The impact of Sagittarius on the disk of the Milky Way

Transcription

1 The impact of Sagittarius on the disk of the Milky Way David Law James Bullock (UC Irvine)

2 The impact of Sagittarius on the disk of the Milky Way Chris Purcell (Irvine U Pittsburgh) Erik Tollerud (Irvine)

3 Near-Field Cosmology Detailed observations of MW & Local Group to inform general models of galaxy formation. Milky Way How do we make thin disks like the MW in LCDM? Bars? Spirality? (Even harder questions) NASA/JPL

4 Missing Satellites Problem Bullock/Geha Diemand, Kuhlen, Madau

5 Halo Streams & Substructure Milky Way looks hierarchical Bullock & Johnston 2005

6 Halo Streams & Substructure Substructure within ~20 kpc of Galactic Center! 20 Juric 08 Virgo overdensity 10 z (kpc) 0-10 Monocoros: R~20kpc, z~4kpc -20 Structure w/in ~20 kpc of Galactic Center! R (kpc) Bullock & Johnston 2005

7 Ghosts of past mergers... Rigid (growing) disk potential Milky Way (David Law) Bullock & Johnston 05

8 What do all of these mergers do to the disk? Sgr Monoceros Ring

9 Cosmological Context Stewart et al. 08 Ave # mergers per halo Msun halo Accreted dark halo mass (Msun)

10 Cosmological Context Stewart et al. 08 > Msun mergers - HAVE NOT happened Ave # mergers per halo Msun halo Accreted dark halo mass (Msun)

11 Cosmological Context Ave # mergers per halo Stewart et al Msun halo Msun mergers ~70% of the time ~1 over last 10 Gyr Accreted dark halo mass (Msun)

12 Cosmological Context Stewart et al Msun mergers Purcell et al. 09 Ave # mergers per halo Msun halo Accreted dark halo mass (Msun) Initial Remnant - Heat disks, don t destroy them - Milky Way is probably too cold to have had one. MW uncommonly quiescent. (Purcell, JSB, Kazantzidis 09).

13 Cosmological Context Ave # mergers per halo Stewart et al Msun halo ~10 10 Msun mergers - ALWAYS happen - Typically ~6 in last 10 Gry Accreted dark halo mass (Msun)

14 Cosmological Context Ave # mergers per halo Stewart et al Msun halo ~10 10 Msun mergers - ALWAYS happen - Typically ~6 in last 10 Gry Kazantzidis, JSB et al Accreted dark halo mass (Msun)

15 Cosmological Context Ave # mergers per halo 10 9 Stewart et al Msun halo Accreted dark halo mass (Msun) ~10 10 Msun mergers - ALWAYS happen - Typically ~6 in last 10 Gry Kazantzidis, JSB et al Create interesting disk structures - Rings, spirals, flares - Detailed predictions depend on orbits, masses, timing, etc.

16 Sgr Dwarf Progenitor? Nierderste-Ostholt et al. 2010: (~70% of light in stream) L Sgr total 108 L M M

17 Sgr Dwarf Progenitor? 12 Conroy & Wechsler 2009 Nierderste-Ostholt et al. 2010: (~70% of light in stream) log[m star (M sun )] z=0 MW z=2 L Sgr total 108 L M M log[m host (M sun )]

18 Sgr Dwarf Progenitor? 12 Conroy & Wechsler 2009 Nierderste-Ostholt et al. 2010: (~70% of light in stream) log[m star (M sun )] z=0 MW z=2 Sgr Progenitor log[m host (M sun )] L Sgr total 108 L M M M vir M

19 Sgr Dwarf Progenitor? 12 Conroy & Wechsler 2009 Nierderste-Ostholt et al. 2010: (~70% of light in stream) log[m star (M sun )] z=0 MW z=2 Sgr Progenitor log[m host (M sun )] L Sgr total 108 L M M M vir M M Sgr total M disk MW

20 30 million particle disk + live halo Purcell, JSB, Tollerud 2010

21 Stable to secular instabilities Purcell, JSB, Tollerud 2010

22 Light Sgr Model Mv = 1.5e10 Msun Purcell, JSB, Tollerud 2010

23 Light Sgr Model Mv = 1.5e10 Msun Purcell, JSB, Tollerud 2010

24 The impact of Sagittarius on the disk of the Milky Way Law et al. Purcell et al. Rigid halo, rigid disk, no dark matter in Sgr Fully self-consistent

25 Purcell, JSB, Tollerud 2010

26 Intermediate-scale spiral structure, similar to MW??? Purcell, JSB, Tollerud 2010

27 Intermediate-scale spiral structure, similar to MW Sgr Sgr Monoceros Ring Purcell, JSB, Tollerud 2010

28 Intermediate-scale spiral structure, similar to MW Sgr Sgr Monoceros Ring Purcell, JSB, Tollerud 2010

29 Intermediate-scale spiral structure, similar to MW Sgr Sgr Monoceros Ring Purcell, JSB, Tollerud 2010

30 Heavy Sag, M=3.e10Msun Sgr Monoceros Ring Purcell, JSB, Tollerud 2010

31 Milky Way Scale height ~ 400 pc Velocity Ellipsoid ~ (35, 32, 20) km/s Heavy Sag, M=3.e10Msun Scale height = 500 pc Velocity Ellipsoid = (37, 27, 20) km/s

32 Did the Sag impact Create Monoceros Ring? Light Sag M = 1.5e10 Msun Heavy Sag M = 3.e10 Msun

33 Conclusions Purcell, JSB, Tollerud 2010 Sagittarius = an architect of structure in the Galaxy

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37 Halo Streams & Substructure Halo substructure compares well to LCDM e.g. Bell et al. (2008) David Law Bullock & Johnston 05 MW data + models engineered to match data Random LCDM realization

38 Light Sag M = 1.5e10 Msun Simulation Heavy Sag M = 3e10 Msun Simulation

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41 Heavy Sag M = 3.e10 Msun Simulation Milky Way Disk NASA/JPL-Caltech Sgr Sgr Monoceros Ring? Scale height = 510 pc Velocity Ellipsoid = (37, 27, 20) km/s Scale height ~ 400 pc Velocity Ellipsoid ~ (35, 32, 20) km/s

42 Near-Field Cosmology What do all of these mergers do to the disk? Sgr Monoceros Ring

43 Near-Field Cosmology Halo Streams & Substructure Bullock & Johnston 2005