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한국천문학회지

1968년 ~ 2024년까지 1,211 건한국천문학회지를 격월간 확인하실 수 있습니다.

  • The Korean Astronomical Society (The Korean Astronomical Society)
  • 계간 (Quarterly)
  • ISSN : 1225-4614 (ISSN : 1225-4614)
  • DB구축현황 : 1,211건 (DB Construction : 1,211 Articles)
안내사항
총 게시글 1,211 페이지 3/122
21
  • Kim Dachan
  • Journal of the Korean Astronomical Society = 천문학회지
  • 57, n.1
  • pp.45-54
  • 2024
  • 원문 바로보기
The Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) will provide all-sky spectral survey data covering optical to mid-infrared wavelengths with a spatial resolution of 6.'2, which can be widely used to study galaxy formation and evolution. We investigate the galaxy-galaxy blending in SPHEREx datasets using the mock galaxy catalogs generated from cosmological simulations and observational data. Only ~0.7% of the galaxies will be blended with other galaxies in all-sky survey data with a limiting magnitude of 19 AB mag. However, the fraction of blended galaxies dramatically increases to ~7-9% in the deep survey area around the ecliptic poles, where the depth reaches ~22 AB mag. We examine the impact of the blending in the number count and luminosity function analyses using the SPHEREx data. We find that the number count can be overestimated by up to 10-20% in the deep regions due to the flux boosting, suggesting that the impact of galaxy-galaxy blending on the number count is moderate. However, galaxy-galaxy blending can marginally change the luminosity function by up to 50% over a wide range of redshifts. As we only employ the magnitude limit at K<sub>s</sub>-band for the source detection, the blending fractions determined in this study should be regarded as lower limits.
22
  • Sanghyeon Han
  • Journal of the Korean Astronomical Society = 천문학회지
  • 57, n.2
  • pp.249-259
  • 2024
  • 원문 바로보기
We examine whether the radial acceleration relation (RAR) of dwarf galaxies can be explained by Verlinde's emergent gravity. This is the extension of Yoon et al. (2023), which examine the RAR of typical spiral galaxies, to less massive systems. To do this, we compile the line-of-sight velocity dispersion profiles of 30 dwarf galaxies in the Local Group from the literature. We then calculate the expected gravitational acceleration from the stellar component in the framework of the emergent gravity, and compare it with that from observations. The calculated acceleration with the emergent gravity under the assumption of a quasi-de Sitter universe agrees with the observed one within the uncertainty. Our results suggest that the emergent gravity can explain the kinematics of galaxies without introducing dark matter, even for less massive galaxies where dark matter is expected to dominate. This sharply contrasts with MOND, where a new interpolating function has to be introduced for dwarf galaxies to explain their kinematics without dark matter.
23
  • Changmin Kim
  • Journal of the Korean Astronomical Society = 천문학회지
  • 57, n.1
  • pp.11-11
  • 2024
  • 원문 바로보기
The following sentence was erroneously dropped from the acknowledgment: This work was supported by Chungnam National University. The corrected text is listed below; it should replace the Acknowledgements section.
24
  • Yong-Jae Moon
  • Journal of the Korean Astronomical Society = 천문학회지
  • 57, n.1
  • pp.35-44
  • 2024
  • 원문 바로보기
The Sun-Earth Lagrange point L4, which is called a parking space of space, is considered one of the unique places where solar activity and the heliospheric environment can be observed continuously and comprehensively. The L4 mission affords a clear and wide-angle view of the Sun-Earth line for the study of Sun-Earth connections from remote-sensing observations. The L4 mission will significantly contribute to advancing heliophysics science, improving space weather forecasting capability, extending space weather studies far beyond near-Earth space, and reducing risk from solar radiation hazards on human missions to the Moon and Mars. Our paper outlines the importance of L4 observations by using remote-sensing instruments and advocates comprehensive and coordinated observations of the heliosphere at multi-points including other planned L1 and L5 missions. We mainly discuss scientific perspectives on three topics in view of remote sensing observations: (1) solar magnetic field structure and evolution, (2) source regions of geoeffective solar energetic particles (SEPs), and (3) stereoscopic views of solar corona and coronal mass ejections (CMEs).
25
  • Hyeonoh Hur
  • Journal of the Korean astronomical society = 천문학회지
  • 56, n.1
  • pp.97-115
  • 2023
  • 원문 바로보기
We present the deep homogeneous UBV RI photometric data of 135,071 stars down to V ~ 23 mag and I ~ 22 mag toward the Carina Nebula. These stars are cross-matched with those from the previous surveys in the X-ray, near-infrared, and mid-infrared wavelengths as well as the Gaia Early Data Release 3 (EDR3). This master catalog allows us to select reliable members and determine the fundamental parameters distance, size, stellar density of stellar clusters in this star-forming region. We revisit the reddening toward the nebula using the optical and the near-infrared colors of early-type stars. The foreground reddening [E(B-V)<sub>fg</sub>] is determined to be 0.35 &#x00B1; 0.02, and it seems to follow the standard reddening law. On the other hand, the total-to-selective extinction ratio of the intracluster medium (R<sub>V,cl</sub>) decreases from the central region (Trumpler 14 and 16, R<sub>V,cl</sub> ~ 4.5) to the northern region (Trumpler 15, R<sub>V,cl</sub> ~ 3.4). It implies that the central region is more dusty than the northern region. We find that the distance modulus of the Carina Nebula to be 11.9 &#x00B1; 0.3 mag (d = 2.4 &#x00B1; 0.35 kpc) using a zero-age main-sequence fitting method, which is in good agreement with that derived from the Gaia EDR3 parallaxes. We also present the catalog of 3,331 pre-main-sequence (PMS) members and 14,974 PMS candidates down to V ~ 22 mag based on spectrophotometric properties of young stars at infrared, optical, and X-ray wavelengths. From the spatial distribution of PMS members and PMS candidates, we confirm that the member selection is very reliable down to faint stars. Our data will have a legacy value for follow-up studies with different scientific purposes.
26
  • Alexey Rudnitskiy
  • Journal of the Korean astronomical society = 천문학회지
  • 56, n.1
  • pp.91-96
  • 2023
  • 원문 바로보기
In this paper, we describe the first multi-frequency synthesis observations of blazar 0059+581 made with the Radioastron space-ground interferometer in conjunction with the Korean VLBI Network (KVN), Medicina and Torun ground telescopes. We conducted these observations to assess the spaceground interferometer multi-frequency mode capability for the first time.
27
  • Tetsuya Magara
  • Journal of the Korean astronomical society = 천문학회지
  • 56, n.2
  • pp.225-229
  • 2023
  • 원문 바로보기
We investigated an emerging magnetic loop dynamically formed on the Sun, which has the effective footpoint heating source that may play a key role in heating a solar atmosphere with free magnetic energy in it. It is suggested that the heating source could be related to local compression of a plasma in the emerging loop by means of Lorentz force, which converts the magnetic energy to the internal energy of the plasma that is used to reaccelerate a decelerated downflow along the loop, eventually generating the source when the kinetic energy of the downflow is thermalized. By analyzing very high-cadense data obtained from a magnetohydrodynamic simulation, we demonstrate how the local compression is activated to trigger the generation of the heating source. This reveals a characteristic of the emerging loop that experiences a dynamic loop-loop interaction, which causes the local compression and makes the plasma gain the internal energy converted from the magnetic energy in the atmosphere. What determines the characteristic that could distinguish an illuminated emerging loop from a nonilluminated one is discussed.
28
  • Changmin Kim
  • Journal of the Korean astronomical society = 천문학회지
  • 56, n.1
  • pp.59-73
  • 2023
  • 원문 바로보기
The second generation of stars in the globular clusters (GCs) of the Milky Way (MW) exhibit unusually high N, Na, or Al, compared to typical Galactic halo stars at similar metallicities. The halo field stars enhanced with such elements are believed to have originated in disrupted GCs or escaped from existing GCs. We identify such stars in the metallicity range -3.0 < [Fe/H] < 0.0 from a sample of ~36,800 giant stars observed in the Sloan Digital Sky Survey and Large Sky Area Multi-Object Fiber Spectroscopic Telescope survey, and present their dynamical properties. The N-rich population (NRP) and N-normal population (NNP) among our giant sample do not exhibit similarities in either in their metallicity distribution function (MDF) or dynamical properties. We find that, even though the MDF of the NRP looks similar to that of the MW's GCs in the range of [Fe/H] < -1.0, our analysis of the dynamical properties does not indicate similarities between them in the same metallicity range, implying that the escaped members from existing GCs may account for a small fraction of our N-rich stars, or the orbits of the present GCs have been altered by the dynamical friction of the MW. We also find a significant increase in the fraction of N-rich stars in the halo field in the very metal-poor (VMP; [Fe/H] < -2.0) regime, comprising up to ~20% of the fraction of the N-rich stars below [Fe/H] = -2.5, hinting that partially or fully destroyed VMP GCs may have in some degree contributed to the Galactic halo. A more detailed dynamical analysis of the NRP reveals that our sample of N-rich stars do not share a single common origin. Although a substantial fraction of the N-rich stars seem to originate from the GCs formed in situ, more than 60% of them are not associated with those of typical Galactic populations, but probably have extragalactic origins associated with Gaia Sausage/Enceladus, Sequoia, and Sagittarius dwarf galaxies, as well as with presently unrecognized progenitors.
29
  • Sang-Hyeon Ahn
  • Journal of the Korean astronomical society = 천문학회지
  • 56, n.2
  • pp.137-147
  • 2023
  • 원문 바로보기
Shoushili was the official calendrical method promulgated in 1280 CE by the Yuan dynasty. It contains a list of the angular spans in right ascensions for the 28 lunar lodges. They are known to have been measured by Guo Shoujing with his advanced instruments with an unprecedented precision or reading error of 5'. Such precise data are useful to determine their observational epoch with an error range which is narrow enough to pinpoint on which historical occasion they were observed. Using the precise SIMBAD data based on eDR3 of GAIA and carefully identified determinative stars and considering the precession of equinoxes and proper motions, we apply linear regression methods to those data and obtain the observational epoch of 1271 &#x00B1; 16 CE and the measurement error of 4.1'. We also have polar distances corresponding to declinations written in another manuscript of the Ming dynasty. Since the two data sets have similar significant digits, they were suggested to have the same origin. However, we obtain their observational epoch of 1364&#x00B1;5 CE and the measurement error of 5.7'. They must have been measured with different instruments and on a different occasion from the observations related to Shoushili. We review the history of the calendrical reform during the 13th century in the Yuan dynasty. We conclude that the observational epoch obtained from lodge spans in Shoushili agrees with the period of observations led by Guo Shoujing or 1276-1279 CE, which is also supported by the fact that the ecliptic lodge span values listed in Shoushili were calculated from the equatorial lodge spans.
30
  • Byeong-Cheol Lee
  • Journal of the Korean astronomical society = 천문학회지
  • 56, n.2
  • pp.195-199
  • 2023
  • 원문 바로보기
This paper is written as a follow-up observations to reinterpret the radial velocity (RV) of HD 36384, where the existence of planetary systems is known to be ambiguous. In giants, it is, in general, difficult to distinguish the signals of planetary companions from those of stellar activities. Thus, known exoplanetary giant hosts are relatively rare. We, for many years, have obtained RV data in evolved stars using the high-resolution, fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at the Bohyunsan Optical Astronomy Observatory (BOAO). Here, we report the results of RV variations in the M giant HD 36384. We have found two significant periods of 586 d and 490 d. Considering the orbital stability, it is impossible to have two planets at so close orbits. To determine the nature of the RV variability variations, we analyze the HIPPARCOS photometric data, some indicators of stellar activities, and line profiles. A significant period of 580 d was revealed in the HIPPARCOS photometry. H<sub>&#x03B1;</sub> EW variations also show a meaningful period of 582 d. Thus, the period of 586 d may be closely related to the rotational modulations and/or stellar pulsations. On the other hand, the other significant period of 490 d is interpreted as the result of the orbiting companion. Our orbital fit suggests that the companion was a planetary mass of 6.6 M<sub>J</sub> and is located at 1.3 AU from the host.