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Galactic archaeology Rodrigo Ibata Observatoire de Strasbourg.
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Transcript of Galactic archaeology Rodrigo Ibata Observatoire de Strasbourg.
![Page 1: Galactic archaeology Rodrigo Ibata Observatoire de Strasbourg.](https://reader031.fdocuments.net/reader031/viewer/2022032703/56649d205503460f949f4730/html5/thumbnails/1.jpg)
Galactic archaeology
Rodrigo IbataObservatoire de Strasbourg
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age in Gyr
mass
fra
ctio
nAbadi, Navarro, Steinmetz & Eke 2003
Fine structure of simulated galaxies
thin
dis
kth
ick
dis
ksp
hero
id
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The big questions
● Where are/are there missing satellites?● Are dark matter profiles universal?● What is the fine distribution of dark
matter?● How did the galaxy build up?● What was the role of accretion in the
formation of the halo, disk, bulge?● What was the detailed chemical
enrichment history?
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Uniqueness of the MW & Local Group
● Kinematic surveys of 1000s of stars possible
● dynamics of fine structure
● Detailed chemistry● (chemical tagging of stars?)
● Age-dating of stellar populations
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Halo structure: streams!
J. Bullock
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Halo streams
Majewski et al. 1994
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Majewski et al. (2003)
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SDSS colour-selected starsNewberg et al. (2001)
also SDSS RRLyraesIvezic et al.
Quest RRLyraesVivas et al.
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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), Rocha-Pinto et al. (2004), Frinchaboy et al.
(2004), Peñarrubia et al. (2005)
• 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
➙ Accretion stream?
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An accretion into the disk?
● Heliocentric distance:
– TRGB: 7.2 ± 0.3 kpc
● 4-10 Gyr population
● σ=12km/s
(Martin et al 2004, 2005,Bellazzini et al. 2005)
Outer galaxy in Red Clump stars
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Canis Major
TriAnd
Monoceros Ring
G. Lewis
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Blue RGB Red RGB1
25
kp
c
95 kpc
c.f. Andromeda...
Outer disk substructure
Qualitatively consistent with predictions (e.g. Abadi et al. 2003)
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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
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New M31 satellites: Metal-poorNeighbors within 8”
And III
Neighbors within 2”
CFHT/MegaCam (Martin et al. 2006 in prep)
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Neighbors within 12”Neighbors within 8”
New M31 satellites: Metal-rich
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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)
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existence proof: Pal5
Pal5 : Odenkirchen et al (2001)Dehnen, simulation
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GAIA
● ~1 billion stars surveyed to V~20
● proper motions: 10μas at V=15
● velocities for 108 stars (2-10km/s) to V=17
● ~10% accuracy parallaxes to 10kpc
● However, no chemical “finger-printing”
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Chemical tagging...
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Venn et al. 2004
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Conclusions
● Studies of nearby galaxies are needed to test cosmological predictions on low-mass scales– dark matter distribution (cusps)
– existence of dark satellites
– 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