• Title/Summary/Keyword: metallicity

Search Result 221, Processing Time 0.021 seconds

Tracing Metallicity in the Scenario of High Velocity Clouds (HVCs) Colliding with our Milky Way

  • Sung, Kwang Hyun;Kwak, Kyujin
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.39 no.2
    • /
    • pp.77.2-77.2
    • /
    • 2014
  • Questions of how our Milky Way evolves through the interaction with its environment have been constantly raised. One particularly interesting question is how the metallicity would change as our Milky Way goes through collision with HVCs. Because of the possibility of HVCs providing fuel for star formation in the Galactic disk, we simulate the collision between HVCs and the Galactic disk. More specifically, we trace how the Galactic metallicity changes throughout the process of HVCs colliding with our Milky Way based upon a specific scenario that HVCs are primordial gas left-overs from an ancient galaxy formation. Such mixing between metal-rich gas (disk) and metal-poor HVC can be traced by running numerical simulations with the FLASH code due to its capability of tracking down the abundance change of a specific element such as carbon at each time step of the hydrodynamic evolution. As for now, we give how this mixing depends on model parameters that we choose such as collision speed, initial metallicities, temperature and so on.

  • PDF

GALAXIES AND DUST AT HIGH REDSHIFT

  • HUNSTEAD RICHARD W.;PETTINI MAX;KING DAVID;SMITH LINDA J.
    • Journal of The Korean Astronomical Society
    • /
    • v.29 no.spc1
    • /
    • pp.35-38
    • /
    • 1996
  • Much of our knowledge about the formation and evolution of high-redshift galaxies has come from studying the absorption signatures they impress on the spectra of background QSOs. The damped Lyman $\alpha$ (DLA) systems, in particular, have proved to be valuable probes of the metallicity and dust at redshifts z $\~$2-3 in what are the likely progenitors of galaxies like our own. At z $\~$ 2 we find that the typical metallicity of the universe was 1/15 solar. In addition, we find clear evidence for the existence of trace amounts of interstellar dust in DLA galaxies and show that this is consistent with recent high resolution spectra of DLAs with the Keck telescope, despite claims to the contrary.

  • PDF

Near-Infrared Color-Metallicity Relation for Globular Cluster System in Elliptical Galaxy NGC 4649

  • Jeong, Jong-Hoon;Kim, Sooyoung;Yoon, Suk-Jin
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.42 no.2
    • /
    • pp.76.2-76.2
    • /
    • 2017
  • We present Subaru Near-Infrared (NIR) photometry for globular clusters (GCs) in the giant elliptical galaxy NGC 4649 (M60) belonging to the Virgo cluster. NIR data are obtained in Ks-band with the Subaru/MOIRCS, and matching HST/ACS optical data available in literature are used to explore the origin of GC color bimodality. A clear bimodal color distribution is observed in the optical color (g-z), in which the ratio between blue and red GCs is 4:6. By contrast, the more metallicity-sensitive optical-NIR colors (g-Ks, z-Ks) show a considerably weakened bimodality in their distributions. The color-color relation of the optical and NIR colors for the GC system shows a nonlinear feature, supporting that the optical color bimodality observed in NGC 4649 GC system is caused by nonlinear color-metallicity relations (CMRs).

  • PDF

THE CHEMICAL EVOLUTION OF THE SOLAR NEIGHBORHOOD: AGE-METALLICITY RELATION OF F-STARS

  • Ann, Hong-Bae;Kang, Yong-Hee
    • Journal of The Korean Astronomical Society
    • /
    • v.18 no.2
    • /
    • pp.79-85
    • /
    • 1985
  • From the uvby, $H_{\beta}$ photometry of intermediate population II F-stars in the catalogue of Olsen (1983), we derived age-metallicity relations for these stars, using Hejlesen's (1980) isochrone. The derived age-metallicity relations well coincide with the theoretical predictions by the unclosed two-zone model of Lee and Ann (1981). There are few extremely metal poor F-stars in the vicinity of the Sun, and it is very likely that the initial rapid metal enrichment in the galactic disk might have been processed through the fast collapse of the disk at the very early epoch.

  • PDF

Metallicity, age, and alpha-element of the globular clusters in the Virgo giant elliptical galaxy NGC 4636

  • Park, Hong-Soo;Lee, Myung-Gyoon;Hwang, Ho-Seong;Arimoto, Nobuo;Yamada, Yoshihiko;Tamura, Naoyuki;Onodera, Masato
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.35 no.2
    • /
    • pp.31.1-31.1
    • /
    • 2010
  • We present a spectroscopic study of the globular clusters (GCs) in the giant elliptical galaxy (gE) NGC 4636 in the Virgo cluster. Line indices of GCs in NGC 4636 are measured from the integrated spectra obtained with Faint Object Camera and Spectrograph (FOCAS) on the Subaru Telescope. We derive the [Fe/H] of the GCs in NGC 4636 using Brodie & Huchra (1990) method. The [Z/H], age, and alpha-element of the GCs are obtained from the comparison of the Lick line indices with the SSP model grid. We investigate the distribution and radial variation of the metallicity, age, and alpha-element of NGC 4636 GCs. The metallicity distribution of NGC 4636 GCs shows a bimodality. The chemical properties of these GCs show little radial variation. These results will be discussed with regard to the formation and evolution of NGC 4636.

  • PDF

METALLICITY OF GLOBULAR CLUSTER M13 FROM VI CCD PHOTOMETRY

  • Sohn, Young-Jong
    • Journal of Astronomy and Space Sciences
    • /
    • v.17 no.2
    • /
    • pp.133-140
    • /
    • 2000
  • From the VI images of M13, obtained by using 2K CCD camera and the BOAO 1.8m telescope, we derive the(V - I) - V CMD of M13. From the shapes of red giant branch, the magnitude of horizontal branch, and the giant branch bump on the constructed CMD, we determined the metallicity of the globular cluster to be 1.74${\lesssim}$[Fe/H]${\lesssim}$-1.41. The good agreement between our determination of [Fe/H] and those determined by using other methods implies that the morphology of red giant and horizontal branches on (V - I) - V CMD's can be good indirect metallicity indicators of Galactic globular clusters.

  • PDF

Ten Years of Debate on the Origin of Globular Cluster Color Bimodality

  • Kim, Hak-Sub;Yoon, Suk-Jin
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.41 no.1
    • /
    • pp.32.2-32.2
    • /
    • 2016
  • The globular cluster (GC) systems in most elliptical galaxies show bimodal color distributions. This phenomenon has been generally regarded as a bimodal metallicity distribution, indicating the presence of two sub-populations in a GC system. However, since a new explanation on the bimodality was introduced where the nonlinear metallicity-to-color conversion can cause bimodal color distributions, the origin of this phenomenon has been under hot debate. In this presentation, we briefly review the ten-year debate on the origin of GC color bimodality, and present our recent pieces of evidence on the nonlinear nature of GC color-metallicity relations.

  • PDF

Metallicity Gradients of CALIFA Shell Galaxies

  • Lee, Hye-Ran;Lee, Joon Hyeop;Pak, Mina;Park, Byeong-Gon
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.44 no.1
    • /
    • pp.76.2-76.2
    • /
    • 2019
  • Shells in early-type galaxies are low surface brightness tidal debris, which are wide concentric arcs of overdense stellar regions with large opening angles. The most widely accepted mechanism today for shell formation is the merger scenario, but the dominant merger type producing shells is not clearly understood yet: major/minor and wet/dry mergers. Since shells are regarded as smoking-gun evidence of merging events, detailed understanding of shell galaxies is very useful to constrain the formation process of early-type galaxies. In this study, we investigate the metallicity gradients of eight early-type shell galaxies using CALIFA IFU data to better understand the nature and origins of galaxy shells. We estimate simple stellar population properties out to three effective radius from the measurement of Lick/IDS absorption line indices. We compare the metallicity gradients of shell galaxies with those of normal early-type galaxies in the same mass range. In this presentation, we discuss how much the gradients of shell galaxies are different from those of normal early-type galaxies and what the existence of galaxy shells implies about galaxy formation.

  • PDF

Magnetism and Half-metallicity of Co2TiSn(001) Surfaces: A First-principles Study (Co2TiSn(001) 표면의 자성 및 반쪽금속성에 대한 제일원리연구)

  • Jin, Y.J.;Lee, J.I.
    • Journal of the Korean Magnetics Society
    • /
    • v.18 no.4
    • /
    • pp.131-135
    • /
    • 2008
  • The electronic structures, magnetism, and half-metallicity of the full-Heusler $Co_2TiSn$(001) surfaces have been investigated by using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. We have considered both of the Co atoms terminated(Co-term) and the TiSn atoms terminated(TiSn-term) surfaces. From the calculated density of states, we found that the half-metallicity was destroyed at the surface of the Co-term, while the half-metallicity was retained at the TiSn-term. For the surface of the Co-term, due to the reduced coordination number the occupied minority d-states were shifted to high energy regions and that cross the Fermi level, thus destroy the surface half-metallicity. On the other hand the surface states at the surface of the TiSn-term were located just below the Fermi level, which reduces the minority spin-gap with respect to that of the center layer. The calculated magnetic moment of the surface Co atom for the Co-term was increased by 10 % to 1.16 ${\mu}_B$ with respect to that of the inner-layers, while the magnetic moment of the subsurface Co atom in the TiSn-term has almost same value of the innerlayers(1.03 ${\mu}_B$).

JK PHOTOMETRY OF BRIGHT GIANTS IN NGC6712

  • KYEONG JAE-MANN;BYUN YONG-IK
    • Journal of The Korean Astronomical Society
    • /
    • v.31 no.2
    • /
    • pp.127-140
    • /
    • 1998
  • With a large format near-infrared camera at the 2.2-m telescope on Mauna Kea Observatory, we performed J K near-infrared observations for the metal rich globular cluster NGC6712. This cluster lies near the galactic plane and therefore suffers heavy reddening. We present the near-infrared color-magnitude diagram and also derive the metallicity ([Fe/H] ${\~}-0.96{\pm}0.27$) as well as its distance modulus ((m - M) ${\~}13.42{\pm}0.12$).

  • PDF