• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.60.1-60.1
• /
• 2011

We present preliminary results of a statistical study on star formation history of infrared luminous galaxies selected from a IRAS-SDSS matched sample. We derive their star formation histories by comparing observed optical spectra and stellar population synthetic model templates. We find that young population fraction (<500 Myr) increases with infrared luminosity, while AGN-host (based on optical line ratios) galaxies show an enhancement of star formation at intermediate age (around 1 Gyr) compared with starburst galaxies. These results support that infrared luminosity is dominated by starburst activity and that there is an evolutionary connection from starburst to AGN.

• The Bulletin of The Korean Astronomical Society
• /
• v.45 no.1
• /
• pp.49.1-49.1
• /
• 2020

In this talk, I will discuss a few different techniques to reconstruct different cosmological functions, such as the primordial power spectrum and the expansion history. These model independent techniques are useful because they can discover surprising results in a way that nested modeling cannot. For instance, we can use the modified Richardson Lucy algorithm to reconstruct a novel primordial power spectra from the Planck data that can resolve the "Hubble tension". This novel primordial power spectrum has regular oscillatory features that would be difficult to find using parametric methods. Further, we can use Gaussian process regression to reconstruct the expansion history of the Universe from low-redshift distance datasets. We can also this technique to test if these datasets are consistent with one another, which essentially allows for this technique to serve as a systematics finder.

• Publications of The Korean Astronomical Society
• /
• v.37 no.3
• /
• pp.49-57
• /
• 2022

In this study, we collected articles published in the Publication of the Korean Astronomical Society (PKAS) from 1984 to 2021, and performed quantitative analyses of their various aspects. PKAS is the journal where authors can publish research papers in Korean as well as English. It seems to have an advantage of the better accessibility to all people than other astronomy journals in English only. From 1984 to 2000, the number of articles published in PKAS has been steadily increased. From 2000, the number of published articles showed a tendency to decrease slightly every year. After 2010, the number of articles in PKAS has shown a sharp decline until now. Interestingly, in this period it is found that the topics published articles became various, in particular, many articles concerning historical astronomy began to be published. PKAS was selected as an accredited journal in 2018. This is a very positive situation, and we think the future direction of PKAS is encouraging. Considering these circumstances, the PKAS is suggested to reflect ideas of "interdisciplinary fusion" and "diversity" in publishing articles in the journal for its promising future.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.1
• /
• pp.84.1-84.1
• /
• 2014

We report the spatial distribution of early-type stars and pre-main-sequence (PMS) stars around the starburst type young open cluster Westerlund 2. The early-type were selected from UBVI photometric data, while the PMS members were identified from their X-ray emission and mid-infrared excess. The northern clump of the cluster is composed mainly of PMS stars detected in both optical and X-ray and seems to be coeval to the cluster, while PMS stars in the bright bridge region are highly obscured in optical wavelength. The bright bridge appear to be an on-going star forming region possibly triggered by the strong radiation field from both sides-massive stars in Westerlund 2 and WR 20b. We also found that there are many early-type stars not only in the cluster but also farther from the cluster up to several times of the cluster radius. These early-type stars are well aligned from east to southwest of the cluster. We conclude these early-type stars are members of an OB association in the RCW 49 nebula. This report indicates there is a complex star formation history in Westerlund 2 and its surrounding H II region, the RCW 49 nebula.

• Publications of The Korean Astronomical Society
• /
• v.26 no.3
• /
• pp.89-101
• /
• 2011

The International Olympiad on Astronomy and Astrophysics (IOAA) initiated by the Thailand Astronomical Society in 2007 is an annual competition for high school students. One of its aim is to enhance the development of international exchange in the field of school education in astronomy and astrophysics. This paper first provides the overview of the IOAA in terms of key regulations based on its statutes, history and current status. Secondly, the published syllabus of the IOAA is used for content analysis according to subject areas regarding the exam questions of the IOAA in theoretical, observational and data analysis parts from 2007 to 2010. Also, a scientific inquiry framework is applied to the same questions for assessment based on scientific inquiry in the cognitive aspect with two sub-classes of scientific knowledge and scientific reasoning. Among a dozen astronomy subject areas listed on the syllabus, the theoretical part of the IOAA makes more frequent use of the Sun, the solar system, properties of stars, and concept of time. In content knowledge, a factor of scientific knowledge, the IOAA questions, especially in the theoretical part have a lesser degree in difficulty than the IAO (International Astronomy Olympiad) exam questions for the same period whose degree in difficulty is comparable to college level. With regard to scientific reasoning, the IOAA questions tend to involve convergent rather than divergent thinking. Lastly, in light of these findings, discussions are given on the outcome of Korean participation in the previous IOAAs and ways to help better in preparing Korean students for future astronomy Olympiads.

• The Bulletin of The Korean Astronomical Society
• /
• v.27 no.2
• /
• pp.28-28
• /
• 2002

• Publications of The Korean Astronomical Society
• /
• v.31 no.3
• /
• pp.57-63
• /
• 2016

We summarize our preliminary study on the research cooperation method in the astronomy field between Republic of Korea (South Korea) and Democratic People's Republic of Korea (North Korea). To investigate the recent astronomical activities of North Korea, we have surveyed the published records of research papers and international collaborations associated with North Korean astronomers. We found only 4 astronomical papers among the identified 260 SCI papers related to North Korean researchers for the past 11 years. North Korean astronomers had very few interactions with the international astronomical society before rejoining IAU in 2012. Recently, North Korea made several astronomical research exchanges with China and Netherlands. They seemed to attend several international conferences and present their research results. We have studied possibilities to establish international networks to encourage the cooperation between South and North, and suggest to start collaboration in the historical astronomy. The collaboration can be expanded gradually to other fields in astronomy. There are many obvious political difficulties to have interactions with North Koreans. However, it will be necessary to make a long-term plan considering the reunification.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.2
• /
• pp.42.2-42.2
• /
• 2014

We investigate the history of formation of ~400 galaxies in four Abell clusters at 0.04

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.232.1-232.1
• /
• 2012

With flourishing of new facilities, we are now set to expand the horizon of the human knowledge of the universe deep into the very beginning of the cosmic history of astronomical objects. In such an endeavor, extreme objects and cosmic events such as violent cosmic explosions, rapidly growing supermassive black holes, and proto-clusters of galaxies, are the objects to be investigated in order to unveil what was happening in the very early universe. We will discuss what we have learned and are expecting to discover from such extreme objects about the infant universe both currently and in future, highlighting some of our recent works.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.2
• /
• pp.39.1-39.1
• /
• 2021

In this presentation, study of the energetic astronomical phenomena, active galactic nucleus (AGN) and gravitational wave (GW) source, with time-series observation will be reported. They emit large amounts of energy and play an important role in the history of the Universe. First, intra-night variability of AGNs is studied using Korea Microlensing Telescope Network (KMTNet). Second topic is photometric reverberation mapping which is applied for 11 AGNs with medium-bands and Lee Sang Gak Telescope. Last, three gravitational wave events were followed-up by various optical telescopes. Each topic will be specifically addressed in the presentation.