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 R L2 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.