How Massive is the Milky Way?

Transcription

1 How Massive is the Milky Way? See also: Klypin et al. (2002) Simon s talk Matthias Steinmetz Astrophysical Institute Potsdam

2 Overview Spectroscopic Surveys of the MW Geneva-Copenhagen, SDSS, RAVE Mass estimates Using cosmological simulations for data interpretation Do we have consistency between different mass estimates? 2 Kingston, June 15-19,

3 GCS, RAVE and SEGUE are complimentary Kingston, June 15-19, SEGUE selected pointings deep exposures low resolution (R=2000) large wavelength coverage northern hemisphere no repeats Geneva-Copenhagen Survey volume limited, F & G stars 3 repeats for each star stars with Hipparcos parallaxes RVs via correlations RAVE wide angular coverage intermediate depth medium resolution (R=7500) limited wavelength coverage southern hemisphere 10% repeats 3

4 Kingston, June 15-19, The RAVER survey Spectroscopic high latitude survey of the MW 9 < I < spectra for stars GAIA spectral range and resolution Ca triplet region ( Å) R eff =7500 Scheduled operation: dF MOS on UKST at Siding Spring 7 nights per lunation up to 8/ nights per lunation since 8/2005 Goal: 1 Million spectra Typical RV error: 2 km/s 50% of the stars have 3D velocity errors better than 20 km/s 4

5 5 Kingston, June 15-19,

6 6 Kingston, June 15-19,

7 7 Kingston, June 15-19,

8 Comparison of RV-surveys 8 Kingston, June 15-19,

9 9 Kingston, June 15-19,

10 10 Kingston, June 15-19,

11 11 Kingston, June 15-19,

12 12 Kingston, June 15-19,

13 Compare SDSS stellar mass function with DM halo mass function M MW = M Forero et al 13 Kingston, June 15-19,

14 Compare K-band luminosity function with DM halo mass function f b =0,18 Forero et al 14 Kingston, June 15-19,

15 TF + mass-ang.-momentum-relation In ΛCDM halos, disks contain a larger fraction of the total specific angular momentum than of baryon mass! 15 Kingston, June 15-19, Fraction of baryons transformed into stars Ratio between disk and halo specific angular momenta Navarro & MS 2000

16 TF + mass-ang.-momentum-relation 16 Kingston, June 15-19, Fraction of baryons transformed into stars Ratio between disk and halo specific angular momenta Piontek & MS

17 The Escape Speed of the Milky-Way Smith, et al 2007 Leonard & Tremaine (1990): near escape velocity: f ( ε ) ε k ε = ( 2 2 v ) e v 17 Kingston, June 15-19,

18 The Mass of the Milky-Way Smith et al., Kingston, June 15-19,

19 The Escape Velocity of the Milky-Way 498 < v esc < 608 km/s For an adiabatically contracted NFW dark halo: Kingston, June 15-19, Smith et al 2007 M MW M MW = = M Non contracted NFW dark halo: M 19

20 V circ and V esc from SDSS M no AC = M AC = M M RAVE Xue et al Kingston, June 15-19,

21 Dark Matter in the Milky Way Kingston, June 15-19, Dark Mass within the Solar Circle Constraint from universal baryon fraction Dark mass constraint from Oort limit Halo Mass (Circular Velocity) Eke, Navarro & Steinmetz

22 Mass of the MW dark matter halo Abadi et al 22 Kingston, June 15-19,

23 Velocity dispersion vs radius Battaglia et al Kingston, June 15-19,

24 Anisotropy of stellar and DM halo Kingston, June 15-19, Dark matter halo and stellar halo exhibit quite different structural properties Abadi et al

25 v v Disk Pro Tully Fisher DM in disks Con Abundance of disk galaxies Abadi et al Kingston, June 15-19,

26 Estimating v vir via satellites MW M31 26 Kingston, June 15-19,

27 What does that mean for the MW as a typical LCDM galaxy? Is there an inconsistency between stellar dynamics, timing arguments and statistics? We need better galaxy formation models Kingston, June 15-19, M M Only ~20% of halos suitable hosts >75% of the baryons in the MW are unaccounted for Disk size: access to the full angular momentum reservoir M M MW would rather untypical or over abundant Local group timing argument 27