reionisation: in the context of small-scale structure Sownak Bose - - PowerPoint PPT Presentation

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reionisation: in the context of small-scale structure Sownak Bose - - PowerPoint PPT Presentation

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Durham, UK 01 August, 2019 reionisation: in the context of small-scale structure Sownak Bose sownak.bose@cfa.harvard.edu @Swnk16 Durham, UK 01 August, 2019 reionisation: in the f o the nature of s e t y i context of l a l W

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reionisation: in the context of

Sownak Bose

@Swnk16 sownak.bose@cfa.harvard.edu

01 August, 2019 Durham, UK

small-scale structure

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reionisation: in the context of

Sownak Bose

@Swnk16 sownak.bose@cfa.harvard.edu

01 August, 2019 Durham, UK

t h e s a t e l l i t e s

  • f

t h e M i l k y W a y the nature of dark matter

small-scale structure

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[Image credit: NAOJ / ESO]

a milestone in the history of the cosmos

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the missing satellites “problem”

Aquarius simulation Springel+ (2008)

~ 54 satellites known around MW (SDSS+DES) > 100,000 DM subhaloes predicted by CDM why do most subhaloes remain dark?

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it ain’t easy being a galaxy

absolute magnitude abundance of objects

DM haloes (rescaled by const. M/L)

  • bserved

galaxies AGN feedback SN feedback + photoionisation making a galaxy in a small halo is doubly difficult because: (1) reionisation heats gas above Tvir, preventing cooling, and (2) SN feedback removes SF gas from haloes

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APOSTLE simulations of the Local Group Sawala+ (2016)

feedback + photoionisation + the impact of the central galaxy [see also Rees (1986); Efstathiou (1992); Kauffman+ (1993); Loeb & Barkana (2000); Bullock+ (2001); Benson+ (2002); Brooks & Zolotov (2014); Wetzel+ (2016) etc.]

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APOSTLE simulations of the Local Group Sawala+ (2016)

feedback + photoionisation + the impact of the central galaxy [see also Rees (1986); Efstathiou (1992); Kauffman+ (1993); Loeb & Barkana (2000); Bullock+ (2001); Benson+ (2002); Brooks & Zolotov (2014); Wetzel+ (2016) etc.]

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APOSTLE simulations of the Local Group Sawala+ (2016)

feedback + photoionisation + the impact of the central galaxy [see also Rees (1986); Efstathiou (1992); Kauffman+ (1993); Loeb & Barkana (2000); Bullock+ (2001); Benson+ (2002); Brooks & Zolotov (2014); Wetzel+ (2016) etc.]

“(It makes me) apoplectic! The only example I know where the solution precedes the problem!”

  • Someone in this room
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APOSTLE simulations of the Local Group Sawala+ (2016)

feedback + photoionisation + the impact of the central galaxy [see also Rees (1986); Efstathiou (1992); Kauffman+ (1993); Loeb & Barkana (2000); Bullock+ (2001); Benson+ (2002); Brooks & Zolotov (2014); Wetzel+ (2016) etc.]

“(It makes me) apoplectic! The only example I know where the solution precedes the problem!”

  • Someone in this room

(correct: it was Carlos Frenk)

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zreion = 6 zreion = 10

SB, Deason, Frenk [arXiv: 1802.10096]

fraction of mass formed before z=6 present-day stellar mass [ Mø ]

[see also Wheeler+ 2015; Garrison-Kimmel+ 2019; Munshi+ 2019]

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faint satellites typically assemble bulk of stellar mass prior to reionisation

zreion = 6 zreion = 10

SB, Deason, Frenk [arXiv: 1802.10096]

fraction of mass formed before z=6 present-day stellar mass [ Mø ]

[see also Wheeler+ 2015; Garrison-Kimmel+ 2019; Munshi+ 2019]

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faint satellites typically assemble bulk of stellar mass prior to reionisation bright satellites assemble much later: they know nothing about when reionisation took place!

zreion = 6 zreion = 10

SB, Deason, Frenk [arXiv: 1802.10096]

fraction of mass formed before z=6 present-day stellar mass [ Mø ]

[see also Wheeler+ 2015; Garrison-Kimmel+ 2019; Munshi+ 2019]

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faint satellites typically assemble bulk of stellar mass prior to reionisation bright satellites assemble much later: they know nothing about when reionisation took place! this is what one would expect From the hierarchical growth

  • f structure

zreion = 6 zreion = 10

SB, Deason, Frenk [arXiv: 1802.10096]

fraction of mass formed before z=6 present-day stellar mass [ Mø ]

[see also Wheeler+ 2015; Garrison-Kimmel+ 2019; Munshi+ 2019]

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faint satellites typically assemble bulk of stellar mass prior to reionisation bright satellites assemble much later: they know nothing about when reionisation took place! this is what one would expect From the hierarchical growth

  • f structure

zreion = 6 zreion = 10

SB, Deason, Frenk [arXiv: 1802.10096]

fraction of mass formed before z=6 present-day stellar mass [ Mø ]

[see also Wheeler+ 2015; Garrison-Kimmel+ 2019; Munshi+ 2019]

Brown+ (2014)

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a unique imprint in the lf of satellites

redshift of reionisation filtering scale for reionisation

SB, Deason, Frenk [arXiv: 1802.10096]

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a unique imprint in the lf of satellites

redshift of reionisation filtering scale for reionisation

SB, Deason, Frenk [arXiv: 1802.10096]

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the diversity of ultrafaint abundances

and the diversity of halo growth histories

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numerics

parent N-body simulation: COLOR

Lbox = 100 Mpc; mp = 8.8 × 106 M⊙

High-resolution zoom-in volume: COCO

Lhr = 24 Mpc; mp = 1.6 × 105 M⊙ }

semi-analytic model of galaxy formation: GALFORM [Cole+ 1994, 2000; Lacey+ 2016] [Sawala+ 2016; Hellwing, …, SB+ 2016]

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# UFs relative to the average in mass bin redshift at which 50% of host’s mass was formed

Mhost

200 = [1 − 1.3] × 1012 M⊙

SB, Deason, Belokurov, Frenk [soon, I hope]

roughly equal split 56% above mean 70% above mean

[~ 400 objects]

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# UFs relative to the average in mass bin redshift at which 50% of host’s mass was formed

Mhost

200 = [1 − 1.3] × 1012 M⊙

SB, Deason, Belokurov, Frenk [soon, I hope]

roughly equal split 56% above mean 70% above mean

[~ 400 objects]

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# UFs relative to the average in mass bin redshift at which 50% of host’s mass was formed

Mhost

200 = [1 − 1.3] × 1012 M⊙

  • ur Galaxy’s past history and present-day satellite content are pretty unique

SB, Deason, Belokurov, Frenk [soon, I hope]

roughly equal split 56% above mean 70% above mean an ancient accretion event likely dragged in a large number of UFs

[~ 400 objects]

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where can you find an ultrafaint?

number of satellites stellar mass [ ]

M⊙

  • the ultrafaints are generally

concentrated pretty centrally

  • profiles are more centrally-

concentrated in early-forming haloes

  • a sizeable proportion (~70%) of

these are identified as “orphans” — whose subhaloes have been disrupted below the resolution limit of the simulation [20 particle limit:

]

3.2 × 106 M⊙

SB, Deason, Belokurov, Frenk [soon, I hope]

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what if the dark matter isn’t CDM?

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cold dark matter warm dark matter

Movie: Mark Lovell

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cold dark matter warm dark matter

Movie: Mark Lovell

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halo mass [ ]

M⊙

formation redshift

SB+ (2016) [arXiv: 1507.01998]

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halo mass [ ]

M⊙

formation redshift

below a characteristic scale, halo formation is delayed relative to CDM differences driven by this feature

SB+ (2016) [arXiv: 1507.01998]

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SB+ (2017) [arXiv: 1604.07409]

… and also seen in hydro simulations, Lovell+ (2018)

redshift age of universe [Gyr] specific star formation rate [yr-1] stellar mass assembly up to z = 7

[Mark’s talk from Monday]

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UV luminosity function

high-z galaxies form through mostly monolithic collapse and mergers are more gas-rich than in CDM

absolute UV magnitude

[see also Wang+ (2017)]

SB+ (2017) [arXiv: 1604.07409]

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log [stellar mass/ ]

M⊙

5 7 9 11 5 7 9 11 5 7 9 11 5 7 9 11

redshift

Compensation: The dominant sources of ionising photons tend to be more massive in sterile neutrino cosmologies than in CDM

tracing the sources of ionising photons

SB+ 2016 [arXiv: 1605.03179]

increasingly warm dark matter

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going one step further than averaged quantities

with the topology of reionisation

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CDM, fesc = 0.5 1.5 keV, fesc = 0.5 1.5 keV, fesc = 1.0

self-consistent reionisation simulations with Arepo-RT (Kannan+2018) with IllustrisTNG physics

ionisation history consistent with obs. constraints reionisation way too late reionises before CDM

SB, Kannan, Mason, Vogelsberger+

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CDM, fesc = 0.5 1.5 keV, fesc = 0.5 1.5 keV, fesc = 1.0

self-consistent reionisation simulations with Arepo-RT (Kannan+2018) with IllustrisTNG physics

increasing fesc can reconcile the timing of reionisation, but doesn’t add small-scale “ionising power”

ionisation history consistent with obs. constraints reionisation way too late reionises before CDM

SB, Kannan, Mason, Vogelsberger+

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CDM, fesc = 0.5 1.5 keV, fesc = 0.5 1.5 keV, fesc = 1.0

self-consistent reionisation simulations with Arepo-RT (Kannan+2018) with IllustrisTNG physics

ionisation history consistent with obs. constraints reionisation way too late reionises before CDM

SB, Kannan, Mason, Vogelsberger+

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conclusions

  • ultrafaint galaxies are unique: bearing memory of reionisation, the

assembly of the host galaxy, and the nature of the dark matter

  • at fixed mass, haloes that assemble early contain more UFs — histories

similar to that of our Galaxy are quite rare

  • a large fraction of these satellites are located within the inner ~ 60 kpc
  • f the host halo at z = 0
  • despite the absence of low-mass dwarfs, DM models with a free-

streaming cutoff have no issues reionising in time: brighter galaxies form efficiently, and carry the burden

  • future 21cm experiments may be able to probe the absence of small-

scale structure by measuring the size distribution of ionisation fronts @Swnk16 sownak.bose@cfa.harvard.edu