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1968년 ~ 2023년까지 1,187 건의 한국천문학회지를 격월간 확인하실 수 있습니다.
- The Korean Astronomical Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-4614 (ISSN : 1225-4614)
1225-4614
- DB구축현황 : 1,187건 (DB Construction : 1,187 Articles)
총 게시글 1,187건
페이지 49/119
481
- NISHIOKA HIROAKI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.175-178
- 2005
- 원문 바로보기
We show that next-generation galaxy surveys such as KAOS (the Kilo-Aperture Optical Spectro-graph)will constrain dark energy even if the baryon oscillations are missing from the monopole power spectrum and the bias is scale- and time-dependent KAOS will accurately measure the quadrupole power spectrum which gives the leading anisotropies in the power spectrum in redshift space due to peculiar velocities, the finger of God effect, as well as the Alcock-Paczynski effect. The combination of monopole and quadrupole power spectra powerfully breaks the degeneracy between the bias parameters and dark energy and, in the complete absence of baryon oscillations (<TEX>$\Omega$</TEX>b = 0), leads to a roughly <TEX>$500\%$</TEX> improvement in constraints on dark energy compared with the monopole spectrum alone. As a result, for KAOS the worst case with no oscillations has dark energy errors only mildly degraded relative to the ideal case, providing insurance on the robustness of KAOS constraints on dark energy. We show that nonlinear effects are crucial in correctly evaluating the quadrupole and significantly improving the constraints on dark energy when we allow for multi-parameter scale-dependent bias.
482
- Kyeong, Jae-Mann
- Journal of the Korean astronomical society = 천문학회지
- 38, n.4
- pp.415-422
- 2005
- 원문 바로보기
UBVIJHK photometry of the open cluster NGC 2194 are presented. Color-Magnitude diagrams of this cluster show well-defined main sequence and red giant clump. The main sequence also contains clear evidence of binary populations. Based on color-color diagrams, absolute magnitude of red giant clump, ZAMS fitting, and comparisons of observed color-magnitude diagrams with theoretical models, we derive following parameters for the cluster; reddening <TEX>$E(B-V)=0.44{\pm}0.04$</TEX>, age of log <TEX>$t{\sim}8.8$</TEX>, and finally distance of <TEX>$(m-M)_0=12.20{\pm}0.18$</TEX>.
483
- KIM SUNGEUN
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.223-226
- 2005
- 원문 바로보기
We present the results of a 21cm radio continuum aperture synthesis mosaic of the Large Magellanic Cloud (LMC), made by combining data from 1344 separate pointing centers using the Australia Telescope Compact Array (ATCA) and the 64-m Parkes single-dish telescope. The resolution of the mosaicked images is 55' ( 10 pc, using a distance to the LMC) and a region <TEX>$10^{\circ}{\times}12^{\circ}$</TEX> is surveyed.
484
- FENG LONG-LONG
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.129-133
- 2005
- 원문 바로보기
The temperature (T) and entropy (S) fields of baryonic gas, or intergalactic medium (IGM), in the ACDM cosmology are analyzed using simulation samples produced by a hybrid cosmological hydrodynamic/N-body code based on the weighted essentially non-oscillatory scheme. We demonstrate that, in the nonlinear regime, the dynamical similarity between the IGM and dark matter will be broken in the presence of strong shocks in the IGM. The heating and entropy production by the shocks breaks the IGM into multiple phases. The multiphase and non-Gaussianity of the IGM field would be helpful to account for the high-temperature and high-entropy gas observed in groups and clusters with low-temperature IGM observed by Ly<TEX>$\alpha$</TEX> forest lines and the intermittency observed by the spikes of quasi-stellar object's absorption spectrum.
485
- ELKHATEEB M. M.
- Journal of the Korean astronomical society = 천문학회지
- 38, n.1
- pp.13-16
- 2005
- 원문 바로보기
We present a period analysis of the well known <TEX>$\beta$</TEX> Lyrae type eclipsing binary GO Cyg <TEX>$(P= 0^d .7177)$</TEX>. Several new times of minimum light, recorded photoelectrically, have been gathered. Analysis of all available eclipse timings of GO Cyg has confirmed a significant period increase with rate of <TEX>$2.52 {\times} 10^{-10}$</TEX> day / cycle, also new period has been estimated. New linear and quadratic ephemerides have been calculated for the system.
486
- MULLER SEBASTIEN
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.245-248
- 2005
- 원문 바로보기
We present mm observations with the IRAM 30m radiotelescope of the HCN (J=1-0) and HCO+ (J=1-0) emission lines from Giant Moleculat Clouds (GMC) in the disk of the Andromeda Galaxy, The selected GMC targets have various morphology and environments, including locations within spiral arms or in interarm regions and with galactocentric radii ranging from 2.4 to 15.5 kpc over the disk. The radial distributions of the ratios HCN/CO and HCO+ /CO are discussed and their values are compared to other galaxies.
487
- MURATA YASUHIRO
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.97-100
- 2005
- 원문 바로보기
The first Space-VLBI project, VSOP, started successfully with the launch of the dedicated space-VLBI satellite HALCA in 1997. The project has been in scientific operation in the 1.6 GHz and 5 GHz bands, and studies have been done mainly of the jet phenomena related to active galactic nuclei. A second generation space- VLBI project, VSOP-2, has been planned by the working group formed at ISAS/JAXA with many collaborators. The spacecraft is planned to observe in the 8, 22 and 43 GHz bands with cooled receivers for the two higher bands, and with a maximum angular resolution at 43 GHz (7 mm) of about 40 micro-arcseconds. The VSOP-2 satellite will also have the capability of the phase-reference and full polarization observations, which will produce more powerful results than those of the VSOP project. Far-future space-VLBI projects following VSOP and VSOP-2, have a large potential to achieve enough resolution and sensitivity to satisfy astronomers in future.
488
- KO JONGWAN
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.149-151
- 2005
- 원문 바로보기
We have studied the environmental effect on optical-NIR color gradients of 273 nearby elliptical galaxies. Color gradient is a good tool to study the evolutionary history of elliptical galaxies, since the steepness of the color gradient reflects merging history of early types. When an elliptical galaxy goes through many merging events, the color gradient can be get less steep or reversed due to mixing of stars. One simple way to measure color gradient is to compare half-light radii in different bands. We have compared the optical and near infrared half-light radii of 273 early-type galaxies from Pahre (1999). Not surprisingly, we find that <TEX>$r_e(V)s$</TEX> (half-light radii measured in V-band) are in general larger than <TEX>$r_e(K)s$</TEX> (half-light radii measured in K-band). However, when divided into different environments, we find that elliptical galaxies in the denser environment have gentler color gradients than those in the less dense environment. Our finding suggests that elliptical galaxies in the dense environment have undergone many merging events and the mixing of stars through the merging have created the gentle color gradients.
489
- KOKUBO EUCHIRO
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.153-155
- 2005
- 원문 바로보기
We have developed the four-dimensional digital universe theater at which we can visualize the observational data and theoretical models of astronomical objects stereoscopically. The astronomical objects cover all scales of the universe from the solar system to the large-scale structure of the universe. We have also produced the three-dimensional movies of various astronomical processes based on the results of computer simulations. We plan to distribute all the products of this project through the internet.
490
- LEE JOUNGHUN
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.161-164
- 2005
- 원문 바로보기
We present a theoretical formalism by which the global and the local mass functions of dark matter substructures (dark subhalos) can be analytically estimated. The global subhalo mass function is defined to give the total number density of dark subhalos in the universe as a function of mass, while the local subhalo mass function counts only those sub halos included in one individual host halo. We develop our formalism by modifying the Press-Schechter theory to incorporate the followings: (i) the internal structure of dark halos; (ii) the correlations between the halos and the subhalos; (iii) the subhalo mass-loss effect driven by the tidal forces. We find that the resulting (cumulative) subhalo mass function is close to a power law with the slope of <TEX>${\~}$</TEX> -1, that the subhalos contribute approximately <TEX>$10\%$</TEX> of the total mass, and that the tidal stripping effect changes the subhalo mass function self-similarly, all consistent with recent numerical detections.