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Models of chemical enrichment

Models of chemical enrichment. Appears like the Dawn Fair as the Moon Bright as the Sun Majestic as the Stars by Nari Jeong 2007. 4. 9. 연령 , 금속 함량과 운동 상태에 의하여 은하계 내의 종족들을 구분 -> 금속 함량과 연령과의 관계가 중요 별의 금속 함량 : 별이 생겨난 모체인 기체에서 중금속의 농도화 ( enrichment ) 의 정도를 표시하는 것

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Models of chemical enrichment

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  1. Models of chemical enrichment Appears like the Dawn Fair as the Moon Bright as the Sun Majestic as the Stars by Nari Jeong 2007. 4. 9

  2. 연령, 금속 함량과 운동 상태에 의하여 은하계 내의 종족들을 구분 -> 금속 함량과 연령과의 관계가 중요 • 별의 금속 함량: 별이 생겨난 모체인 기체에서 중금속의 농도화(enrichment) 의 정도를 표시하는 것 • 금속 함량이 풍부하다는 것은 상대적인 표현!! • 왜 중요한가? -> 은하 진화 과정에서는 화학과 역학이 서로 연결 되어 있기 때문 <관측> : 금속 함량비가 낮을수록 -> 은하원반으로부터 높은 곳 위치 • 성간 매질의 재순환(recycling) 기본 개념에 의해 생각!! < help thinking ^-^> 1. 성간 매질의 구름에서 별들 탄생 = 모체인 기체 함량 비 반영 2. 궤도 운동도 역시!! 3. 은하가 늙어 감에 따라 중 원소 함량 비 증가

  3. Model of chemical enrichment • Interpretation of both observations of external galaxies and of stars within the Milky Way • First model : completely isolated system • Second model : vents metal rich gas • Third model : accretes metal-free gas from its surroundings <References> • Pagel, B.E.J., 1997. Nucleosynthesis and Chemical Evolution of Galaxies (Cambridge: Cambridge University Press) • Talbot, R.J & Arnett, W.D. 1971, ApJ 170, 409. Closed-box model

  4. The closed-box model • Talbot & Arnett(1971) : chemical evolution of a portion of a galaxy such as the solar neighborhood. • Focuses on -> a narrow annulus of galactocentric radius <8.2.6 : Metallicities of disk galaxies p516 > The metallicities of the ISM of a disk galaxy -> strenghths of emission lines in the spectra of HII regions. -> depends systematically on : galactocentric radius • Assumes -> no material either enter or leaves this region. Turbulent motions -> keep the gas well stirred -> homogeneous Gas gradually consumed -> remain : heavy elements. • Metallicity Interstellar gas Z = Mh/Mg • Total mass -> forming a mass of new stars • instantaneous recycling approximation

  5. The leaky-box model • Milky Way stars form in molecular cloud complexes ->no means closed boxes molecular -> small fraction -> turned into stars Supernovae!! -> out of the cloud : formation of globular cluster elliptical galaxies • Hartwick(1976) leaky-box model -> Milky Way’s halo p688 F10.39 • Line-strengths of elliptical galaxies : central velocity dispersions • Leaky-box model -> gas was exhausted. <Figure 5.18> • Contain both cool and hot parcels of gas -> ISM will consist of two phases one hot & one cold. • One-dimensional velocity dispersion -> corresponds temperature T

  6. Hot component of the ISM : 200kms^-1 Dwarf : 10kms^-1 - little self-enrichment Giant elliptical : >200kms^-1 - self-enrichment • Gravitational potential -> gas is lifted f : a number of order a few Esn : energy injected into the ISM per unit mass converted into stars C : increse from a value smaller than unity for giant elliptical galaxies to one of order a few for dwarf ellipticals • -> Supernovae : lift gas from the galaxies • Unfortunately!! -> uncertain Why? Dark halos

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