The Local Group

The Local Group35 - 40 members

M31, and its satellites (red)

Milky Way, and its satellites (blue)

Isolated dwarfs (blue)

THE LOCAL GROUP

Mass Length Time

Stellar Archaeology and Galaxy Genesis

● LR kinematic and general metallicity measures of main Galactic structures

● detailed HR abundances of these to trace chemical development over time

● LR analysis of surviving nearby galaxies and streams

● exploit synergy with GAIA to break degeneracies

Mike Irwin

DE + DM + VM

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Credit: Matthias Steinmetz

age in Gyr

mass

fra

ctio

nAbadi, Navarro, Steinmetz & Eke 2003

Fine structure of simulated galaxies

thin

dis

kth

ick

dis

ksp

hero

id

Galaxy substructure and satellite accretion

38 30 23

Bullock & Johnston 2005

300 x 300 kpc

CDM modelspredict large-scalesubtructure in Lgalaxies like M31 and MW

*

Near-field cosmology - some key questions

● where are the missing satellites?● are dark matter profiles universal?● what is the extent nature and spatial

distribution of dark matter?● how were the Galaxy and M31 constructed?

are they typical disk galaxies?● what was the role of accretion in the

formation of the halo, disk, bulge?● what was the detailed chemical enrichment

history of the stellar components?

Galactic Science

clusters galaxies

singlestellar componentsno DM ?

mulitplestellarcomponentsDM ?

missing satellites ??

AndXIAndXII

AndXIII

Belokurov et al. 2006

AndXIV

AndXVAndXVI

Missing satellites & Halo DM lumpiness

Pal5 : Odenkirchen et al (2003)

An accretion into the MW 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)

DA

RT

Canis-Major and the Monoceros Ring

DA

RT

Galactic Science

● chemo-dynamic structure of Galactic components - interface between disk, bulge/bar, halo - ancient dissolved and surviving substructures

● fossil record of chemical evolution of stellar pops - chemical signature of ancient accretions - properties of metal-poor popIII stars

● evolutionary history of stellar components - IMF, SFH, tagging the chemical development - the role of star clusters

● linking the Bulge to the high Z universe ● detailed chemo-dynamics of surviving satellites

What do you need - I ?

● wide field well calibrated imaging optical -> NIR

● north: SDSS ugriz, WFCAM UKIDSS zyJHK● south: Skymapper, VST, CTIO 4m DES, VISTA ● all-sky: 2MASS calibration and pathfinder● GAIA: proper motions and parallaxes ● large area stellar spectroscopy (million stars)● automate majority of processing and analysis

=> logg, Teff, vel, [m/H]

What do you need - II ?

● large telescope with a wide fov eg. degrees diam

● 1000-4000 fibres to exploit target surface density

● survey selected regions totalling ~1000 sq deg● larger systematic survey find new structures● LR -> Mgb 4800-5500A and CaT 8150-8850A

vels to < 10 km/s; [Fe/H] to 0.1-0.2 dex; limited chemical tagging e.g. [alpha/Fe] ?

● synergy with GAIA => LR to ~V=20 => full 6D kinematic phase space information

GA substructure with LAMOST +

• dsphs and “dark” satellites eg. UMaI, UmaII ......

• tidal streams eg. GCs; dSphs; orphan streams

• open clusters and unbound debris

• known halo/disk sub-structures eg. Triang-And-Perseus; Sgr stream; Hercules-Aquila cloud; Arcturus group .......

• outer disk eg. warp -v- Canis Major edge of, outer spiral arm structure

DA

RT

LAMOST and GA competition

Summary

● large area spectroscopic studies of nearby galaxies are needed to test cosmological predictions on low-mass scales– nature and distribution of dark

matter– detailed formation history of galaxies

● GAIA will revolutionise this field, but will lack detailed chemical information, as well as accurate radial velocities