Name: Xiangxiang Xue PhD student Supervisor: HansWalter Rix

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Name Xiangxiang Xue (PhD
student)Supervisor Hans-Walter
RixHome institute National Astronomical
Observatories of China Current subject
probe Milky Ways rotation curve and dark halo
mass using kinematics of
Blue Horizontal-Branch stars from SDSSGeneral
interests the evolution and structure
of the Milky WayPractical expertise
how to use SDSS database, IDL, IRAF,MIDAS
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• Why estimate the Milky Ways halo mass?
• Mstar --- Mhalo ? baryon fraction
• Expected number of dark matter sub-halos
• Dynamics of the local group
• (e.g. M31 infall)

• Basic Approach
• Measure and model kinematics of kinematic
• tracers from SDSS
• Luminous and of known distance
• ? BHB stars

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• Steps
• Identifying BHB stars and getting line-of-sight
  velocity distribution P(vl.o.s , r)
• Modelling P(vl.o.s , r) to get Mtot(?rmax) and
  Mvir(halo)

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? Construct estimate of vcirc(r)
Pobs(Vl.o.s,/Vcirc) if vcirc(obs)180km/s