간행물
천문학회지 KCI 등재 SCOPUS Journal of The Korean Astronomical Society
- 발행기관 한국천문학회
- 자료유형 학술지
- 간기 반년간
- ISSN 1225-4614 (Print)2288-890X (Online)
- 수록기간 1968 ~ 2024
- 주제분류 자연과학 > 천문학 자연과학 분류의 다른 간행물
- 십진분류KDC 440DDC 520
권호리스트/논문검색
제35권 제2호 (2002년 6월) 5건
1.
2002.06
구독 인증기관 무료, 개인회원 유료
We have made a topological study of cosmic microwave background (CMB) polarization maps by simulating the AMiBA experiment results. A ACDM CMB sky is adopted to make mock interferometric observations designed for the AMiBA experiment. CMB polarization fields are reconstructed from the AMiBA mock visibility data using the maximum entropy method. We have also considered effects of Galactic foregrounds on the CMB polarization fields. The genus statistic is calculated from the simulated Q and U polarization maps, where Q and U are Stokes parameters. Our study shows that the Galactic foreground emission, even at low Galactic latitude, is expected to have small effects on the CMB polarization field. Increasing survey area and integration time is essential to detect non-Gaussian signals of cosmological origin through genus measurement.
4,000원
2.
2002.06
구독 인증기관 무료, 개인회원 유료
We present N-body simulations of globular clusters including gravitational field of the Galaxy, in order to study effects of tidal field systematically on the shape of outer parts of globular clusters using NBODY6. The Galaxy is assumed to be composed of central bulge and outer halo. We mvestigate the cluster of multi-mass models with a power-law initial mass function (IMF) starting with different initial masses, initial number of particles, different slopes of the IMF and different orbits of the cluster. We have examined the general evolution of the clusters, the shape of outer parts of the clusters, density profiles and the direction of tidal tails. The density profiles appear to become somewhat shallower just outside the tidal boundary consistent with some observed data. The position angle of the tidal tall depends on the location in the Galaxy as well as the direction of the motion of. clusters. We found that the clusters become more elongated at the apogalacticon than at the pengalacticon. The tidal tails may be used to trace the orbital paths of globular clusters.
4,200원
3.
2002.06
구독 인증기관 무료, 개인회원 유료
We have conducted VI CCD photometry of the open cluster NGC 6819 in order to understand the effects of dynamical evolution in old open clusters. Our photometry covers 18'× 18' on the sky, centered on the cluster, which seems to cover the whole cluster field. Our photometry reaches down to V ≈ 20.5, which allows us to analyze the luminosity function and spatial distribution of stars brighter than Mv ≈ 8.5. There is a clear evidence for mass segregation in NGC 6819, i.e., the giants and upper main-sequence stars are concentrated in the inner regions, whereas the lower main-sequence stars distribute almost uniformly throughout the cluster. The luminosity function of the main-sequence stars of NGC 6819 is almost flat. The flat luminosity function indicates that a large number of low mass stars has escaped from the cluster unless its initial mass function is much different from the Salpeter type (Φ(m)∝ m-(1+x),x = 1.35).
4,000원
4.
2002.06
구독 인증기관 무료, 개인회원 유료
We have mapped 1 deg2 region toward a high latitude cloud MBM 40 in the J = 1 - 0 transition of 12CO and 13CO, using the 3 mm SIS receiver on the 14 m telescope at Taeduk Radio Astronomy Observatory. We used a high resolution autocorrelator to resolve extremely narrow CO linewidths of the molecular gas. Though the linewidth of the molecular gas is very narrow (FWHP < 1 km s-1), it is found that there is an evident velocity difference between the middle upper part and the lower part of the cloud. Their spectra for both of 12CO and 13CO show blue wings, and the position-velocity map shows clear velocity difference of 0.4 km s-1 between two parts. The mean velocity of the cloud is 3.1 km s-1. It is also found that the linewidths at the blueshifted region are broader than those of the rest of the cloud. We confirmed that the visual extinction is less than 3 magnitude, and the molecular gas is translucent. We discussed three mass estimates, and took a mass of 17 solar masses from CO integrated intensity using a conversion factor 2.3 × 10 20 cm -2 (K km s-1)-1. Spatial coincidence and close morphological similarity is found between the CO emission and dust far-infrared (FIR) emission. The ratio between the 100 f.Lm intensity and CO integrated intensity of MBM 40 is 0.7 (MJy/sr)/(K km s-1), which is larger than those of dark clouds, but much smaller than those of GMCs. The low ratio found for MBM 40 probably results from the absence of internal heating sources, or significant nearby external heating sources.
4,000원
5.
2002.06
구독 인증기관 무료, 개인회원 유료
We present the results of VLA NH3 (1,1) and (2,2) line observations of the young-stellar object (YSO) IRAS 19550+3248. The integrated intensity map of the NH3 (1,1) line shows that there are two ammonia cores in this region; core A which is associated with the YSO, and core B which is diffuse and located at the northeast of core A. Core A is compact and elongated along the east-west direction (0.07 pc×0.05 pc) roughly perpendicular to the molecular outflow axis. Core B is diffuse and extended (0.18 pc×0.07 pc). NH3 (2,2) line is detected only toward core A, which indicates that it is hotter (~ 15 K), presumably due to the heating by the YSO. The NH3 (1,1) line toward core A is wide (Δv ≳ 3 km s-l) and appears to have an anomalous intensity ratio of the inner satellite hyperfine lines. The large line width may be attributed to the embedded YSO, but the hyperfine anomaly is difficult to explain. We compare the results of NH3 observations with those of previous CS observations and find that the CS emission is detected only toward core A and is much more extended than the NH3 emission.
4,000원
