Near Field Cosmology

Vasily Belokurov, Institute of Astronomy, Cambridge UK Pairing Dark Matter halos and astrophysical objects

Galaxy cluster Milky Way Dwarf ? ? ? ?

1014 M⊙ 1012 M⊙ 1010 M⊙ 108 M⊙ 106 M⊙

Low-mass stars live forever ⊙ stellar luminosity, L stellar luminosity,

stellar mass, M⊙ Low-mass stars live forever

⊙ massive stars are hotter L M 3.5 / and burn brighter stellar luminosity, L stellar luminosity,

stellar mass, M⊙ Low-mass stars live forever

⊙ massive stars are hotter L M 3.5 / and burn brighter M stellar life t but at this rate… / L stellar luminosity, L stellar luminosity,

stellar mass, M⊙ Low-mass stars live forever

⊙ massive stars are hotter L M 3.5 / and burn brighter M stellar life t but at this rate… / L

2.5 they burn faster! t M / stellar luminosity, L stellar luminosity,

stellar mass, M⊙ Low-mass stars live forever

⊙ massive stars are hotter L M 3.5 / and burn brighter M stellar life t but at this rate… / L

2.5 they burn faster! t M / stellar luminosity, L stellar luminosity, ~Hubble time

stellar mass, M⊙ Early Universe at home

Big Bang

Pink Floyd’s first album Early Universe at home

Big Bang

Hubble Deep Field

Pink Floyd’s first album Early Universe at home

Big Bang Oldest Stars in Our Galaxy

Hubble Deep Field

Pink Floyd’s first album Early Universe at home

Big Bang Oldest Stars Star-formation histories of Galactic dwarfs in Our Galaxy

Weisz et al, 2014

Hubble Deep Field

Pink Floyd’s first album Stellar and Dark Halos are alike

Dark Matter halo Stellar and Dark Halos are alike

Dark Matter halo Stellar halo

Andrew Cooper Stellar halo is Stellar halo is

satellites Stellar halo is

satellites

streams Stellar halo is

satellites

scramble

streams Information content

• Satellites: constraints on the lowish end of the DM mass function, targets for indirect searches

• Streams: shape of the DM distribution, granularity of the DM distribution - unique probes of DM

• Scramble: accretion history, mixing efficiency - crucial for direct searches Needle in the haystack

SDSS image cutout Needle in the haystack

dynamics+ stellar evolution+ simulations+ big data SDSS image cutout Three predictions of ɅCDM

for sub-structure around the Milky Way

1. Hundreds of dwarf galaxy satellites

2. Most massive dwarfs have satellites of their own

3. Most low-mass sub-halos are forever dark Prediction 1 Hundreds of dwarf galaxy satellites around the Milky Way Galactic dwarf satellite count

LMC

1/40 LMW Invisible galaxies

Leo I Bootes I Horologium I

8,000 times fainter 2,000,000 times fainter 100,000,000 times fainter then the Milky Way then the Milky Way then the Milky Way discovered with SDSS discovered with DES Invisible galaxies

Leo I Bootes I Horologium I

8,000 times fainter 2,000,000 times fainter 100,000,000 times fainter then the Milky Way then the Milky Way then the Milky Way discovered with SDSS discovered with DES Invisible galaxies

Leo I Bootes I Horologium I

8,000 times fainter 2,000,000 times fainter 100,000,000 times fainter then the Milky Way then the Milky Way then the Milky Way discovered with SDSS discovered with DES Converting observed dwarf numbers into total

• Selection efficiency

• Baryonic disc

• Probabilistic framework

• Flexible dwarf-to-halo mapping Converting observed dwarf numbers into total

Jethwa et al 2017 Converting to WDM constraints Three predictions of ɅCDM

for sub-structure around the Milky Way

1. Hundreds of dwarf galaxy satellites. ✌

2. Most massive dwarfs have satellites of their own

3. Most low-mass sub-halos are forever dark Prediction 2 Most massive dwarfs have satellites of their own

Leo II

Leo I Ursa Minor Sextans Draco

l=180o l=0o, b=0o l=-180o

Sagittarius Carina LMC SMC Classical

Fornax Sculptor

CVn II Com CVn I Boo III Koposov 1 Willman 1 Boo I Leo II UMa I Boo II Leo V Segue 1 Leo I Leo T Ursa Minor Leo IV UMa II Sextans Draco Her Koposov 2 l=180o l=0o, b=0o l=-180o

Sagittarius Segue 3 Carina LMC SMC Segue 2 Classical SDSS Pisces II

Fornax Sculptor

CVn II Com CVn I Boo III Koposov 1 Willman 1 Boo I Leo II UMa I Boo II Leo V Segue 1 Leo I Leo T Ursa Minor Leo IV UMa II Crater Sextans Draco Her Koposov 2 l=180o l=0o, b=0o l=-180o

Sagittarius Segue 3 Carina LMC SMC Segue 2 Classical SDSS Pisces II VST ATLAS Fornax Sculptor

CVn II Com CVn I Boo III Koposov 1 Willman 1 Boo I Leo II UMa I Boo II Leo V Segue 1 Leo I Leo T Ursa Minor Leo IV UMa II Crater Sextans Draco Her Koposov 2 l=180o l=0o, b=0o l=-180o

Sagittarius Segue 3 Carina LMC Ind 1 SMC Segue 2 Pic Tuc 2 Classical Ret 2 SDSS Pisces II Gru Hor Eri 3 Eri 2 VST ATLAS Pho 2 Hor 2 DES Year 1 Fornax Sculptor

CVn II Com CVn I Boo III Koposov 1 Willman 1 Boo I Leo II UMa I Boo II Leo V Segue 1 Leo I Leo T Ursa Minor Leo IV UMa II Crater Sextans Draco Her Koposov 2 l=180o l=0o, b=0o l=-180o

Sagittarius Segue 3 Carina LMC Ind 1 Peg 3 SMC Segue 2 Pic Tuc 2 Classical Ret 2 SDSS Pisces II Gru Hor Eri 3 Eri 2 VST ATLAS Pho 2 Hor 2 DES Year 1 Kim et al Fornax Sculptor

CVn II Com CVn I Boo III Koposov 1 Willman 1 Boo I Leo II UMa I Boo II Leo V Segue 1 Leo I Leo T Ursa Minor Leo IV UMa II Dra 2 Crater Sextans Draco Her Koposov 2 l=180o l=0o, b=0o l=-180o

Sagittarius Segue 3 Lae 3 Sgr 2 Carina Tri 2 LMC Ind 1 Peg 3 SMC Segue 2 Pic Tuc 2 Classical Ret 2 SDSS Pisces II Gru Hor Eri 3 Eri 2 VST ATLAS Pho 2 Hor 2 DES Year 1 Kim et al Fornax PS1 Sculptor

CVn II Com CVn I Boo III Koposov 1 Willman 1 Boo I Leo II UMa I Boo II Leo V Segue 1 Leo I Leo T Ursa Minor Leo IV UMa II Dra 2 Crater Sextans Draco Her Hyd 2 Koposov 2 l=180o l=0o, b=0o l=-180o

Sagittarius Segue 3 Lae 3 Sgr 2 Carina Tri 2 LMC Ind 1 Peg 3 SMC Segue 2 Pic Tuc 2 Classical Ret 2 SDSS Pisces II Gru Hor Eri 3 Eri 2 VST ATLAS Pho 2 Hor 2 DES Year 1 Kim et al Fornax PS1 Sculptor SMASH

CVn II Com CVn I Boo III Koposov 1 Willman 1 Boo I Leo II UMa I Boo II Leo V Segue 1 Leo I Leo T Ursa Minor Leo IV UMa II Dra 2 Crater Sextans Draco Her Hyd 2 Koposov 2 l=180o l=0o, b=0o l=-180o

Sagittarius Segue 3 Lae 3 Sgr 2 Carina Tri 2 LMC Ind 2 Col 1 Ind 1 Peg 3 SMC Segue 2 Pic Gru 2 Tuc 2 Ret 3 Classical Tuc 5 Ret 2 SDSS Pisces II Gru Tuc 4 Hor Tuc 3 Eri 3 Eri 2 VST ATLAS Pho 2 Hor 2 DES Year 1 Kim et al Fornax PS1 Sculptor SMASH Cet 2 DES Year 2 Magellanic origin for DES satellites?

LMC SMC

sky view in “Magellanic” coordinates Probabilistic modelling of the DES satellites Probabilistic modelling of the DES satellites

Most likely LMC satellites

Three predictions of ɅCDM

for sub-structure around the Milky Way

1. Hundreds of dwarf galaxy satellites. ✌

2. Most massive dwarfs have satellites of their own ✌

3. Most low-mass sub-halos are forever dark Prediction 3 Most low-mass sub-halos remain forever dark What is the mass of the most massive dark sub-halo? What is the mass of the most massive dark sub-halo? = what is the lowest mass dwarf galaxy?

107 - 108 M⊙ Jethwa et al 2017 Test for Prediction 3:

detect DM sub-halos with <108 M⊙ via density perturbations in stellar streams Stellar stream formation

higher energy + higher angular momentum

R+dR L2 R

R-dR L1

lower energy + lower angular momentum Examples of stellar streams in the Milky Way SDSS

Field of Streams, Belokurov et al 2006 Examples of stellar streams in the Milky Way

GD1 stream, no known progenitor Grillmair & Dionatos, 2006

Palomar 5 globular cluster tails by Odenkirchen et al 2003 “Velocity kick” controls the stream perturbation

Erkal & Belokurov 2015a DM sub-halo velocity

distance along stream stream velocity kick Dynamics of gap formation Stream gap evolution

Erkal & Belokurov 2015a Detection of two “gaps” in Pal 5 stream

measurements of the stream properties based on the deepest imaging of a stellar stream to date Detection of two “gaps” in Pal 5 stream

measurements of the stream properties based on the deepest imaging of a stellar stream to date

stream density Detection of two “gaps” in Pal 5 stream

Fiducial model

model

Erkal, Koposov & Belokurov 2017 Detection of two “gaps” in Pal 5 stream

Fiducial model

model

Perturbations by subhalos

model

Erkal, Koposov & Belokurov 2017 The End