Matthias Steinmetz (AIP)

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How Massive is the Milky Way?

• Matthias Steinmetz (AIP)

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Compare K-band luminosity function with DM halo
mass function
M? km/s
Forero et al 2009
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Compare K-band luminosity function with DM halo
mass function
fb0,18
Forero et al 2009
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Dark Matter in the Milky Way
Dark Mass within the Solar Circle
Dark mass constraint from Oort limit
Constraint from universal baryon fraction
Eke, Navarro Steinmetz 2001
Halo Mass (Circular Velocity)
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Mass of the MW dark matter halo
Abadi et al 2009
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The Tully-Fisher Relation

• Slope and scatter OK
• Zero point offset
• halos too concentrated
• high stellar mass-to-light ratios

Eke, Navarro Steinmetz 2001
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The Escape Speed of the Milky-Way
Smith, Rutchi et al 2007
Leonard Tremaine (1990) near escape velocity
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The Mass of the Milky-Way
Smith et al, 2007
CDM simulations Dark Matter
CDM simulations Stars
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The Escape Velocity of the Milky-Way
For an adiabatically contracted NFW dark halo
M?
vvir 142 km/s
Smith et al 2007
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Vcirc and Vesc from SDSS
RAVE
Xue et al 2008
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Estimating vvir via satellites
MW
M31
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In situ stars that formed in the most massive
progenitor
accreted stars that formed in satellites
Abadi et al 2005
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Accreted stars only!
Sersic law
Abadi et al 2005
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Abadi et al 2005
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Velocity dispersion vs radius
Battaglia et al 2005
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Anisotropy of stellar and DM halo
Dark matter halo and stellar halo exhibit
quite different structural properties
Abadi et al 2005
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• v200 0.5 vDisk
• Pro
• Tully Fisher
• DM in disks
• Con
• Abundance of disk galaxies

Abadi et al 2005
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NFW halos HI distribution
M?
Kalberla et al 2007
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Halo potential and hyper velocity stars
Cosmological prediction for MW potential
Inferred from MW dynamics
Abadi et al 2008
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High velocity stars
Abadi et al 2008
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HVS disrupted satellites?
Abadi et al 2008
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HVS disrupted satellites?
Abadi et al 2008
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What does that mean for the MW as a typical LCDM
galaxy?

• Vc 200 km/s (as favored by SAMs)
• Luminosity function TF relation
• Only 20 of halos suitable hosts
• 90 of the baryons in the MW unaccounted for
• Disk size access to the full angular momentum
  reservoir
• Vc 140 km/s
• MW would rather untypical or over abundant