• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.88.1-88.1
• /
• 2012

We utilize Sloan Digital Sky Survey DR7 spectroscopic data of ~340 star forming galaxies in the Virgo cluster to investigate their chemical properties depending on the environments. The chemical evolution of galaxies is linked to their star formation histories (SFHs), as well as to the gas interchange in different environments. In this sense, galaxy metallicity could be an observable parameter providing information on the impact of the environment on the galaxy SFH and/or the galaxy gas content. Thus, we derived gaseous metallicity (e.g., oxygen abundance) of star forming galaxies located in different regions of the Virgo cluster using well-known empirical calibrations. We also estimated their star formation rate (SFR) using H alpha luminosity. Inorder to investigate the chemical properties of these galaxies, we examined relations between various parameters: metallicity vs. luminosity, SFR vs. luminosity, and metallicity vs. cluster-centric radius. From our results, we discuss environmental effects of cluster to the chemical properties of star forming galaxies.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.2
• /
• pp.87.1-87.1
• /
• 2017

We present preliminary results of elemental abundances of six ultra-metal poor (UMP; [Fe/H] < -4.0) stars derived from high-resolution spectra obtained by Gemini/GRACES. The UMP candidates were selected for the high-resolution follow-up from the low-resolution spectra of Sloan Digital Sky Survey (SDSS). We investigate possible progenitors of the UMP objects by comparing the measured abundance patterns with yields that various supernova models predict. Our results can provide stringent constraints on the mass range of the first generation of stars, which are the progenitors of the UMP objects.

• Journal of Microbiology and Biotechnology
• /
• v.27 no.2
• /
• pp.412-415
• /
• 2017

Prebiotics improve the growth or activities of specific microbial genera and species in the gut microbiota in order to confer health benefits to the host. In this study, we investigated the effect of poly-gamma-glutamate (${\gamma}-PGA$) as a prebiotic on the gut microbiota of mice and the organ distributions of ${\gamma}-PGA$ in mice. Pyrosequencing analysis for 16S rRNA genes of bacteria indicated that oral administration of ${\gamma}-PGA$ increased the abundance of Lactobacillales while reducing the abundance of Clostridiales in murine guts. It is suggested that oral administration of ${\gamma}-PGA$ can be helpful for modulating the gut microbiota as a prebiotic.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.77.3-77.3
• /
• 2016

In our previous study, we showed that the peculiar globular cluster M22 contains two distinct stellar populations with different physical properties, having different chemical compositions, spatial distributions and kinematics. We proposed that M22 is most likely formed via a merger of two GCs with heterogeneous metallicities in a dwarf galaxy environment and accreted later to our Galaxy. In their recent study, Mucciarelli et al. claimed that M22 is a normal mono-metallic globular cluster without any perceptible metallicity spread among the two groups of stars, which challenges our results and those of others. We devise new strategies for the local thermodynamic equilibrium abundance analysis of red giant branch stars in globuar clusters and show there exists a spread in the iron abundance distribution in M22.

• Publications of The Korean Astronomical Society
• /
• v.30 no.2
• /
• pp.159-161
• /
• 2015

We have carried out optical spectroscopic measurements of emission lines for a sample of Galactic planetary nebulae with Wolf-Rayet (WR) stars and weak emission-line stars (wels). The plasma diagnostics and elemental abundance analysis have been done using both collisionally excited lines (CELs) and optical recombination lines (ORLs). It was found that the abundance discrepancy factors ($ADF{\equiv}ORL/CEL$) are closely correlated with the difference between temperatures derived from forbidden lines and those from $He\;{\small{I}}$ recombination lines, implying the existence of H-deficient materials embedded in the nebula. The $H{\beta}$ surface brightness correlations suggest that they might be also related to the nebular evolution.

• Bulletin of the Korean Space Science Society
• /
• 2010.04a
• /
• pp.35.1-35.1
• /
• 2010

Using the spectroscopic analysis and the theoretical modeling, physical properties of the nearby astrometric binary $\mu$ Cas have been determined. In spite of the well-defined parallax and astrometric orbit, there has been a chronic mass ratio problem between components. Recently, the radius of the primary component has been detected from the optical interferometric observation of the CHARA array. Using the high resolution spectroscopic analysis, we found that $\mu$ Cas have $\alpha$-enhanced chemical composition with respect to the scaled solar abundance by a factor of two. Combining our abundance analysis with recently determined physical properties, the consistent models for $\mu$ Cas have been constructed within the frame work of standard stellar theory. Through a statistical minimization between theoretical model grids, a reliable set of physical dimensions has been defined. Furthermore, the mode oscillation frequency of the best model has been calculated.

• Journal of The Korean Astronomical Society
• /
• v.52 no.3
• /
• pp.83-88
• /
• 2019

Using ALMA observations of the $^{13}CN$ and DCN lines in the massive star-forming region G33.92+0.11A, we investigate the CN/HCN abundance ratio, which serves as a tracer of photodissociation chemistry, over the whole observed region. Even considering the uncertainties in calculating the abundance ratio, we find high ratios (${\gg}1$) in large parts of the source, especially in the outer regions of star-forming clumps A1, A2, and A5. Regions with high CN/HCN ratios coincide with the inflows of accreted gas suggested by Liu et al. (2015). We conclude that we found strong evidence for interaction between the dense gas clumps and the accreted ambient gas which may have sequentially triggered the star formation in these clumps.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.46.2-46.2
• /
• 2013

We utilize Sloan Digital Sky Survey DR7 spectroscopic data of ~380 star forming galaxies in the Virgo cluster to investigate their chemical properties depending on the environments. The chemical evolution of galaxies is linked to their star formation histories as well as to the gas interchange in different environments. We derived star formation rate (SFR) and gaseous metallicity (e.g., oxygen abundance) of star forming galaxies. Combining with GALEX ultraviolet photometry and ALFALFA HI 21 cm data, we examine the relations between SFRs, metallicity, and HI deficiency of galaxies in various regions of the Virgo cluster. We also quantify the degree of ram pressure around galaxy using the ROSAT X-ray surface brightness map. We discuss environmental effects on the chemical properties and evolution of star forming galaxies.

• Journal of The Korean Astronomical Society
• /
• v.33 no.2
• /
• pp.97-110
• /
• 2000

Planetary nebulae provide a direct way to probe elemental abundances, their distributions and their gradients in populations in nearby galaxies. We investigate bulge planetary nebulae in M 31 and M 32 using the strong emission lines, H$\alpha$, He I, [O III], [N II], [S II] and [Ne III]. From the [O III] 4363/5007 line ratio and the [O II] 3727/3729, we determine the electron temperatures and number densities. With a standard modeling procedure (Hyung, 1994), we fit the line intensities and diagnostic temperatures, and as a result, we derive the chemical abundances of individual planetary nebulae in M 31 and M 32. The derived chemical abundances are compared with those of the well-known Galactic planetary nebulae or the Sun. The chemical abundances of M 32 appear to be less enhanced compared to the Galaxy or M 31.

• Korean Journal of Environmental Agriculture
• /
• v.35 no.1
• /
• pp.39-45
• /
• 2016

BACKGROUND: This study aimed to evaluate the combined effects of three components (NPK) of chemical fertilizers with basal application of compost on soil organisms.METHODS AND RESULTS: The soil was treated with five treatments continuously for 15 years: control, PK, NK, NP and NPK. The application of N increased plant growth or biomass, and enhanced organic matter content in the soils. Levels of microbial phospholipid fatty acids (PLFAs) in the soils did not show marked differences among the soils treated with different treatments. However, the principal component analysis showed the changes in the structure of the microbial community in the soil, depending on treatments added. Nitrogen application caused a decrease of pH and an increase of EC in the soils, and these environmental stresses appeared to offset the promoting effect of increased organic matter content on microbial abundance. The abundance of bacterivorous nematodes was the highest in the soils after treating NPK; however, the abundance of fungivorous nematodes was unaffected. There was no significant correlation between the abundances of microbial groups and their feeders. Organic matter content was significantly correlated with the abundance of nematodes in the soils.CONCLUSION: Our results showed that chemical fertilizers affect the soil food chains through both biotic and abiotic factors, and a trophic cascade in the soils may not occur in response to long-term fertilization.