplitude shape early-type fraction profile to depend on luminosity. This...
Abstract We explore the cosmic evolution of bar length, strength, and light deficit around for 379 barred galaxies at 0.2 < z ≤ 0.835 using F814W images from COSMOS survey. Our sample covers with stellar masses <?CDATA $10.0\leqslant \mathrm{log}({M}_{* }/{M}_{\odot })\leqslant 11.4$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>10.0</mml:mn> <mml:mo>≤</mml:mo> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow>...
We test the idea that bar pattern speeds decrease with time owing to angular momentum exchange a dark matter halo. If this process actually occurs, then locations of corotation resonance and other resonances should generally increase time. therefore derive velocity $\Omega$ epicyclic frequency $\kappa$ as functions galactocentric radius for 85 barred galaxies using photometric data. Mass maps are constructed by assuming dynamical mass-to-light ratio solving Poisson equation gravitatonal...
ABSTRACT Star formation histories (SFHs) are essential for understanding galaxy and evolution. We present the mean SFHs of 148 dwarf lenticular galaxies (dS0s) derived from Sloan Digital Sky Survey spectra. These reveal two distinct periods active star formation. The first period, concluding approximately 6 Gyr ago, witnessed predominantly old, metal-poor (Z = 0.0004) stars, accounting 60 per cent stellar mass 30 luminosity. scarcity extremely 0.0001) stars suggests pre-enrichment during...
We introduce a new approach to classify barred galaxies that utilizes the transverse-to-radial force ratio map (ratio map, hereafter) in different manner from previous studies. When we display polar coordinates, appear as four aligned, horizontal thick slabs. This characteristic feature enables us successfully and nonbarred with an accuracy of 87%. It yields bar fraction 53%, including both SBs SABs, when applied 884 nearby (z < 0.01) spiral Sloan Digital Sky Survey/DR7. also provides...
We have performed smoothed particle hydrodynamics (SPH) simulations for the response of gaseous disk to imposed moderately strong non-axisymmetric potentials. The model galaxies are composed three stellar components (disk, bulge and bar) two dark ones (supermassive black hole halo) whose gravitational potentials assumed be invariant in time frame corotating with bar. found that torques alone generated by bar gives maximum tangential-to-radial force ratio as $(F_{Tan}/F_{Rad})_{max}= 0.3$ not...
We present a wide field survey of satellite galaxies in M106 (NGC 4258) covering $1.7\degr \times 2\degr$ around using Canada-France-Hawaii Telescope/MegaCam. find 16 galaxy candidates M106. Eight these are found to be dwarf that much smaller and fainter than the remaining galaxies. Four new findings. Surface brightness profiles 15 out can represented well by an exponential disk profile with varying scale length. derive surface number density distribution The central (d $<100$ kpc) is...
We have initiated a long-term project, the BOAO photometric survey of open clusters, to enlarge our understanding Galactic structure using UBVI CCD photometry which been little studied before. This is second paper in we present 12 clusters. determined cluster parameters by fitting Padua isochrones color-magnitude diagrams All clusters except for Be 60 and NGC 1348 are found be intermediate-age old (0.2–4.0 Gyrs) with mean metallicity [Fe/H] ≈ 0.0.
We studied the structure of two old open clusters, NGC 1245 and 2506, from a wide deep VI photometry data acquired using CFH12K CCD camera at CFHT. devised new method for assigning cluster membership probability to individual stars both spatial positions in colour-magnitude diagram. From analyses luminosity functions several cluster-centric radii radial surface density profiles derived with different ranges, we found that clusters are dynamically relaxed drive significant mass segregation...
We have performed smoothed particle hydrodynamics (SPH) simulations to study the response of central kiloparsec region a gaseous disk imposition nonaxisymmetric bar potentials. The model galaxies are composed three axisymmetric components (halo, disk, and bulge) non-axisymmetric bar. These assumed be invariant in time frame corotating with potential spherical $\gamma$-models Dehnen is adopted for bulge component whose density varies as $r^{-\gamma}$ near center $r^{-4}$ at larger radiiand...
We analyze the spiral structure of 1725 nearby galaxies with redshift less than 0.02. use color images provided by Sloan Digital Sky Survey. determine arm classes (grand design, multiple-arm, flocculent) and broad Hubble types (early, intermediate, late) as well bar (SA, SAB, SB) visual inspection. find that flocculent are mostly late type while multiple-arm likely to be early type. The fractional distribution grand design is nearly constant along dependence class on not strong However,...
We have performed Smoothed Particle Hydrodynamic (SPH) simulations to study the response of molecular clouds in Galactic disk a rotating bar and their subsequent evolution Center (GC) region. The potential our models is contributed by three axisymmetric components (massive halo, exponential disk, compact bulge) non-axisymmetric bar. These are assumed be invariant time frame corotating with Some noticeable features such as an elliptical outer ring, spiral arms, gas-depletion region, central...
We study the behavior of galactic disks in triaxial halos both numerically and analytically to see if warps can be excited sustained potentials. consider following two scenarios: (1) that are initially tilted relative equatorial plane halo (for a pedagogical purpose), (2) infall dark matter disk halo. With numerical simulations 100,000 particles fixed potential, we find halos, just as spherical or axisymmetric but they show some oscillatory even transformed polar-ring system has prolate-like...
Optical spectra covering the region 5500 to 7000 A with a resolution of 2.1 were obtained during first visual -maximum supernova 1993J. Thirteen recorded between March 30.2 and 31.5 (UT). They show narrow emission features hydrogen, helium, highly ionized iron. The Hα line appears P-Cygni profile its width decreases observing interval. All sharp lines rapid drop in flux which can be attributed circumstellar gas being overtaken by expanding envelope. Supplementing our data taken Isaac Newton...
Time-series CCD photometric observations of an intermediate age open cluster NGC 2301 were performed to search for variable stars, particularly γ Dor stars and δ Sct stars. We also carried out UBVI photometry study physical properties in the cluster. derived observational parameters from results. The best fit empirical ZAMS a color-color diagram gives reddening value . estimated distance modulus , isochrone fitting color-magnitude diagram. Using V time-series data, we carefully examined...
We have conducted VI CCD photometry of the two open clusters NGC 1245 and 2506 using CFH12K camera. Our covers a sky area 84'X82' 42'X81' for clusters, respectively, reaches down to V = 23. derived physical parameters detailed theoretical isochrone fittings 2 minimization. The cluster are E(B-V) 0.24+/-0.05 0.03+/-0.04, (V-M_V)_0 12.25+/-0.12 12.47+/-0.08, age(Gyr) 1.08+/-0.09 2.31+/-0.16, [Fe/H]= -0.08+/-0.06 -0.24+/-0.06, respectively 2506, present luminosity functions (LFs) which reach...
We conducted a survey of open clusters within 1 kpc from the Sun using astrometric and photometric data Gaia Data Release 2. found 655 cluster candidates by visual inspection stellar distributions in proper motion space spatial l-b space. All have well defined main-sequence except for two if we consider that main sequence very young is somewhat broad due to differential extinction. Cross-matching our 653 with known various catalogs resulted 207 new clusters. present physical properties newly...
We present the star formation histories (SFHs) of early-type dwarf galaxies, dSphs and dEs, in local universe within z=0.01. The SFHs galaxies are characterized by pre-enriched, metal-poor old stellar populations, absence moderately stars that have ages a few Gyr. There some differences dEs. In particular, formed ($\gtrsim10$ Gyr old) $\sim2$ times more than effects reionization feedback from supernova explosions thought to be strong enough remove gas left, which prevent populations dSphs....