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1968년 ~ 2024년까지 1,211 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 : 1,211건 (DB Construction : 1,211 Articles)
총 게시글 1,211건
페이지 48/122
471
- 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.
472
- MAKINO JUNICHIRO
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.165-168
- 2005
- 원문 바로보기
We overview the GRAPE (GRAvity piPE) project. The goal of the GRAPE project is to accelerate the astrophysical N-body simulations. Since almost all computing time is spent for the evaluation of the gravitational force between particles, we can greatly accelerate many N-body simulations by developing a specialized hardware for the force calculation. In 1989, the first such hardware, GRAPE-1, was completed, with the peak speed of 120 Mflops. In 2003, GRAPE-6 was completed, with the peak speed of 64 Tflops, which is nearly 106 times faster than GRAPE-l and was the fastest computer at that time. In this paper, we review the basic concept of the GRAPE hardwares, the history of the GRAPE project, and two ongoing projects, GRAPE-DR and Project Milkyway.
473
- 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.
474
- 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.
475
- KOMIYA ZEN
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.157-160
- 2005
- 원문 바로보기
To constrain the values of the model parameters for the cosmological models involving the time-decaying <TEX>$\Lambda$</TEX> term, we have computed sets of theoretical predictions for the N-m relation of galaxies as well as the CMB angular power spectrum: three types of variation, viz., <TEX>${\Lambda}{\propto} T^{-1},\;a^{-m}$</TEX>, and <TEX>$H^n$</TEX> are thereby assumed following Overduin & Cooperstock (1998), although we concentrate here on the discussion of the results obtained from the first type. Our results for the N-m relation indicate that the observed excess of the galaxy counts N in the faint region beyond the blue apparent magnitude 24 can be reasonably well accounted for with the value of <TEX>${\iota}$</TEX> in the range between 0.2 and 1. Furthermore, a comparison of our computational results of the CMB spectra with the observational data shows that the models with a mild degree of the <TEX>$\Lambda$</TEX> term decay, viz., with the value of <TEX>${\iota}{\le}$</TEX>0.4, are favorable. In this case, the age of our universe turns out to be larger than or equal to 14 Gyr, the lower limit inferred from some Uranium datings.
476
- WEI Y
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.291-293
- 2005
- 원문 바로보기
Using 13.7 m telescope of Qinghai station of NAO, PMO at Delin Ha, 43 IRAS sources were mapped with <TEX>$^{13}CO\;J=1-0\;C^{18}O\;J=1-0$</TEX> and CO J=1-0. Each source has one or more cores. The distances of these cores range from 1 pc to several pc, and the masses from <TEX>$10^2\;M_{\bigodot}$</TEX> to <TEX>$10^5\;M_{\bigodot}$</TEX>. High velocity outflows were detected. The mass, momentum and energy of these massive cores are larger than those of the low mass ones. With radio, IRAS, MSX data, stellar source distribution were investigated, and sourceless cores that deviate from infrared sources were identified. They are potential high mass star formation sites.
477
- SAKA TAKESHI
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.253-256
- 2005
- 원문 바로보기
We have constructed the Mount Fuji submillimeter-wave telescope at Nishiyasugawara (alt. 3725 m) near the summit of Mt. Fuji (alt. 3774 m). Thanks to the excellent condition of Mt. Fuji, we have successfully carried out the [CI] survey toward more than 40 square degrees of sky, including qrion MC, Taurus MC, Rosetta MC, DR 15, DR 21, NGC 1333, NGC 2264, W 3, W 44, W 51, L 134, p-Oph. Our [CI] survey have revealed that the [CI] 492 GHz emission widely extends to the molecular clouds. The spatial and velocity structures of the [CI] 492 GHz emission resemble those of 13CO J=l-0 in many molecular clouds, implying that [CI] 492 GHz and <TEX>$^{13}CO$</TEX> J=1-0 are emitted from the same gas. The column density of <TEX>$C^o$</TEX> linearly correlates with that of CO up to high Av, suggesting that <TEX>$C^o$</TEX> exist in the deep interior of molecular clouds. In several regions, we have found that the distributions of <TEX>$C^o$</TEX> and CO are different from each other. The <TEX>$C^o$</TEX>-rich area is found in the Hieles' cloud 2. The C+/CO/<TEX>$C^o$</TEX> configuration is found in DR 15, p-Oph, M 17, Orion KL, and NGC 1333. These results indicate that an origin of <TEX>$C^o$</TEX> is unrelated with the photodissociation process. We discuss the observed <TEX>$C^o$</TEX> distributions in relation to the non-equilibrium chemistry.
478
- PYO TAE-SOO
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.249-252
- 2005
- 원문 바로보기
We present results of the velocity-resolved spectroscopy of the [Fe II] <TEX>$\lambda$</TEX>1.644<TEX>${\mu}m$</TEX> emission toward outflow sources with the Subaru Telescope at the angular resolution of 0.apos;16 <TEX>${\~}$</TEX> 0.apos;5 arcseconds. The observed sources are L1551 IRS 5, DG Tau, HL Tau and RW Aur, which are located in the Taurus-Aurigae Molecular Cloud, one of the closest star forming regions (0.apos;1 = 14 AU). We were able to resolve outflow structure in the vicinity of the sources at a scale of a few tens of AU. The position-velocity diagram of each object shows two velocity components: the high velocity component (HVC: 200 - 400 km <TEX>$s^{-l}$</TEX>) and the low velocity component (LVC: 50 - 150 km <TEX>$s^{-l}$</TEX>), which are clearly distinct in space and velocity. The HVC may be a highly collimated jet presumed from its narrow velocity width and high velocity. The LVC, on the other hand, may be a widely opened disk wind inferred from its broad velocity width and low velocity. The spectrum taken perpendicular to the L1551 IRS 5 outflow at its base shows that the LVC has a spatially wide subcomponent, supporting the above interpretation. We demonstrated that the [Fe II] 1.644 <TEX>$\mu$</TEX> spectroscopy is a very powerful tool for the studies of fast jets and winds that directly emanate from star-disk systems.
479
- SAWADA-SATOH SATOKO
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.183-186
- 2005
- 원문 바로보기
We present results of the VLBA observation toward the radio continuum and water maser emissions in a nearby LINER galaxy NGC 1052. The jet structure observed in 2000 is similar to that in 1998, and the two jet structures in 1998 and 2000 support the sub-luminal motion with apparent velocity of 0.26c. Distribution of water maser spots are located <TEX>${\~}$</TEX>0.05 pc shifted to southwest from the component which is supported to be the nucleus, and no rapid positional change of the water maser gas with respect to the central engine is seen from 1995 to 2000. The maser gas is positionally coincident with a plasma torus, and the position of the maser gas relative to the nucleus is stable from 1995 to 2000. The maser gas in NGC 1052 could be explained to be associated with the nuclear circumnuclear torus or disk like the situation found in the nucleus of NGC 4258.
480
- HwangBo, J.E.
- Journal of the Korean astronomical society = 천문학회지
- 38, n.4
- pp.437-443
- 2005
- 원문 바로보기
The Solar Radio Burst Locator (SRBL) is a spectrometer that can observe solar microwave bursts over a wide band (0.1-18 GHz) as well as detect the burst locations without interferometry or mechanical scanning. Its prototype has been operated at Owens Valley Radio Observatory (OVRO) since 1998. In this study, we have evaluated the capability of the SRBL system in flux and radio burst location measurements. For this, we consider 130 microwave bursts from 2000 to 2002. The SRBL radio fluxes of 53 events were compared with the fluxes from USAF/RSTN and the burst locations of 25 events were compared with the optical flare locations. From this study, we found: (1) there is a relatively good correlation (r = 0.9) between SRBL flux and RSTN flux; (2) the mean location error is about 8.4 arcmin and the location error (4.7 arcmin) of single source events is much smaller than that (14.9 arcmin) of multiple source events; (3) the minimum location error usually occurred just after the starting time of burst, mostly within 10 seconds; (4) there is a possible anti-correlation (r = -0.4) between the pointing error of SRBL antenna and the location error. The anti-correlation becomes more evident (r=-0.9) for 6 strong single source events associated with X-class flares. Our results show that the flux measurement of SRBL is consistent with that of RSTN, and the mean location error of SRBL is estimated to be about 5 arcmin for single source events.