A disk origin for inner stellar halo structures around the Milky Way

Adrian Price-Whelan (Princeton University) ! adrn " adrianprw

Kathryn Johnston, Allyson Sheffield, Chervin Laporte, Maria Bergemann, Branimir Sesar, Ting Li, Chris Hayes, Steve Majewski, Rachael Beaton, Judy Cohen, Andy Tzanidakis Streams vs. “structures”

Grillmair & Carlin 2016 Streams vs. “structures”

C. Slater Streams vs. “structures”

Eastern Banded Monoceros, Structure (EBS) Anticenter Stream (ACS)

Triangulum-Andromeda (TriAnd)

C. Slater “Structures” / clouds / shells

Anticenter Stream (ACS) d ~ 8 kpc

Eastern Banded Structure (EBS) d ~ 10 kpc

Monoceros / Giant Anticenter Stellar Stream d ~ 8–12 kpc (GASS) / Low Latitude Stream (LLS)

Triangulum-Andromeda d ~ 15–30 kpc

A13 d ~ 12–15 kpc

Hercules-Aquila cloud d ~ 10–20 kpc

Virgo over-density d ~ 6–20 kpc

Eridanus-Phoenix d ~ 16 kpc (heliocentric) Accreted debris? Kicked out of disk?

D. Hendel A. Tzanidakis & C. Laporte Accreted debris? Kicked out of disk?

D. Hendel A. Tzanidakis & C. Laporte the Triangulum-Andromeda region the Triangulum-Andromeda region “Annoying Milky Way Foreground”

20

i 22

24 0 1 2 g − i Martin+2007 “Annoying Milky Way Foreground”

Monoceros

20

i 22 Triand 1 & 2 d⊙ ∼ 20 − 30 kpc 24 0 1 2 g − i Martin+2007 As an accretion event: Size + metallicity of TriAnd would imply ≳Sgr-mass progenitor

Triand 1

Triand 2

-2 -1.5 -1 -0.5 0 0.5 [Fe/H] Sheffield+2014 Sagittarius dsph metallicity distribution (RGB stars)

APOGEE survey RR Lyrae from Catalina Sky Survey

TriAnd P>0.8 M-giants 150 P 0.8 100  ] 1

50 0 [km s 50

GSR v 100 150 (M-giants)

M-giants 150 (RR Lyrae) RR Lyrae 100 ] 1

50 0 [km s 50

GSR v 100 150 160 150 140 130 120 110 100 10 25 40 l [deg] N

Price-Whelan+2015 Monoceros & A13 RR Lyrae from Catalina Sky Survey

A13 Monoceros/GASS

TriAnd Sheffield, Price-Whelan+2018 TriAnd, Monoceros, A13 have many K/M giants, few (if any) RR Lyrae: suggests a stellar population unlike any of the dwarf satellites of the Milky Way

The Milky Way disk is metal rich: few RR Lyrae, many K/M giants - could these features have originated in the disk? but…very far from disk

Johnston, Price-Whelan+2017 Detailed chemistry of A13 & TriAnd Bergemann,…,Price-Whelan+2018 0.5

0.0

[Na/Fe] -0.5

-1

-3 -2 -1 0 1 [Fe/H]

Bergemann,…,Price-Whelan+2018 Outer disk open clusters 0.5

0.0 MW disk [Na/Fe] -0.5

-1

-3 -2 -1 0 1 [Fe/H]

Bergemann,…,Price-Whelan+2018 Outer disk open clusters 0.5

0.0 MW disk [Na/Fe] -0.5 Sgr

Fornax

-1

-3 -2 -1 0 1 [Fe/H]

Bergemann,…,Price-Whelan+2018 Outer disk open clusters 0.5

TriAnd / A13

0.0 MW disk [Na/Fe] -0.5 Sgr

Fornax

-1

-3 -2 -1 0 1 [Fe/H]

Bergemann,…,Price-Whelan+2018 3D kinematics with Gaia TriAnd stars Rotating with the disk, slightly slower than solar circular velocity

−1 σvR = σvz = 25 km s −1 |v¯ϕ | = 185 km s −1 σvϕ ≈ 50 km s Summary Summary

Many of the “structures” identified as streams, clouds, or halo over- densities are associated with or originate from the Galactic disk, but now at extreme radii/heights above disk Disk Accretion

Eastern Banded Structure (EBS) Hercules-Aquila

Anticenter Stream (ACS) Eri-Phoenix (?)

Monoceros / GASS Virgo (?)

TriAnd

A13 Disk Accretion Talk by Chervin Laporte Eastern Banded Structure (EBS) Hercules-Aquila

Anticenter Stream (ACS) Eri-Phoenix (?)

Monoceros / GASS Virgo (?)

TriAnd

A13 This talk Summary

Many of the “structures” identified as streams, clouds, or halo over- densities are associated with or originate from the Galactic disk, but now at extreme radii/heights above disk

These stars could have been “kicked out” as a result of interactions with Sagittarius and the LMC Laporte+2017 Summary

Many of the “structures” identified as streams, clouds, or halo over- densities are associated with or originate from the Galactic disk, but now at extreme radii/heights above disk

These stars could have been “kicked out” as a result of interactions with Sagittarius and the LMC

These features are tracers of dark matter in the outer disk, and will constrain interaction history of the Milky Way and Sagittarius Some relevant work:

Newberg+2002

Martin+2007, 2014

Sheffield, Johnston+2014

Xu, Newberg+2015

Price-Whelan, Johnston, Sheffield+2015

Li, Sheffield+2017

Laporte+2017

Johnston, Price-Whelan+2017

Bergemann, Sesar+2018

Sheffield, Price-Whelan+2018

Hayes+2018 Extra slides TriAnd Sgr LMC

SMC

Kirby+2013 Kirby+2013 K/M Giants

RR Lyrae 0.8

0.4

[Mg/Fe] 0.0

-0.4

-3 -2 -1 0 1 [Fe/H]

Bergemann,…,Price-Whelan+2018 Bergemann,…,Price-Whelan+2018