Renegades in the Solar neighborhood

Transcription

1 Title Renegades in the Solar neighborhood Ana Bonaca ITC Fellow Harvard University // Charlie Conroy // // Andrew Wetzel //

2 Origin of the halo stars: In situ Eggen, Lynden-Bell & Sandage (1962) Accretion Searle & Zinn (1978)

3 Origin of the halo stars: In situ Eggen, Lynden-Bell & Sandage (1962) Accretion Searle & Zinn (1978) Fraction of total halo Distance (kpc) Fraction of total halo Zolotov et al. (2009) Recent accretion Ancient accretion 0.2 In situ Distance (kpc)

4 Goal: Goal Explore the structure of the local stellar halo, in hope of finding clues to its origin.

5 Exploring the Galactic 6-D phase space with: z Gaia / TGAS Brown et al. (2016) Michalik et al. (2015) x RAVE / RAVE-on Kunder et al. (2017) Casey et al. (2016)

6 Kinematic disk / halo decomposition

7 Kinematic disk / halo decomposition Halo: Halo Disk

8 Metallicity distribution function Disk Halo Probability [Fe/H]

9 Metallicity distribution function Disk Halo Probability [Fe/H] There are a lot of metal-rich stars in the halo.

10 Metallicity distribution function RAVE-on APOGEE Disk Halo 1.5 Probability 1.0 Probability [Fe/H] [Fe/H] There are a lot of metal-rich stars in the halo.

11 Chemical abundance patterns Metal rich halo follows the disk abundance pattern.

12 Orientation of angular momenta z x

13 Orientation of angular momenta z Angular momentum orientation angle: x

14 Orientation of angular momenta z Angular momentum orientation angle: 0.05 Disk x 0.04 Halo: [Fe/H] > 1 Halo: [Fe/H] 1 Probability Metal-rich halo is preferentially prograde L orientation (deg)

15 Toy model of the Galaxy positions: TGAS + RAVE-on velocities: Bensby et al. (2003)

16 Toy model of the Galaxy positions: TGAS + RAVE-on velocities: Bensby et al. (2003)

17 Toy model of the Galaxy positions: TGAS + RAVE-on velocities: Bensby et al. (2003)

18 Toy model of the Galaxy positions: TGAS + RAVE-on velocities: Bensby et al. (2003)

19 Toy halo, kinematically defined

20 Toy halo, kinematically defined The metal poor halo is isotropic.

21 Toy halo, kinematically defined The metal poor halo is isotropic.

22 Halo origin hypotesis Metal-poor halo: isotropic, hence accreted Metal-rich halo: preferentially prograde, hence formed in situ

23 Milky Way vs Latte ~ Milky Way Latte Wetzel et al. (2016)

24 Milky Way vs Latte ~ Milky Way Latte Wetzel et al. (2016)

25 The Milky Way / Latte comparison

26 The Milky Way / Latte comparison

27 The Milky Way / Latte comparison

28 The origin of Solar neighborhood in Latte

29 The origin of Solar neighborhood in Latte

30 The origin of Solar neighborhood in Latte Most halo stars migrated to the Solar neighborhood.

31 The origin of Solar neighborhood in Latte Most halo stars migrated to the Solar neighborhood.

32 Halo origin from stellar ages Latte prediction: At a given age, the in situ halo is more metal rich than the accreted halo.

33 Halo origin from stellar ages Apply! Gaia Sprint 2017 Heidelberg Latte prediction: At a given age, the in situ halo is more metal rich than the accreted halo.

34 Summary Stellar halo in the Solar neighborhood has an isotropic, metal-poor component, and a prograde, metal-rich component.

35 Stellar Summary halo in the Solar neighborhood has an isotropic, metal-poor component, and a prograde, metal-rich component. Comparison to simulations suggests an accretion origin for the metal-poor, and an in situ origin for the metal-rich component.