AST4320 - Cosmology and extragalactic astronomy Lecture 14 The Too - - PowerPoint PPT Presentation

▶
ast4320 cosmology and extragalactic astronomy
SMART_READER_LITE
LIVE PREVIEW

AST4320 - Cosmology and extragalactic astronomy Lecture 14 The Too - - PowerPoint PPT Presentation

Oct 04, 2023 125 likes •637 views

AST4320 - Cosmology and extragalactic astronomy Lecture 14 The Too Big to Fail Problem The Nature of Dark Matter 1 Previously on AST4320: Missing Satellite Problem (see review by Weinberg et al. 2013, arXiv:1306.0913) Left: simulated dark

slide-1
SLIDE 1

Lecture 14 AST4320 - Cosmology and extragalactic astronomy The Too Big to Fail Problem The Nature of Dark Matter

1
slide-2
SLIDE 2

Previously on AST4320: Missing Satellite Problem

(see review by Weinberg et al. 2013, arXiv:1306.0913) 2 Left: simulated dark matter distribution in dark matter halo with M=1012 Msun. Circles denote 9 most massive substructures or `satellites’. Right: Spatial distribution of observed Milky Way `satellites’.
slide-3
SLIDE 3

Observational Constraints on Dark Matter Halo Profiles (see review by W. De Blok, arXiv:0910.3538)

(Oh et al. 2011; THINGS* survey. Colored points are the dwarfs.) (* The HI Nearby Galaxy Survey)
slide-4
SLIDE 4

The Nature of the Dark Matter

4
slide-5
SLIDE 5

The Nature of the Dark Matter

5 What is the dark matter, and why is it `cold’? Cosmic microwave background and observed large-scale structure in the Universe (i.e. clustering of galaxies) provide constraints on content of Universe: Ordinary matter (baryons, leptons, photons) make up ~ 4% of Universal energy density. `Dark energy’ accounts for ~73%. Dark matter accounts for the remaining ~23%. `Just as the chocolate frosting glues the sprinkles together on the cupcake, dark matter binds baryons together to form galaxies, galaxy groups, and galaxy clusters.’
  • A. Peter, 2013, arXiv:1201.3942
slide-6
SLIDE 6 6 What is the dark matter, and why is it `cold’? Dark matter is not:
  • baryonic: evidence from cosmic microwave background, large scale structure, and also
from Big-Bang Nucleosynthesis (maybe more on this in later lecture)

The Nature of the Dark Matter

slide-7
SLIDE 7 7 What is the dark matter, and why is it `cold’? Dark matter is not:
  • baryonic: evidence from cosmic microwave background, large scale structure, and also
from Big-Bang Nucleosynthesis (maybe more on this in later lecture)
  • composed of `light’ (mX < keV) particles. BB.

The Nature of the Dark Matter

slide-8
SLIDE 8 8 What is the dark matter, and why is it `cold’? Dark matter is not:
  • baryonic: evidence from cosmic microwave background, large scale structure, and also
from Big-Bang Nucleosynthesis (maybe more on this in later lecture)
  • composed of `light’, mX < keV, particles. These particles would be `relativistic’ when T
  • f the Universe was ~ 1 keV. This would suppress growth of structure on `small’
scales at levels that are at odds with Lyman alpha forest (next lecture) constraints. This is illustrated on the next slide.

The Nature of the Dark Matter

slide-9
SLIDE 9

Constraints on (Warm) Dark Matter

9 Observational constraints mass power spectrum `primordial’ P(k) `Meszaros’ suppression rH matter-radiation equality T~ eV `rH‘ relativisitic WDM m ~ keV Lyman alpha forest indicates that mDM > keV
slide-10
SLIDE 10

Constraints on other Properties of Dark Matter

10 Constraints on electro-magnetic charge Constraints on self-interaction. `Self-interaction’ refers to interactions among (different species of) dark matter particles, mediated by e.g. `dark gauge bosons’.
slide-11
SLIDE 11

Constraints on other Properties of Dark Matter

11 “Bullet Cluster”: two merging clusters. Pink: hot X-ray emitting gas. Blue: dark matter in the cluster, determined from measuring the lensing signal (lecture~20) from the visible-light images of the galaxies.
slide-12
SLIDE 12

Constraints on other Properties of Dark Matter

12 Constraints on electro-magnetic charge. Constrained by small-scale fluctuations in Cosmic-Microwave Background (see Sigurdson et al. 2004) Constraints on self-interaction. `Self-interaction’ refers to interactions among (different species of) dark matter particles, mediated by e.g. `dark gauge bosons’. Could alter predicted structure of dark matter halos.
slide-13
SLIDE 13

Constraints on other Properties of Dark Matter

13 Constraints on self-interaction. `Self-interaction’ refers to interactions among (different species of) dark matter particles, mediated by e.g. `dark gauge bosons’. Could alter predicted structure of dark matter halos. Example: Recent example of self-interacting dark matter as a solution to the `cusp-core’ problem (with velocity dependent collision cross-section).
slide-14
SLIDE 14

Constraints on other Properties of Dark Matter

14 Density profiles in cosmological simulations that have self-interacting Dark Matter (SIDM). Example of self-interacting dark matter as a solution to the `cusp-core’ problem (with velocity dependent collision cross-section). Slope of density profile flattens from Cusp to Core. Vogelsberger et al. 2012
slide-15
SLIDE 15

Constraints on other Properties of Dark Matter

15 Density profiles in cosmological simulations that have self-interacting Dark Matter (SIDM). SIDM reduces tension between kinematics in observed and simulated satellites. Vogelsberger et al. 2012
slide-16
SLIDE 16

Summary Empirical Constraints Dark Matter

16 Cosmic-Microwave Background limits the charge of the dark matter particle (see Sigurdson et al. 2004) Mass of dark matter particle > keV from Lyman alpha forest observations. Dark matter is at least colder than warm. Collisionless nature of dark matter particle constrained by cluster lensing + X-ray data. Cross-section for `hard-sphere’ elastic scattering though recently some models of self-interacting DM have been put forward that bypass cluster constraints while addressing core-cusp + too big to fail problems in dwarf galaxies
slide-17
SLIDE 17

Some Dark Matter Candidates I: WIMPs

17 WIMP: Weakly Interacting Massive Particles. Popular because:
slide-18
SLIDE 18

Some Dark Matter Candidates I: WIMPs

18 WIMP: Weakly Interacting Massive Particles. Popular because: `Electro-weak’ energy scale at ~200 GeV, above which weak and electromagnetic interaction merges into the `electroweak’ interaction. It is thought that new particles* should exist around this mass-scale. This new particle annihilates into quarks + antiquarks in the early Universe, until density and temperature drops sufficiently that annihilation becomes increasingly rare. The comoving number density nX `freezes’ out. The`predicted’ mass density in this relic density of particles - for the standard assumptions for the mass and annihilation coupling strength - comes out at The fact that particle physics considerations alone, can give the correct order of magnitude for WIMP mass density is referred to as WIMP Miracle. * what these particles are depends on the new physics that is introduced at the electroweak scale. Examples of WIMPS are supersymmetric neutralino, Kaluza-Klein photon,...
slide-19
SLIDE 19

Some Dark Matter Candidates I: WIMPs

19 WIMP: Weakly Interacting Massive Particles. Popular because:
slide-20
SLIDE 20

Some Dark Matter Candidates I: WIMPs

20 WIMP: Weakly Interacting Massive Particles. Popular because:
slide-21
SLIDE 21

Some Dark Matter Candidates II: Other New Particles

21 Other candidates include:
  • Axions: hypothetical particle introduced to resolve the strong CP problem in QCD.
Caution: I know little about this. There are many reviews on dark matter candidates out there (often with the obscure title `Dark Matter’). I followed Peter’s review that has many references in there.
slide-22
SLIDE 22

Some Dark Matter Candidates II: Other New Particles

22 Other candidates include:
  • Axions: hypothetical particle introduced to resolve the strong CP problem in QCD.
  • Gravitinos: supersymmetric partner of graviton. Not as popular as WIMPs because
hard to detect & tuning required to get matter density correct. Caution: I know little about this. There are many reviews on dark matter candidates out there (often with the obscure title `Dark Matter’). I followed Peter’s review that has many references in there.
slide-23
SLIDE 23

Some Dark Matter Candidates II: Other New Particles

23 Other candidates include:
  • Axions: hypothetical particle introduced to resolve the strong CP problem in QCD.
  • Gravitinos: supersymmetric partner of graviton. Not as popular as WIMPs because
hard to detect & tuning required to get matter density correct.
  • Sterile Neutrinos: neutrinos that do not act electroweakly. Introduced to generate
mass for `active’ neutrinos, explain neutrino experiment anomalies,... Caution: I know little about this. There are many reviews on dark matter candidates out there (often with the obscure title `Dark Matter’). I followed Peter’s review that has many references in there.
slide-24
SLIDE 24

Some Dark Matter Candidates II: Other New Particles

24 Other candidates include:
  • Axions: hypothetical particle introduced to resolve the strong CP problem in QCD.
  • Gravitinos: supersymmetric partner of graviton. Not as popular as WIMPs because
hard to detect & tuning required to get matter density correct.
  • Sterile Neutrinos: neutrinos that do not act electroweakly. Introduced to generate
mass for `active’ neutrinos, explain neutrino experiment anomalies,...
  • Hidden sector dark-matter: dark sector may be as rich as ordinary standard model,
but not `communicate’ much at all. These sectors are referred to as `hidden’ sectors, which may contain `dark photons’. Caution: I know little about this. There are many reviews on dark matter candidates out there (often with the obscure title `Dark Matter’). I followed Peter’s review that has many references in there.
slide-25
SLIDE 25

Dark Matter Searches.

25 Searches for dark matter can be done in
  • Colliders: given that dark matter is neutral and weakly interacting, they behave like
giant neutrinos in colliders. Missing energy* in collisions may hint at existence of e.g.
  • WIMPs. So far, no evidence for physics beyond standard model.
Moreover, even if hints for a WIMP are found, it is unclear whether it would be stable
  • ver cosmological times (let go longer than a ns).

HARD

slide-26
SLIDE 26

Dark Matter Searches.

26 Searches for dark matter can be done via
  • Direct detection: looking for the collision of a WIMP with an atomic nucleus in the
  • LAB. Experiments include DAMA/LIBRA, CRESST, CoGeNT, XENON100, CDMS-II,
COUPP .
slide-27
SLIDE 27

Intermezzo: Nuclear Recoil

27 WIMP-Nucleus Interaction: WIMPs have finite cross-section for interacting with standard model particles. Momentum conservation during scattering of WIMPs by atomic nuclei gives rise to `recoil’ of nucleus with E ~few to tens of keV. Nuclear recoil can be manifest through scintillation, collisional ionization Why e.g. Xenon?:
  • 1. transparent to own scintillation flux (no subsequent absorption).
  • 2. liquid xenon is so dense, neutrons cannot enter target (important, as neutron induced
recoils indistinguishable from those by WIMPs).
slide-28
SLIDE 28

Intermezzo: Nuclear Recoil

28 Nuclear recoil can be manifest through scintillation, collisional ionization
slide-29
SLIDE 29

Intermezzo: Nuclear Recoil

29 WIMP-Nucleus Interaction: WIMPs have finite cross-section for interacting with standard model particles. Momentum conservation during scattering of WIMPs by atomic nuclei gives rise to `recoil’ of nucleus with E ~few to tens of keV. Nuclear recoil can be manifest through scintillation, collisional ionization Why e.g. Xenon?:
  • 1. transparent to own scintillation flux (no subsequent absorption).
  • 2. liquid xenon is so dense, neutrons cannot enter target (important, as neutron induced
recoils indistinguishable from those by WIMPs).
slide-30
SLIDE 30

Dark Matter Searches.

30 Searches for dark matter can be done via
  • Direct detection: looking for the collision of a WIMP with an atomic nucleus in the
  • LAB. Experiments include DAMA/LIBRA, CRESST, CoGeNT, XENON100, CDMS-II,
COUPP . A claimed detection by the DAMA Experiment. DAMA looked for annular modulations in their nuclear recoils. As the earth moves around the sun at ~30 km/s, and the sun moves through the dark matter halo at ~ 220 km/s, we expect the dark matter flux to undergo an annual modulation.
slide-31
SLIDE 31

Dark Matter Searches.

31 Searches for dark matter can be done via
  • Direct detection: looking for the collision of a WIMP with an atomic nucleus in the
  • LAB. Experiments include DAMA/LIBRA, CRESST, CoGeNT, XENON100, CDMS-II,
COUPP .
slide-32
SLIDE 32

Dark Matter Searches.

32 Searches for dark matter can be done via
  • Direct detection: looking for the collision of a WIMP with an atomic nucleus in the
  • LAB. Experiments include DAMA/LIBRA, CRESST, CoGeNT, XENON100, CDMS-II,
COUPP . Detection corresponds to WIMP Mass of ~ 10 GeV, and sigma ~ 1e-40 cm^2. Recall:
slide-33
SLIDE 33

Dark Matter Searches.

33 Searches for dark matter can be done via
  • Direct detection: looking for the collision of a WIMP with an atomic nucleus in the
  • LAB. Experiments include DAMA/LIBRA, CRESST, CoGeNT, XENON100, CDMS-II,
COUPP . Summary of constraints on WIMPS by different experiments.
slide-34
SLIDE 34

Dark Matter Searches.

34 Searches for dark matter can be done via
  • Direct detection: looking for the collision of a WIMP with an atomic nucleus in the
  • LAB. Experiments include DAMA/LIBRA, CRESST, CoGeNT, XENON100, CDMS-II,
COUPP . Claimed detection by the DAMA Experiment inconsistent with upper limits by other experiments!
slide-35
SLIDE 35

Dark Matter Searches.

35 Searches for dark matter can be done via
  • Looking for Dark Matter Annhilation: WIMP annihilation in dark matter dense
  • bjects, since annihilation rate increase as (density)2. Good places include:
★ galaxy clusters ★ milky way dwarf galaxies ★ milky way halo ★ center of sun
  • WIMPs annihilate into variety of standard model particles incl. neutrinos, and gamma-
ray photons. WIMP searches have been performed with ★ gamma-ray telescopes such as Fermi & H.E.S.S. ★ neutrino telescopes (sun) Bonus: `WIMP miracle’ provides us with annihilation rate, no free parameters!
slide-36
SLIDE 36

Dark Matter Searches.

36 Searches for dark matter can be done via
  • Looking for Dark Matter Annhilation: H.E.S.S result from last year
No detection.....
slide-37
SLIDE 37

Dark Matter Detections?

37 Unidentified line at E=3.5 keV, associated with decaying dark matter? If so, we should see it in the Milky Way (?) Which we do not. Very hot topic. Recent (Feb 2014) X-ray observations of nearby galaxy clusters.
slide-38
SLIDE 38

Dark Matter Detections?

38 Unidentified line at E=3.5 keV, associated with decaying dark matter? If so, we should see it in the Milky Way (?) Which we do not. Very hot topic. Recent (Feb 2014) X-ray observations of nearby galaxy clusters.
slide-39
SLIDE 39

Dark Matter Detections?

39 Recent (Feb 2014) X-ray observations of nearby galaxy clusters.
slide-40
SLIDE 40

Dark Matter Detections?

40 Recent (Feb 2014) X-ray observations of nearby galaxy clusters.
slide-41
SLIDE 41

Dark Matter Detections?

41 Recent (Feb 2014) X-ray observations of nearby galaxy clusters.
slide-42
SLIDE 42 42

Dark Matter Detections?

Fermi Gamma Ray observations of the full sky. A diffuse gamma-ray glow - centered on Milky Way center - has been observed. This so-called `Fermi-haze’ has been speculated to be a dark matter signal.
slide-43
SLIDE 43

`Macro Dark Matter’

43 Massive `non-particle’ dark matter particles (see arxiv:1410.2236). Motivation: reaction rate between baryons and dark matter particles is ~ Moreover,

}

Dark matter is `dark’ because it barely interacts with ordinary matter, i.e. GammaXb is low Traditionally, a low is associated with a low Alternatively, a low is associated with a high MX High can be macroscopically high 1e-12-1e34 gr! `Macro dark matter’
slide-44
SLIDE 44

`Macro Dark Matter’ (journal club, yesterday)

44 Weird non-particle dark matter particles (see arxiv:1410.2236):
  • nuclearites
  • strangelets
  • strange baryon Q-balls
  • baryonic colour superconductors
  • compact composite objects
  • compact ultradense objects
  • primordial black holes
  • cheese
  • ...
`Macro dark matter’ (Macros) Pretty amazing world of possibilities.
slide-45
SLIDE 45

Summary Knowledge on Dark Matter

45 Mass of dark matter particle > keV from Lyman alpha forest observations. Dark matter is at least colder than warm. Collisionless nature of dark matter particle constrained by cluster lensing + X-ray data. Cross-section for `hard-sphere’ elastic scattering though recently some models of self-interacting DM have been put forward that bypass cluster constraints while addressing core-cusp + too big to fail problems in dwarf galaxies Theoretically, the leading popular candidate is the WIMP . Universal mass density in WIMPs ~ dark matter density (`WIMP’ miracle). Observational constraints on WIMPs, are improving. However, stage is wide-open. Many other candidates including axions, hidden sector dark matter, macro dark matter,...
slide-46
SLIDE 46

Outlook

46 Next lecture: turn to the `bright’ side of extragalactic astrophysics. Focus on Lyman alpha forest:
  • provide constraints on mass power spectrum on smallest scales (and hence dark
matter properties)
  • provides insights into distribution & properties of gas in range of densities from linear
regime to highly overdense gas in outskirts of galaxies.
slide-47
SLIDE 47

`Too Big To Fail’ Problem.

Boylan-Kolchin et al. 2011/2012 Satellite Luminosity function
  • bserved
simulated
slide-48
SLIDE 48

Constraints on (Warm) Dark Matter

Observational constraints mass power spectrum `primordial’ P(k) `Meszaros’ suppression rH matter-radiation equality T~ eV `rH‘ relativisitic WDM m ~ keV Lyman alpha forest indicates that mDM > keV
slide-49
SLIDE 49

Constraints on other Properties of Dark Matter

“Bullet Cluster”: two merging clusters. Pink: hot X-ray emitting gas. Blue: dark matter in the cluster, determined from measuring the lensing signal (lecture~20) from the visible-light images of the galaxies.