• Title/Summary/Keyword: bulge

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The Key role of the Bulge Compactness in Star-forming Activity in Late-type Galaxies

  • Jee, Woong-bae;Yoon, Suk-Jin
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.2
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    • pp.32.2-32.2
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    • 2015
  • Which mechanism governs star-formation activity in galaxies is still one of the most important, open questions in galactic astronomy. To address this issue, we investigate the specific star formation rate (sSFR) of late-type galaxies as functions of various structural parameters including the morphology, mass, radius, and mass compactness (MC). We use a sample of ~200,000 late-type galaxies with z = 0.02 ~ 0.2 from SDSS DR7 and a catalog of bulge-disk decomposition (Simard et al. 2011; Mendel et al. 2013). We find a remarkably strong correlation between bulge's MC and galaxy's sSFR, in the sense that galaxies with more compact bulge tend to be of lower sSFR. This seems counter-intuitive given that galactic sSFR is driven predominantly by disks rather than bulges and suggests that the central mass density plays a key role in recent star-forming activity. We discuss the physical cause of the new findings in terms of the bulge growth history and AGN activities.

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Numerical prediction of bursting failure in bulge forming using a seamed tube (심용접 튜브를 사용한 벌지 성형에서의 터짐불량 예측)

  • Kim, J.;Kim, Y.W;B.S. Kang
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.05a
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    • pp.240-243
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    • 2003
  • Finite element analyses for bursting failure prediction in bulge forming under combined internal pressure and independent axial feeding are carried out. By means of the FEM combined with Oyane's ductile fracture criterion based on Hills quadratic plastic potential, the forming limit and bursting pressure level are investigated for a seamed tube that comprises of weldment, heat affected zone(HAZ) and base material parts. Especially, in order to determine the material property of HAZ tensile tests for the base material and the weld metal are executed based on iso-strain approach. Finally, through a series of bulge forming simulations with consideration of the weldment and HAZ it is concluded that the proposed method would be able to predict the bursting pressure and fracture initiation site more realistically, so the approach can be extended to a wide range of practical bulge forming processes.

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Development of Bulge Testing System for Mechanical Properties Measurement of Thin Films : Elastic Modulus of Electrolytic Copper Film (박막의 기계적 물성 측정을 위한 벌지 시험 시스템 개발: 전해 동 박의 탄성 계수)

  • Kim, Dong-Iel;Huh, Yong-Hak;Kim, Dong-Jin;Kee, Chang-Doo
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.1807-1812
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    • 2007
  • A bulge testing system was developed to measure mechanical properties of thin film materials. A bulge pressure test system for pressurizing the bulge window of the film and a micro out-of-plane ESPI(Electronic Speckle Pattern Interferometric) system for measuring deflection of the film were included in the testing system developed. For the out-of-plane ESPI system, whole field speckle fringe pattern, corresponding to the out-of-plane deflection of the bulged film, was 3-dimensionally visualized using 4-bucket phase shifting algorithm and least square phase unwrapping algorithm. The bulge pressure for loading and unloading was controlled at a constant rate. From the pressure-deflection curve measured by this testing system, ain-plane stress-strain curve could be determined. In this study, elastic modulus of an electrolytic copper film 18 ${\mu}m$ was determined. The modulus was calculated from determining the plain-strain biaxial elastic modulus at the respective unloading slopes of the stress-strain curve and for the Poisson's ratio of 0.34.

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The study of moving and dissipation of floating mines due to wind forced river plume (바람영향하의 River plume에 따른 부유물체 확산 및 이동 연구)

  • Baek, Seong-Ho;Park, Kyeong-Ju
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2010.10a
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    • pp.295-298
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    • 2010
  • To find out moving and dissipation patterns of laid floating object estuary this paper has focused on forming, changing and variation of the wind forced river plume. In steady state(without external force), river can be form a bulge and downcoast alongshore current on gently sloped continental shelf. Under the downwelling wind and downcoast meanflow those river plume's patterns are similar with the steady state case except enhancement of downcoast transportation. Under the upwelling wind condition bulge linearly move to the northwest with 45 angle due to Ekman transport. It's moving speed are linear with the strength of the wind stress but moving paths are independent of that. So, in this case, floating object will be dissipate to outside as move to the upcoast.

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Assembling the bulge from globular clusters: Evidence from sodium bimodality

  • Lee, Young-Wook;Kim, Jenny J.;Chung, Chul;Jang, Sohee;Lim, Dongwook
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.37.2-37.2
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    • 2019
  • Recent investigations of the double red clump in the color-magnitude diagram of the Milky Way bulge cast serious doubts on the structure and formation origin of the outer bulge. Unlike previous interpretation based on an X-shaped bulge, stellar evolution models and CN-band observations have suggested that this feature is another manifestation of the multiple stellar population phenomenon observed in globular clusters (GCs). This new scenario requires a significant fraction of the outer bulge stars with chemical patterns uniquely observed in GCs. Here we show from homogeneous high-quality spectroscopic data that the red giant branch stars in the outer bulge ($>5.5^{\circ}$ from the Galactic center) are clearly divided into two groups according to Na abundance in the [Na/Fe] - [Fe/H] plane. The Na-rich stars are also enhanced in Al, while the differences in O and Mg are not observed between the two Na groups. The population ratio and the Na and Al differences between the two groups are also comparable with those observed in metal-rich GCs. Since these chemical patterns and characteristics are only explained by stars originated in GCs, this is compelling evidence that the outer bulge was mostly assembled from disrupted proto-GCs in the early history of the Milky Way. We will also discuss the implications of this result on the formation of the early-type galaxies in general.

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Effects of Forming Depth on the Deformation Behavior of Cup-like Tubes in Tube Spinning Process (튜브 스피닝 공정에서 성형깊이가 컵형 튜브의 변형거동에 미치는 영향)

  • Shin, Y.C.;Yoon, D.J.;Lim, S.J.;Choi, H.J.
    • Transactions of Materials Processing
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    • v.21 no.6
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    • pp.360-365
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    • 2012
  • The aim of this study was to investigate the effects of forming depth on the deformation behavior of cup-like tubes made of AISI1020 steel in tube spinning process. Spinning process was performed on cup-like tubes, which had an inner diameter of 34mm and thicknesses of 7, 8.5 or 11.5mm. The forming depths achieved were 3, 4, and 5.5mm. The complex deformation behaviors occurring during the tube spinning process was explained using the experimental results. Also analyzed were the causes of the material buildup and the bulge defect of inner surface, observed on cross section of tubes. The relationship between tube spinning conditions and the height of bulge defect was examined. The results indicate that bulge defect is increased with a decrease of the forming depth. Moreover, a critical forming depth exists for preventing the generation of the bulge defect in the tube spinning process. The present results will be useful for future decisions of forming depths for successful tube spinning of cup-like tubes.

SURFACE PHOTOMETRY OF NGC4419

  • CHOI JEONG TAE;ANN HONG BAE;LEE HYUNG MOK
    • Journal of The Korean Astronomical Society
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    • v.26 no.1
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    • pp.33-45
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    • 1993
  • We have conducted surface photometry of a spiral galaxy NGC4419, by making use of photographic plates in U, B, V and R-bands taken by 105cm Schmidt Camera at Kiso Observatory. Two dimensional surface brightness distributions as well as luminosity profiles along the major axis are examined in detail to decipher the morphological properties of the galaxy. Analysis of the color distributions of NGC4419 shows that B-V and U-B colors remain constant throughout the galaxy with a weak trend of blue bulge in B-V color. The blue bulge might indicate an active star formation in the nucleus of NGC4419. For a quantitative analysis of the luminosity distribution of NGC4419, the observed luminosity profiles are decomposed into bulge and disk components, assuming the bulge component to follow de Vaucouleurs $\gamma^{1/4}-law$ while the disk component is assumed to be exponential. The fitting generally fails at the central part and at the shoulder near r = 15' where bulge and disk components overlap. The failure at the central part cannot be attributed wholly by the seeing disk since the core-radius of the central plateau is much larger than the width of point spread function. The failure at shoulder could be due to the luminosities from the spiral arms.

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An exact solution for mechanical behavior of BFRP Nano-thin films embedded in NEMS

  • Altabey, Wael A.
    • Advances in nano research
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    • v.5 no.4
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    • pp.337-357
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    • 2017
  • Knowledge of thin films mechanical properties is strongly associated to the reliability and the performances of Nano Electro Mechanical Systems (NEMS). In the literature, there are several methods for micro materials characterization. Bulge test is an established nondestructive technique for studying the mechanical properties of thin films. This study improve the performances of NEMS by investigating the mechanical behavior of Nano rectangular thin film (NRTF) made of new material embedded in Nano Electro Mechanical Systems (NEMS) by developing the bulge test technique. The NRTF built from adhesively-bonded layers of basalt fiber reinforced polymer (BFRP) laminate composite materials in Nano size at room temperature and were used for plane-strain bulging. The NRTF is first pre-stressed to ensure that is no initial deflection before applied the loads on NRTF and then clamped between two plates. A differential pressure is applying to a deformation of the laminated composite NRTF. This makes the plane-strain bulge test idea for studying the mechanical behavior of laminated composite NRTF in both the elastic and plastic regimes. An exact solution of governing equations for symmetric cross-ply BFRP laminated composite NRTF was established with taking in-to account the effect of the residual strength from pre-stressed loading. The stress-strain relationship of the BFRP laminated composite NRTF was determined by hydraulic bulging test. The NRTF thickness gradation in different points of hemisphere formed in bulge test was analysed.

Relation between Black Hole Mass and Bulge in Hard X-ray selected Type 1 AGNs

  • Son, Suyeon;Kim, Minjin;Barth, Aaron J.;Ho, Luis C.
    • The Bulletin of The Korean Astronomical Society
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    • v.45 no.1
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    • pp.62.1-62.1
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    • 2020
  • We present a scaling relation between black hole (BH) mass and bulge luminosity for 35 nearby (z<0.1) type 1 active galaxies, selected from the 70-month Swift-BAT X-ray source catalog. Thanks to the unbiased selection and proximity of the parent sample, our sample is suitable to study the physical connection between central black holes and host galaxies. We use the F814W images obtained with the Advanced Camera for Surveys on Hubble Space Telescope, to perform the imaging decomposition with GALFIT. With a careful treatment on the PSF model, we measure the I-band bulge brightness robustly. In combination with the BH mass estimated from a single-epoch spectroscopic data, we present the correlation between BH mass and bulge luminosity of the target AGNs. We demonstrate that our sample marginally lies off from the M(BH)-L(bulge) relation of inactive galaxies. We discuss possible physical origins of this discrepancy. Finally, we present how the relation depends on the photometric properties of AGNs and host galaxies, which may provide an useful insight on the co-evolution between BHs and host galaxies.

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Investigating the cosmic evolution of the black hole mass-bulge luminosity scaling relation

  • Park, Daeseong;Woo, Jong-Hak;Treu, Tommaso;Bennert, Vardha N.;Malkan, Matthew A.;Auger, Matthew W.
    • The Bulletin of The Korean Astronomical Society
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    • v.38 no.2
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    • pp.42.2-42.2
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    • 2013
  • We investigate the cosmic evolution of the black hole mass-bulge luminosity relation with a sample of 52 moderate-luminosity AGNs at $z{\simeq}0.36$ and $z{\simeq}0.57$, corresponding to look-back times of 4 and 6 Gyrs. By employing robust multi-component spectral and structural decomposition methods to the obtained high-quality Keck spectra and high-resolution HST images, black hole masses ($M_{BH}$) are estimated from the Hbeta broad emission line with the 5100A nuclear luminosity, and bulge luminosities ($L_{bul}$) are derived from the surface photometry. Based on these consistent measurements, we constrain the redshift evolution of the $M_{BH}-L_{bul}$ relation by performing the Monte Carlo simulations designed to account for selection effects. We provide implications of our results in terms of the black hole-galaxy co-evolution and discuss possible bulge growth mechanisms.

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