銀河考古学:
近傍銀河宇宙から探る銀河形成史
Galactic Archaeology:
Deciphering history of galaxy
formation from the local universe
千葉柾司
（東北大学）
Masashi Chiba
(Tohoku Univ)
1
Local Universe
Andromeda
Sendai
Milky Way
Our Galaxy
Understanding stellar populations
Formation and evolution of the Galaxy
gas
stars
Galaxy formation
and evolution
high-z universe
(snapshots of
various galaxies)
complementary
stellar system
in local universe
(tracing evolution
of a galaxy)
Bekki & Chiba 2001
Galactic astronomy based on
resolved stellar system
• Photometry ⇒ magnitude, color (→ color-magnitude
diagram : CMD）
• Spectroscopy ⇒ metallicity (→ age), chemical
abundance pattern (→ star formation history & chemical
evolution), radial velocity
• Astrometry ⇒ proper motion & distance (→ information
on 6-dimensional phase space)
Spatial structure, dynamical structure,
star formation, and chemical evolution
of the stellar system
⇒ galaxy formation and evolution
Old galactic components
halo star
bulge
thick disk
inner halo
Thin disk
: age < 10 Gyr
Thick disk, Halo : age > 10 Gyr
Bulge
: age ~ 10 Gyr
globular cluster
outer halo
CMD of the globular cluster : M3
AGB
HB
V
RGB
BS
TO
MS
SG
Formation history of
a globular cluster
B－V
The Sun
Fossil records of galaxy formation
⇒ Galactic Archaeology
Cosmic star formation history
Madau & Dickinson (2014)
Star Formation Rate Density evolution
Stellar Mass Density evolution
9
Milky Way & Galactic satellites
10
Local Group
11
HST photometry of LG galaxies
Leo I (dSph)
Andromeda Galaxy
Substructure in M31’s halo
(Ferguson et al. 2002)
Northern Spur
M32
G1 Clump
Stream
14
ACS/HST photometry of M31’s halo
(using 120 HST orbits!)
V=28mag
V=30mag
Comparison with ΛCDM model
High-resolution numerical simulation
for a galactic collapse
(green: M=108-1010Msun, T>104K)
Moore et al. 2005, astro-ph/0510370
z=12
z=0
Outline
1. Kinematics and dynamics of a stellar
system
2. Stellar populations and chemical evolution
3. The nature of Galactic components
4. Galactic dark matter
5. Formation of the Galaxy
6. Formation and evolution of Local Group
galaxies
17
References
•
•
•
•
Galactic Dynamics (2008) by Binney &
Tremaine (Princeton)
Nucleosynthesis and Chemical Evolution of
Galaxies (1997) by Pagel (Cambridge)
Evolution of Stars and Stellar Populations
(2005) by Salaris & Cassisi (Wiley)
シリーズ現代の天文学
４：銀河Ｉ, ５：銀河ＩＩ, ７：恒星 (日本評論社)
•
銀河考古学（Galactic Archaeology）（2015）
by MC （日本評論社）
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