Download Galactic archaeology

Galactic archaeology
Rodrigo Ibata
Observatoire de Strasbourg
Fine structure of simulated galaxies
age in Gyr
thin disk
thick disk
mass fraction
spheroid
Abadi, Navarro, Steinmetz & Eke 2003
The big questions
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Where are/are there missing satellites?
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Are dark matter profiles universal?
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What is the fine distribution of dark matter?
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How did the galaxy build up?
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What was the role of accretion in the
formation of the halo, disk, bulge?
What was the detailed chemical enrichment
history?
Uniqueness of the MW & Local
Group
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Kinematic surveys of 1000s of stars possible
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dynamics of fine structure
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Detailed chemistry
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(chemical tagging of stars?)
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Age-dating of stellar populations
Halo structure: streams!
J. Bullock
Halo streams
Majewski et al. 1994
Majewski et al. (2003)
SDSS colour-selected stars
Newberg et al. (2001)
also SDSS RRLyraes
Ivezic et al.
Quest RRLyraes
Vivas et al.
Substructure in the disk: The Monoceros
ring
SDSS: Newberg et al. (2002)
then Yanny et al. (2003), Ibata et al.
(2003), Crane et al. (2003), RochaPinto et al. (2004), Frinchaboy et al.
(2004), Peñarrubia et al. (2005)
➙ Accretion stream?
• 120°<l<240°
• |b|<30°, both hemispheres
• 15 < DGC < 20 kpc
• almost circular orbit
• σvr ~ 20-30 km/s
• several globular and open
clusters coincide with orbit
An accretion into the disk?
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Heliocentric
distance:
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TRGB: 7.2 ± 0.3 kpc
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4-10 Gyr population
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σ=12km/s
(Martin et al 2004, 2005,
Bellazzini et al. 2005)
Outer galaxy in Red Clump stars
Canis Major
TriAnd
Monoceros
Ring
G. Lewis
c.f. Andromeda...
Red RGB
125 kpc
Blue RGB
Qualitatively consistent with predictions (e.g.
Abadi et al. 2003)
95 kpc
Outer disk substructure
Missing satellites?
Klypin et al. (1999)
Moore et al. (2000)
Bullock et al. (2000)
Somerville (2001)
Stoehr et al. (2002)
Kravtsov et al. (2004)
Moore et al. 2000
New M31 satellites: Metal-poor
Neighbors within 2”
8”
CFHT/MegaCam (Martin et al. 2006 in prep)
And III
New M31 satellites: Metal-rich
Neighbors
Neighborswithin
within12”
8”
How can we detect completely
dark structures?
By the heating of globular cluster streams!
No dark lumps
lumpy DM halo
Ibata, Lewis, Irwin, Quinn (2002)
existence proof: Pal5
Pal5 : Odenkirchen et al (2001)
Dehnen, simulation
GAIA
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~1 billion stars surveyed to
V~20
proper motions: 10μas at V=15
velocities for 108 stars (210km/s) to V=17
~10% accuracy parallaxes to
10kpc
However, no chemical “fingerprinting”
Chemical tagging...
Venn et al. 2004
Conclusions
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Studies of nearby galaxies are needed to test
cosmological predictions on low-mass scales
–
dark matter distribution (cusps)
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existence of dark satellites
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detailed formation history of galaxies
GAIA will revolutionise this field, but will lack
detailed chemical information, as well as accurate
radial velocities
Chemistry (e.g., from ARGOS or WFMOS
surveys) may prove to be key additional info to
unravel the mess left after all the merging