銀河物理学特論 I G l ti A t h i I Galactic Astrophysics I I

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