1. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 The Milky Way and its Satellite System in 3D Velocity Space: Its Place in the Current Cosmological Framework Dana I. Casetti - Yale University APOD (10/20/2007);copyright: Larry Landolfi

2. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Current Cosmological Framework:  CDM I. The makeup of the Universe, or the distribution of energy density of all “ matter ” WMAP - 2008 results today 13.7 Gyr ago map.gsfc.nasa.gov/news thus galaxy formation is governed by the dark-matter structure. Galaxy formation was initiated at around the epoch of reionization, (when first stars formed, ~ 400 Myr after Big Bang) => thus galaxy formation is governed by the dark-matter structure.

3. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Current Cosmological Framework:  CDM II. Galaxy formation There are two stages of collapse: - dark matter haloes (hierarchical built-up) - cooling of baryonic gas within haloes: if gas can cool efficiently (to below the halo virial temperature), then it will lose pressure support and can form a galaxy

4. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Current Cosmological Framework:  CDM VL1 - formation history and zoom-in at z=0

5. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Current Cosmological Framework:  CDM * Far-field Cosmology (large to moderate redshift):  CMB, galaxy clusters, large-scale structure of galaxies   CDM confirmed * Near-field Cosmology (redshift ~ 0):  the domain of resolved stellar systems: Milky Way, and possibly Andromeda   CDM challenged

6. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Why is the MW a challenge for  CDM models ? 1)Missing satellite problem: hundreds to thousands predicted, MW has ~ 20 (undetected? Are most of them dark matter haloes? Are some satellites formed via tidal interactions?) (undetected? Are most of them dark matter haloes? Are some satellites formed via tidal interactions?) 2)Predicted density profiles of subhaloes are cuspy (  ~ r -1 ); measured ones are less steep (if correct: possibility of warm dark matter!, but there is degeneracy between velocity anisotropy and slope of density, so we are unsure about the density profiles …) (if correct: possibility of warm dark matter!, but there is degeneracy between velocity anisotropy and slope of density, so we are unsure about the density profiles …) 3)Simulated dark-matter haloes are prolate ellipsoids; measurements of the MW dark matter halo indicate it is spherical, but results are controversial. 4) In models, disks of spiral galaxies are difficult to built and maintain thin, cold and extended.

7. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 -Dwarf satellite galaxies -Streams from tidally disrupted systems -Globular clusters The Galactic Gadabouts Excellent probes of the gravitational potential of the MW and of its subhalo structure Determine orbits and velocity dispersions or 3D velocities Need: radial velocities, distances and proper motions

8. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Proper Motions, Velocities and Uncertainties Current formal errors in absolute proper motions of stellar systems: Ground based: between 0.06 and ~1.5 mas/yr Space based (HST): between 0.04 and 0.5 mas/yr

9. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study I - Known satellites of the MW Bullock et al. 2010 Metz et al. 2008, 2009 -Spatial alignment of the traditional 11 dwarf sph. (Lynden-Bell 1976, 1982, Kunkel & Deemers 1976). -Newly found ultra-faint dwarfs follow this alignment (Metz et al. 2009). -Proper motions of 6 dwarf satellites indicate that their orbital angular momenta are aligned -> rotationally supported disk of satellites (Metz et al. 2008).

10. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study I - Known satellites of the MW Only 7 satellites have proper motions measured (with 0.04 to 0.25 mas/yr errors). HST and ground-based observations do not agree. Example: Fornax at ~ 140 kpc  Piatek et al. 2002 (before CTI correction) Dinescu et al. 2004  Piatek et al. 2006

11. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study I - Known satellites of the MW Only 7 satellites have proper motions measured (with 0.04 to 0.25 mas/yr errors). HST and ground-based observations do not agree. Example: Fornax at ~ 140 kpc  Piatek et al. 2002 (before CTI correction) Dinescu et al. 2004  Piatek et al. 2006

12. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study I - Known satellites of the MW Only 7 satellites have proper motions measured (with 0.04 to 0.25 mas/yr errors). HST and ground-based observations do not agree. Example: Fornax at ~ 140 kpc  Piatek et al. 2002 (before CTI correction) Dinescu et al. 2004  Piatek et al. 2006

13. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study I - Known satellites of the MW Example: The Magellanic Clouds HST-based proper motions (Kallivayalil et al. 2006, Piatek et al. 2009) indicate that the Clouds are unbound to the MW (if its mass implies a rotation of the LSR of 220 km/s), and likely unbound to each other … Recent ground-based results partially agree with HST results (Costa et al. 2009, Vieira et al. 2010).

14. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study II - Stellar Streams of the MW Example: The Sagittarius Dwarf Galaxy and its Tidal Stream G. Gilmore and R. Sword Ibata, Gilmore, Irwin 1994 P. Cseresnjes Found via radial velocities

15. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study II - Stellar Streams of the MW Example: The Sagittarius Dwarf Galaxy and its Tidal Stream Connecting 2MASS with SDSS along the Sagittarius tidal stream Belokurov et al. 2006, 2007, 2008, Majewski et al. 2003

16. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study II - Stellar Streams of the MW Example: The Sagittarius Dwarf Galaxy and its Tidal Stream Connecting 2MASS with SDSS along the Sagittarius tidal stream Belokurov et al. 2006, 2007, 2008, Majewski et al. 2003

17. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study II - Stellar Streams of the MW Example: The Sagittarius Dwarf Galaxy and its Tidal Stream The geometry of the orbit allows a direct determination of  LSR : the proper motions in longitude provides this.

18. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study II - Stellar Streams of the MW Example: The Sagittarius Dwarf Galaxy and its Tidal Stream Carlin 2010, Law et al. 2010 SA 71 SA 94 SA 93SA 117 SA 116 Sgr core

19. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 Case Study II - Stellar Streams of the MW Example: The Sagittarius Dwarf Galaxy and its Tidal Stream  LSR = 267 +- 23 km/s The traditional value of 220 km/s appears to be ruled out!

20. Diaspora in Cercetarea Stiintifica Bucuresti, 21-24 Sept. 2010 The Future -ESA: Gaia satellite -LSST (Large Synoptic Survey Telescope 8m class) -other more limited ground-based surveys, and a few more HST results