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- 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 46/122
451
- ISMAIL H. A.
- Journal of the Korean astronomical society = 천문학회지
- 38, n.1
- pp.7-12
- 2005
- 원문 바로보기
The frequency distribution of HII regions radii in our galaxy has been investigated. The correlation between the number of these regions and their radii has been re-determined, and could be represented by an exponential function. The size distribution of the HII regions in 10 spiral galaxies has been derived and combined with that of our galaxy to derive the distances of these galaxies. It has been found that the distances derived are in a good agreement with the published ones. The interstellar extinction in the galaxies has no influence on the distance estimate when using this geometrical method.
452
- Lee, Hye-Jin
- Journal of the Korean astronomical society = 천문학회지
- 38, n.3
- pp.345-355
- 2005
- 원문 바로보기
We present a photometric study of the star cluster system in the merging galaxy NGC 1487, based on the BI photometry obtained from the F450W and F814W images in the HST /WFPC2 archive data. We have found about 560 star cluster candidates in NGC 1487, using the morphological parameters of the objects. We have investigated several photometric characteristics of the clusters: color-magnitude diagrams (CMDs), color distribution, spatial distribution, age, size and luminosity function. The CMD of the bright clusters with 18.5 < B < 24 mag in NGC 1487 shows three major populations of clusters: a blue cluster population with <TEX>$(B-I){\le}0.45$</TEX>, an intermediate-color cluster population with <TEX>$0.45<(B-I){\le}1.55$</TEX>, and a red cluster population with (B - I) > 1.55. The intermediate-color population is the most dominant among the three populations. The brightest clusters in the blue and intermediate- color populations are as bright as <TEX>$B{\approx}18mag$</TEX> (<TEX>$M_B{\approx}-12mag$</TEX>), which are three magnitudes brighter than those in the red population. The blue and intermediate-color clusters are strongly concentrated on the bright condensations, while the red clusters are relatively more scattered over the galaxy. The CMD of these clusters is found to be remarkably similar to that of the clusters in the famous interacting system M51. From this we suggest that the intermediate-color clusters were, probably, formed during the merging process which occurred about 500 Myrs ago.
453
- CHAE JONGCHUL
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.295-298
- 2005
- 원문 바로보기
Recently a big progress has been made on the measurements of magnetic helicity of solar active regions based on photospheric magnetograms . In this paper, we present the details of Chae's method of determining the rate of helicity transfer using line-of-sight magnetograms such as taken by SORO /MDI. The method is specifically applied to full-disk magnetograms that are routinely taken at 96-minute cadence.
454
- 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.
455
- 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.
456
- 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.
457
- MATSUMOTO TOSHIO
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.89-91
- 2005
- 원문 바로보기
SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an infrared astronomical satellite with a 3.5 m cooled telescope which is very powerful in mid- and far- infrared observations and makes complementary role to JWST and Herschel. SPICA will be launched at ambient temperature without any cryogen into the Sun-Earth L2 orbit and cooled down in space to 4.5 K with use of efficient radiative cooling and mechanical coolers. The present status of SPICA and the developments of the satellite system are reported.
458
- 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.
459
- 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.
460
- MATSUMOTO TOSHIO
- Journal of the Korean astronomical society = 천문학회지
- 38, n.2
- pp.93-95
- 2005
- 원문 바로보기
ASTRO-F is the first Japanese dedicated infrared astronomical satellite which will be launched in 2005FY and is now in the final stage of the development. ASTRO-F is a 70 cm aperture cryogenically cooled telescope and designed for the infrared survey with much higher sensitivity and angular resolution than IRAS. We present the current status of the mission, focal plane instruments, and the observation plan now being discussed.