• 천문학회보
• /
• 제43권2호
• /
• pp.39.3-40
• /
• 2018

The presence of double red clump (RC) in the Milky Way bulge is widely accepted as evidence for a giant X-shaped structure originated from the bar instability. We suggested, however, a drastically different interpretation based on the multiple stellar populations phenomenon as is observed in globular clusters. Our discovery of a significant difference in CN-band between two RCs strengthens our scenario. On the other hand, recent Gaia survey provides trigonometric parallax distances for more than one billion stars in our Galaxy. These distance measurements would provide the important test as to the origin of the double RC in the Milky Way bulge. In this talk, we will present our preliminary results from Gaia DR2.

• 천문학회보
• /
• 제42권2호
• /
• pp.39.2-39.2
• /
• 2017

Over the last decade, deep studies of nearby galaxies have led to the discovery of vast stellar envelopes that are often rich in substructure. These components are naturally predicted in models of hierarchical galaxy assembly, and their observed properties place important constraints on the amount, nature, and history of satellite accretion. One of the most effective ways of mapping the peripheral regions of galaxies is through resolved star studies. Using wide-field cameras equipped to 8 m class telescopes, it has recently become possible to extend these studies to systems beyond the Local Group. Located at a distance of 3.6 Mpc, M81 is a prime target for wide-field mapping of its resolved stellar content. In this talk, we present the detailed results from our deep wide-field imaging survey of the M81 group with the Hyper Suprime-Cam (HSC), on the Subaru Telescope. We report on the analysis of the structures, stellar populations, and metallicities of old dwarf galaxies such as NGC3077, IKN, KDG061, as well as young stellar systems such as Arp's Loop and Holmberg IX. Several candidates for yet-undiscovered faint dwarf galaxies and young stellar clumps in the M81 group will also be introduced. The peculiar galaxy NGC3077 has been classified as the irregular galaxy. Okamoto et al. (2015, ApJ 809, L1) discovered an extended halo structure with S-shape elongated tails, obvious feature of tidal interaction. With a help of numerical simulation by Penarrubia et al. (2009, ApJ 698, 222), we will demonstrate that this tidal feature was formed during the latest close encounters between M81, M82, and NGC 3077, which induced star formation in tidally stripped gas far from the main bodies of galaxies. It is not clear whether the latest tidal interaction was the first close encounters of three galaxies. If NGC3077 is still surrounded by the dark matter halo, it implies that NGC3077 has undergone the first tidal stripping by larger companions. Kinematic studies of inter galactic globular clusters and planetary nebulae would tell us the past history of tidal interaction in this group of galaxies.

• 천문학회보
• /
• 제41권1호
• /
• pp.39.4-40
• /
• 2016

We aim to investigate formation of satellite sub-galactic structures around isolated dwarf galaxies using cosmological hydrodynamic zoom simulations. For this, we modify a cosmological hydrodynamic code, GADGET-3, in a way that includes gas cooling down to T~10K, gas heating by universal reionization when z < 8.9, UV shielding for high density regions of $n_{shield}$ > $0.014cm^{-3}$, star formation in the dense regions ($n_H$ > $100cm^{-3}$), and supernova feedback. To get good statistics, we perform three different simulations for different target galaxies of the same mass of ${\sim}10^{10}M_{sun}$. Each simulation starts in a cubic box of a side length of 1Mpc/h with 17 million particles from z = 49. The mass of dark matter (DM) and gas particle is $M_{DM}=4.1{\times}10^3M_{sun}$ and $M_{gas}=7.9{\times}10^2M_{sun}$, respectively, thus each satellite sub-galactic structure can be resolved with more than hundreds or thousands particles. We analyze total 90 sub-galactic structures that have formed outside of the main halos but infall the main halos. We found that 1) mini halos that interact more with the other mini halos tend to accrete the more mass, 2) mini halos that interact more before the reionization tend to form more stars, 3) mini halos with the more interaction tend to approach closer to the galactic center and have the lower orbital circularity, 4) survivals even in the strong tidal fields evolve baryon dominated system, such as globular clusters.

• 한국축산식품학회지
• /
• 제26권1호
• /
• pp.20-27
• /
• 2006

돈육을 이용한 수리미 유사물 제조시 첨가되는 NaCl 함량이 돈육 수리미의 젤 특성에 미치는 영향을 알아된 결과, NaCl의 첨가량이 증가함에 따라 젤 강도는 높아지지만, pH와 수분함량은 낮아지는 것으로 나타났다. 젤의 색깔은 첨가되는 NaCl의 함량이 $2{\sim}3%$일 때 선명하면서 밝은 것으로 나타났고, 4% 첨가되었을 때에는 황색토가 증가하여 색상이 어두워지는 것으로 나타났다. 젤의 미세구조를 관찰한 결과, NaCl의 첨가량이 증가함에 따라 염용성 단백질의 용해도가 증가하여 단백질 사이의 결합이 조밀하게 이루어지는 것으로 나타났으며, 이와 같은 이유로 인해 수분함량은 감소하지만 젤의 강도는 높아지는 것으로 나타났다. 관능평가에서 2% NaCl 첨가된 돈육 수리미의 색깔이 선명하면서 밝은 것으로 나타났고 전체적인 기호성도 우수한 것으로 평가되었다.