Dark Matter and Dark Energy:

gases that dominate

the Universe

Dragan Huterer

University of Michigan

http://hetdex.org/dark_energy/

http://hetdex.org/dark_energy/http://hetdex.org/dark_energy/

Edwin Hubble and the

Expansion of the Universe

(1929)

In 1929 Hubble measured the red

shift (or, redshift) of nearby

galaxies and found that they nearly

all move away from us ⇒

The Universe is Expanding!

100 inch Hooker telescope

(Mt Wilson, CA)

•Velocity is easy: from the Doppler recession of galaxy spectra (first done by astronomer Vesto Slipher, whom Hubble never credited)

•Distance is hard: from Cepheid variable stars

Baking the raisin bread: the farther two raisins are, the faster they are

receding

Expanding spaces: bread & universe

Redshift: shift of galaxy light wavelength (due to galaxy’s motion relative to us)

Light from almost all galaxies is redshifted (and not blueshifted)- the galaxies are receding away from us!

larger wavelength

observed (receding)

smaller wavelength

observed (approaching)

http://hyperphysics.phy-astr.gsu.edu/

Cepheids

(variable stars)

• Empirical finding: Cepheids’ period of pulsation is proportional to intrinsic luminosity

• Measure period

• Measure apparent luminosity (or, flux)

• Then, can get distance:

f = L / (4πd2) (f = flux

L = luminosity)

How do you get distances to galaxies?

http://hyperphysics.phy-astr.gsu.edu/Hbase/astro/cepheid.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/astro/cepheid.html

The original Hubble diagram (1929)

H0 ≈ 70 km/sec/megaparsec

Slope of this relation (velocity vs. distance) is called the Hubble constant H0.

Modern value:

distance

velo

city

(will return to H0 later!)

Three key questions

in cosmology

InflationDark

Matter

Dark

Energy

Cosmological components as fluids

Pressure p, energy density !

The continuity equation is

with

ρ̇+ 3H(p+ ρ) = 0

AAACBXicdZDLSgMxFIYzXmu9VV3qIliESqEktdh2IRTddFnBXqAzlEyatqGZC0lGKEM3bnwVNy4Uces7uPNtzLQVVPRA4OP/z0lyfjcUXGmEPqyl5ZXVtfXURnpza3tnN7O331JBJClr0kAEsuMSxQT3WVNzLVgnlIx4rmBtd3yV+O1bJhUP/Bs9CZnjkaHPB5wSbaRe5sjuB9qWowDm4Vk9F+YTPoUXENl2upfJogJCCGMME8Dlc2SgWq0UcQXixDKVBYtq9DLv5joaeczXVBCluhiF2omJ1JwKNk3bkWIhoWMyZF2DPvGYcuLZFlN4YpQ+HATSHF/Dmfp9IiaeUhPPNZ0e0SP120vEv7xupAcVJ+Z+GGnm0/lDg0hAHcAkEtjnklEtJgYIldz8FdIRkYRqE1wSwtem8H9oFQu4VKhel7K1y0UcKXAIjkEOYFAGNVAHDdAEFNyBB/AEnq1769F6sV7nrUvWYuYA/Cjr7RPCXZYz

d ln ρ

d ln a+ 3(1 + w) = 0

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

H ≡ ȧ/a

AAAB+XicdVDLSgMxFM34rPU16tJNsAiualKKbXdFN11WsA9oh5JJM21oJjMmmUIZ+iduXCji1j9x59+YaSuo6IHA4Zx7uDfHjwXXBqEPZ219Y3NrO7eT393bPzh0j47bOkoUZS0aiUh1faKZ4JK1DDeCdWPFSOgL1vEnN5nfmTKleSTvzCxmXkhGkgecEmOlges2+uw+4dP+MDIpmV+SgVtARYQQxhhmBFeukCW1WrWEqxBnlkUBrNAcuO82S5OQSUMF0bqHUWy8lCjDqWDzfD/RLCZ0QkasZ6kkIdNeurh8Ds+tMoRBpOyTBi7U74mUhFrPQt9OhsSM9W8vE//yeokJql7KZZwYJulyUZAIaCKY1QCHXDFqxMwSQhW3t0I6JopQY8vK2xK+fgr/J+1SEZeLtdtyoX69qiMHTsEZuAAYVEAdNEATtAAFU/AAnsCzkzqPzovzuhxdc1aZE/ADztsn8/OT5w==

the Hubble parameter and a is scale factor

or:

Solutions for w = const:

with eq. of state w = p/ρ

AAAB73icdVBNSwMxEM3Wr1q/qh69BIvgqSal2PYgFL14rGBtoV1KNs22odlkTbJKKf0TXjwo4tW/481/Y7atoKIPBh7vzTAzL4gFNxahDy+ztLyyupZdz21sbm3v5Hf3boxKNGVNqoTS7YAYJrhkTcutYO1YMxIFgrWC0UXqt+6YNlzJazuOmR+RgeQhp8Q6qX1/Fp909VD18gVURAhhjGFKcOUUOVKrVUu4CnFqORTAAo1e/r3bVzSJmLRUEGM6GMXWnxBtORVsmusmhsWEjsiAdRyVJGLGn8zuncIjp/RhqLQraeFM/T4xIZEx4yhwnRGxQ/PbS8W/vE5iw6o/4TJOLJN0vihMBLQKps/DPteMWjF2hFDN3a2QDokm1LqIci6Er0/h/+SmVMTlYu2qXKifL+LIggNwCI4BBhVQB5egAZqAAgEewBN49m69R+/Fe523ZrzFzD74Ae/tEw3KkAQ=

ρ(a) ∝ a−3 (w = 0; matter)

ρ(a) ∝ a−4 (w = +1/3; radiation)

ρ(a) ∝ const (w = −1; vacuum energy)

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

Matter

Vacuum energy

NowCMBNucleosynthesisInflation

Energy/volume

Time>1

00

ord

ers

of

ma

gn

itu

de

How components scale with time

10-35 sec 1 minute 380,000 yr 13.7 Gyr

Radiation a is scale factor a=0: Big Bang

a=1: today

a ≡ 1/(1+z)

ρmat(a) ∝ a−3

ρrad(a) ∝ a−4

ρvac(a) ∝ a0

AAACT3icdVHJTsMwFHTKXrYCRy4WFQgOVAmUpbcKLhxBogWpCdWL41CrThzZDlIV9Q+5wI3f4MIBhHBLWMryJEujmbGeZ+wnnClt2w9WYWx8YnJqeqY4Oze/sFhaWm4qkUpCG0RwIS99UJSzmDY005xeJpJC5HN64XePB/rFDZWKifhc9xLqRXAds5AR0IZql0JXdkQ7c2WEI9D9TdjCG24iRaIFhqtse7fvusUvj4Tgt6c66rkB8tNjt0tlu7JnO7V9B9sVezj4k3FypozyOW2X7t1AkDSisSYclGo5dqK9DKRmhNN+0U0VTYB04Zq2DIwhosrLhn308bphAhwKaU6s8ZD9fiODSKle5BunCd1RP7UB+ZfWSnV46GUsTlJNY/K+KEw5NiEH5eKASUo07xkARDLzVkw6IIFo8wVFU8JHUvw/aO5UnGqldlYt14/yOqbRKlpDm8hBB6iOTtApaiCCbtEjekYv1p31ZL0WcmvBysEKGpnCzBuvQbKD

4%

22%

74%

Makeup of universe today

Dark Matter(suspected since 1930sestablished since 1970s)

Dark Energy(suspected since 1980sestablished since 1998)

Also: radiation (0.01%)

Baryonic Matter(stars 0.4%, gas 3.6%)

Three big questions in cosmology

Dark

Matter

Inflation

(Early Univ)

Dark

Energy

What is the DM

particle?

What are its

interactions,

decay modes..?

What is the

physics behind

the accelerated

expansion?

At what energy?

How many

fields?

With what

interactions?

“Who is this

inflaton field?”

Dark Matter

Fritz Zwicky

“Dunkle Materie”,1933

Vera Rubin

flat rotation curves, 1970s

Coma cluster

of galaxies

Illustration:

Jessie Muir

X-ray light mass (does the lensing)

Modern evidence for Dark Matter

Bullet cluster

Mass profile around a galaxy cluster

Grillo et al 2015

(CLASH team)

Mass

surface

density

Markevitch et al

Clowe et al

Strongest evidence for Dark Matter

Ωdark matterh2= 0.1193± 0.0014

Ωbaryons h2 = 0.0222 ± 0.0001

Planck full-sky map

Planck 2015

cosmic microwave background (CMB)

anisotropy sky map

its angular power spectrum

baryons ≠ dark matter

at ~50 sigma!

M. Deliyergiyev, 2016

Worldwide quest to (in)directly detect DM

1 10 100 1000 10410!50

10!49

10!48

10!47

10!46

10!45

10!44

10!43

10!42

10!41

10!40

10!39

10!38

10!37

10!14

10!13

10!12

10!11

10!10

10!9

10!8

10!7

10!6

10!5

10!4

10!3

10!2

10!1

WIMP Mass !GeV"c2#

WIMP!nucleoncrosssection!cm2#

WIMP!nucleoncrosssection!pb#

CDMS II G

e (2009)

Xenon100

(2012)

CRESST

CoGeNT(2012)

CDMS Si(2013)

EDELWEISS (

2011)

DAMA SIMPLE (2

012)

ZEPLIN-III

(2012)COU

PP (2012)

LUX (2013

)

DA

MIC (2012)

CD

MS

lite (2

013)

DarkSide G

2

PIC

O250-C

3F

8

DarkSide 50

Xenon1T

DEAP3600

LZPICO

250-CF3I

LUX 300d

ay

SuperCDM

S SNOLAB

Sup

erCDMS S NOLAB

8BNeutrinos

Atmospher

ic and DSN

B Neutrinos

7BeNeutrinos

COHERENT N

EUTRIN O SCATTERIN

G

C

OH

ER

EN

T N

EU

TRI NO SCATT

ERING

COHE

RENT N

EUTRINO

SCATT

ERING

J. Cooley, arXiv:1410.4960

Direct searches:

Cross-section vs mass constraints

No direct detection yet!!

• …),

•

•

•

Indirect detection

p

e+

_

The Milky Way in gamma-rays as measured by Fermi-LAT

Numerous alarms about “bumps” in spectra seen from Galaxy,

and from dwarf galaxies (Reticulum, etc)

So far, none are convincing or truly statistically significant

Exciting and fast-developing field, but will be hard to have a

convincing detection of DM just from indirect detection

Three big questions in cosmology

Dark

Matter

Inflation

(Early Univ)

Dark

Energy

What is the

physics behind

the accelerated

expansion?

SNe Ia are “Standard Candles”

If you know the

intrinsic brightness

of the headlights,

you can estimate

how far away the

car is

(car headlights example)

A way to measure (relative) distances to objects far away

But how do you find SNe?

Rate: 1 SN per galaxy per 500 yrs!

Solution:

1. use world’s large telescopes,

2. schedule them to find, then “follow-up” SNe

3. put in heroic hard work

Motivation: to measure geometry of the universe

2011 Physics Nobel Prize (Perlmutter, Riess, Schmidt)

Evidence for Dark energy

from type Ia Supernovae

0 0.5 1Redshift z

-0.5

0

0.5

1

∆ (

m-M

)

SNBAO

always accelerates

accelerates nowdecelerated in the past

always decelerates

flatopen

closed

Huterer & Shafer, Rep. Prog. Phys.; arXiv:1709.01091

0.0 0.5 1.0

0.0

0.5

1.0

1.5

FlatBAO

CMB

SNe

Supernova Cosmology Project

Kowalski, et al., Ap.J. (2008)

m

Union 08SN Ia

compilation

Constraints on dark energy

ρDE / ρcritical

ρmatter / ρcritical

Diverse

methods

agree!

4%

22%

74%

Makeup of universe today

Dark Matter(suspected since 1930sestablished since 1970s)

Dark Energy(suspected since 1980sestablished since 1998)

Also: radiation (0.01%)

Baryonic Matter(stars 0.4%, gas 3.6%)

Huterer & Shafer, Rep. Prog. Phys.; arXiv:1709.01091

Ωm = 1− ΩDE

ΩDE ≡ρDE

ρcrit

w ≡pDE

ρDE

Fine Tuning Problem:

“Why so small”?

Vacuum Energy: Quantum Field Theory

predicts it to be determined by cutoff scale

60-120 orders of magnitude smaller than expected!

Planck scale:

SUSY scale:

(1019 GeV)4(1 TeV)4 }(10−3eV)4Measured:

ρVAC =1

2

�

fields

gi

⇥

∞

0

⇤

k2 + m2d3k

(2π)3�

�

fields

gik4max

16π2

Matter

Dark Energy

NowCMBNucleosynthesisInflation

Energy/volume

Time

>1

00

ord

ers

of

ma

gn

itu

de

10-35 sec 1 minute 380,000 yr 13.7 Gyr

Radiation

The coincidence problem

Time after Big Bang:

V

φ

Lots of theoretical ideas, few compelling ones:

Very difficult to motivate DE naturally

E.g. ‘quintessence’

(evolving scalar field)

mφ ≃ H0 ≃ 10−33 eV

φ̈+ 3Hφ̇+dV

dφ= 0

String landscape?

0 10−120 MPL4 MPL4 ρΛ

Among the ∼10500 minima,

we live in one that allows structure/galaxies to form(selection effect) (anthropic principle)

Pam Jeffries

Kolb & Turner, “Early Universe”, footnote on p. 269:

“It is not clear to one of the authors how a concept as lame

as the “anthropic idea” was ever elevated to the status of a principle”

Landscape

“predicts” the

observed ΩDE

A difficulty: DE theory target accuracy, in e.g. w=p/ρ,

not known a priori

(Δm2)sol ≃ 8×10−5 eV2

(Δm2)atm ≃ 3×10−3 eV2

Contrast this situation with:

1. Neutrino masses:

∑mi = 0.06 eV* (normal)}∑mi = 0.11 eV* (inverted)

*(assuming m3=0)

vs.

2. Higgs Boson mass (before LHC 2012):

mH ≲ O(200) GeV(assuming Standard Model Higgs)

•Ground photometric: ‣Kilo-Degree Survey (KiDS)

‣Dark Energy Survey (DES)

‣Hyper Supreme Cam (HSC)

‣Large Synoptic Survey Telescope (LSST)

•Ground spectroscopic: ‣Hobby Eberly Telescope DE Experiment (HETDEX)

‣Prime Focus Spectrograph (PFS)

‣Dark Energy Spectroscopic Instrument (DESI)

•Space: ‣Euclid

‣Wide Field InfraRed Space Telescope (WFIRST)

Ongoing or upcoming DE experiments:

Dark Energy Survey

• New camera on 4m telescope in Chile

• Observations 2013-2019

• ~700 scientists worldwide

• Analyses in progress (first major results Aug 2017)

Dark Energy Survey (DES)

Cerro Tololo, ChileBlanco

Telescope

0�+10�+20�+30�+40�+50�+60�+70� +340�+350�

−50�

−40�

−30�

κE; 0.2 < z < 1.3

−3

−2

−1

0

1

2

3

S/N

0�+10�+20�+30�+40�+50�+60�+70� +340�+350�

0.24 0.30 0.36 0.42

Ωm

0.72

0.78

0.84

0.90

0.96

S8

DES Y1Planck

DES Y1 + Planck

101

102

0.0

2.0 11

101

102

0.0

2.0 21

101

102

22

101

102

0.0

2.031

101

102

32

101

102

33

101

102

θ (arcmin)

0.0

5.0 41

101

102

θ

42

101

102

θ

43

101

102

θ

44

DES Y1 fiducial

best-fit model

scale cuts

θξ +

(10−

4arcm

in)

DES Year-1 results (August 2017)1350 sq. deg., 35 million galaxies, “double pipeline” for everything

Abbott et al, arXiv:1708.01530

Year-3 data coming out “any month now”, 3x area (close to

5000 sqdeg), 200-300 million galaxies, leading galaxy survey

Brea

king

news

: Hubble tension!

Type Ia supernovae + Cepheid distances give

H0 = 74.0 ± 1.4 (km/s/Mpc)

Cosmic Microwave Anisotropies give

H0 = 67.4 ± 0.4 (km/s/Mpc)

These two measurements are discrepant at about five sigma!*

* once strong-lensing constraints are added, which come out high (H0 ~ 73)

Verde, Treu & Riess arXiv:1907.10625

•Currently the most

exciting thing in field

of cosmology

•Difference between

early- and late-

universe meas. (?)

•Many hundreds of

papers on topic, no

compelling solution

•Weird systematics?

New properties of DM

or DE? ….

Hubble tension!

Conclusions

•Huge variety of new observations in cosmology,

particularly in the large-scale structure

•3 big questions: dark matter, dark energy, inflation

•The current Hubble tension may be a signature of

such a “bump”

•Like particle physicists, we would really like to

see some “bumps” in the data - signatures of new

physics

•Tremendous successes (DM, DE, inflation “proven”),

yet challenges (what is the physics behind them?)