A disk origin for inner stellar halo structures around the Milky Way - PowerPoint PPT Presentation

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” Monoceros, Eastern Banded Anticenter Stream (ACS) Structure (EBS) Triangulum-Andromeda (TriAnd) C. Slater

“Structures” / clouds / shells d ~ 8 kpc Anticenter Stream (ACS) d ~ 10 kpc Eastern Banded Structure (EBS) d ~ 8–12 kpc Monoceros / Giant Anticenter Stellar Stream (GASS) / Low Latitude Stream (LLS) Triangulum-Andromeda d ~ 15–30 kpc A13 d ~ 12–15 kpc Hercules-Aquila cloud d ~ 10–20 kpc d ~ 6–20 kpc Virgo over-density d ~ 16 kpc Eridanus-Phoenix (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 v GSR [km s − 1 ] 50 0 − 50 − 100 − 150 (M-giants) M-giants (RR Lyrae) 150 RR Lyrae 100 v GSR [km s − 1 ] 50 0 − 50 − 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 σ v R = σ v z = 25 km s − 1 v ϕ | = 185 km s − 1 | ¯ σ v ϕ ≈ 50 km s − 1

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