銀河物理学特論 I G l ti Astrophysics Galactic A t h i I I-3: Stellar p population p / Star formation of galaxies 2015/04/27 Galaxy morphology and typical spectra 銀河の形態と典型的 銀河の形態と典型的スペクトル クトル Strateva et al. 2001, AJ, 122, 1861 Spectral models of galaxies : stellar population synthesis 銀河の 銀河のスペクトルモデル：星種族合成 クトル デル 星種族合成 • Stellar spectra for various types, luminosities, and metallicity (chemical composition) Bruzual & Charlot 2003, MNRAS, 344, 1000 • Stellar evolution model, isochrone model • Libraries: Padova 1994, Padova 2000, Geneva etc… Initial Mass Function (IMF) • Salpeter p IMF with simple p power-law p • Kroupa IMF, Chabrier IMF with low-mass cut-off • • • Star Formation History y : Star formation rate as a function of age g Chemical enrichment Dust extinction • Spectral types of stars 星の 星のスペクトルタイプ クトルタイプ • O-type (50,000-28,000K), B-type (28,000-10,000K), A-type (10,000-7,500K), F-type (7,500-6,000K), G-type (6,000-5,000K), K-type (5,000-3,500K), M-type (3 500-2 500K) main sequence stars (3,500-2,500K) From https://www.cfa.harvard.edu/ pberlind/atlas/atframes.html Stellar evolution model 星の進化 デル 星の進化モデル Red numbers indicate time scale for each period in logarithmic scale (yr): 6 means 10^6 years. Iben QJRAS (1985, 26, 1) Single stellar population 一種類の星種族 種類の星種族 Maraston 2005, MNRAS, 362, 799 Isochrones 1 等時曲線 1 AGB, Thermal-Pulses AGB AGB, Thermal-Pulses AGB Main-sequence turn off Charlot et al. 1996, ApJ, 457. 625 Model isochrones 等時曲線の デル 等時曲線のモデル • Model isochrones compared with color-magnitude diagrams of Hyades and M67 (galactic open clusters = young stellar population). Bruzual & Charlot 2003, MNRAS, 344, 1000 Initial Mass Function 初期質量関数 • Salpeter IMF: power-law with slope of 1.35 • The slow of the IMF is relatively constant among clusters in the MW galaxy, but in the lower mass range there is a large scatter among various regions. Bastian et al. 2010, arXiv:1001.2965 IMF of MW disk 銀河系ディ クの初期質量関数 銀河系ディスクの初期質量関数 Chabrier 2004, astro-ph/0409465 Chabrier 2003 2003, PASP PASP, 115 115, 763 Spectra of single stellar population model 一種類の星種族のスペクトルモデル 種類の星種族の クトル デル • Synthesised spectra: Single Stellar Population (SSP ) models Bruzual & Charlot 2003, MNRAS, 344, 1000 Contribution from each evolutionally phase それぞれの進化フ それぞれの進化フェーズの寄与 ズの寄与 Charlot et al. 1996, ApJ, 457. 625 55: Main-sequence turn off, 100: RGB-tip, 120: early-AGB, 140: Thermal-Pulse AGB Contribution from each evolutionally phase それぞれの進化フ それぞれの進化フェーズの寄与 ズの寄与 Maraston 2005, MNRAS, 362, 799 Observables of stellar systems 星の系の観測量 Difference in metallicity: Difference in evolutionary track: Cause different color in entire age rage. Cause different color for young populations Bruzual & Charlot 2003, MNRAS, 344, 1000 Observables of stellar systems 星の系の観測量 Difference in stellar spectra : Difference in IMF: No significant effect. Cause difference in Mass-to-Light ratio Bruzual & Charlot 2003, MNRAS, 344, 1000 Different Stellar Population Synthesis models 種族合成 デルの違 種族合成モデルの違い • Left) SED of models with TP-AGB and without TP-AGB. Right) Comparison of three stellar population synthesis models for galaxies at z=1.9, Maraston 2005, MNRAS, 362, 799 Maraston 2006, ApJ, 652, 85 Age-Metallicity degeneracy 年齢と金属量の縮退 • Older stellar population and metal-rich stellar population can have similarly red colors. Bruzual & Charlot 2003, MNRAS, 344, 1000 Indicators of age 年齢の指標 • Absorption line indices, Dn(4000), HdA index, are used to quantitatively examine spectra of galaxies Hd A index: after removing g contamination of Hd emission line using Hb, Hg emission line strength. Dn(4000) index Kauffmann et al., 2003, MNRAS, 341, 54 Effect of different stellar spectral model Effect of different metalicity (2.5solar, solar, 0.2solar) O,Bstars have weak Hd abs. Late-B early-F stars have strong Hd abs. Stellar population of galaxies 銀河の星種族 • The actual measured data (left) and constructed models (model) are compared on the Dn(4000), HdA index plane. The solid lines in the left panels l are tracks t k off burst b t star t formation f ti model d l and d the th points i t are continuus star formation model. Kauffmann et al., 2003, MNRAS, 341, 54 Models caluculated with BC2003 model. E Exponentially-decaying ti ll d i continnus ti star t formation f ti model + random “bursty” star formation. Kroupa IMF, 0.25-2 Zsolar。 Stellar population of galaxies 銀河の星種族 Kauffmann et al., 2003, MNRAS, 341, 54 Contribution from emission line / dust reddening 輝線の寄与 / ダ ダストによる赤化 トによる赤化 Estimated amount of dust reddening as a function of z-band absolute magnitude and Dn(4000). The colors of model SEDs (blue dots) and observed g galaxies ((black dots). ) Left p panels shows the colors without emission line correction and right panels with emission line correction Kauffmann et al., 2003, MNRAS, 341, 54 What does determine the observed relation between SMBH mass and spheroid mass ? Stellar populations in spheroids and formation model Color gradient of elliptical galaxies 楕円銀河の色勾配 • Elliptical galaxies show redder color in the central region. Peletier et al. 1990, AJ, 100, 109 Metallicity gradient vs. Age gradient 金属量勾配と年齢勾配 Kuntschner et al. 2010, MNRAS, 408, 97 Metallicity gradient vs. Age gradient 金属量勾配と年齢勾配 Kuntschner et al. 2010, MNRAS, 408, 97 Color gradient at higher redshifts 高赤方偏移での色勾配 Tamura et al. 2000, ApJ, 119, 2134 Galaxy merging and elliptical galaxies 銀河合体と楕円銀河 Duc et al., 2015, MNRAS, 446, 120 Elliptical galaxies and merger model 楕円銀河と銀河合体 デル 楕円銀河と銀河合体モデル • Disk-disk merging model to explain the nature of the spheroidal component. Hopkins et al. al 2008, 2008 ApJ, ApJ 679, 679 156 Elliptical galaxies and merger model 楕円銀河と銀河合体 デル 楕円銀河と銀河合体モデル Hopkins et al. 2009, ApJS, 181, 135 Metallicity gradient in merger model 銀河合体 デルでの金属量勾配 銀河合体モデルでの金属量勾配 Hopkins et al. 2009, ApJS, 181, 135 Cosmological Merging Model 宇宙論的な銀河合体 デル 宇宙論的な銀河合体モデル Naab et al. 2014, MNRAS, 444, 3357 Cosmological Merging Model 宇宙論的な銀河合体 デル 宇宙論的な銀河合体モデル Significant star formatin in situ Late gas-rich major merger Late gas-rich major merger Late dry major merger Late dry major merger Only minor mergers Naab et al. 2014, MNRAS, 444, 3357
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