dark matter and dark energy: gases that dominate the...
TRANSCRIPT
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Dark Matter and Dark Energy:
gases that dominate
the Universe
Dragan Huterer
University of Michigan
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http://hetdex.org/dark_energy/
http://hetdex.org/dark_energy/http://hetdex.org/dark_energy/
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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)
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•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
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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)
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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
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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!)
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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
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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?”
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Dark Matter
Fritz Zwicky
“Dunkle Materie”,1933
Vera Rubin
flat rotation curves, 1970s
Coma cluster
of galaxies
Illustration:
Jessie Muir
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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
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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!
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M. Deliyergiyev, 2016
Worldwide quest to (in)directly detect DM
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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
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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!
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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
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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?)