DETECTIONS
of
WIMP SIGNATURES
via
COSMIC SHEAR – GAMMA RAY
TOMOGRAPHY
Stefano Camera
Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
THEWIMPQUEST
•
Strong observational evidence for dark matter (DM)
•
Best DM candidate represented by weakly interacting massive
particles (WIMPs)—e.g. those predicted by many extensions of the
Standard Model of Particle Physics
[Jungman, Kamionkowski & Griest (1996), Phys. Rept. 267, 195]
[Fornengo (2008), Adv. Space Res. 41, 2010]
•
Strong experimental effort towards the detection of a WIMP DM
signal—both by direct and indirect detections
[Feng (2010), Ann. Rev. Astron. Astrophys. 48, 495]
1 yet unsuccessful!
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
WIMPIMPRINTSINGAMMARAYS?
•
According to the WIMP paradigm, DM particle annihilation or
decay can produce monochromatic gamma-ray lines and
contribute to the diffuse gamma-ray background
•
Unresolved astrophysical sources like blazars, star forming galaxies
(SFGs) or misaligned AGNs also contribute to the extragalactic
gamma-ray background—albeit the exact amount of their
contribution is still unknown
•
Since the energy spectrum of the gamma-ray background is
compatible with a power-law—without evident spectral features—
it seems as though DM cannot play a leading rôle in the whole
energy range
[Abdo et al. (2010), Phys. Rev. Lett. 104, 101101;
Ackermann et al. (2012), Phys. Rev. D86, 022002]
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
WIMPIMPRINTSINGAMMARAYS?
•
Gamma-ray energy spectrum
[SC et al. (2013), Astrophys. J. 771, L5]
1 Motivations for cross-correlating with cosmic shear from M. Fornasa’s and M. Regis’ talks
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
WIMPIMPRINTSINGAMMARAYS?
•
Gamma-ray anisotropy auto-correlation angular power spectrum
[SC et al. (2013), Astrophys. J. 771, L5]
1 Motivations for cross-correlating with cosmic shear from M. Fornasa’s and M. Regis’ talks
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
WEAKGRAVITATIONALLENSING
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
WEAKGRAVITATIONALLENSING
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
WEAKGRAVITATIONALLENSING
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
WEAKGRAVITATIONALLENSING
<0>0
<0>0
κ
�[γ]
<0>0
κ
κ
�[γ]
�[γ]
�[γ]
κ
�[γ]
�[γ]
�[γ]
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
COSMICSHEAR&GAMMARAYS
•
Gamma-ray – cosmic-shear cross-corr. angular power spectrum
C�γκ =
�
�
�
dz W (z)W (z) s
�
P k=
,z
2
H(z)
χ (z)
χ(z)
γ
κ
•
The window functions, WX(z), encode the relative magnitude of the signals
and the overlap in the observed redshift range
•
The source power spectrum, P s(k, z), represents the three-dimensional
correlation between the large-scale gravitational potential—the lensing
source field—and the processes at the origin of astrophysical and WIMPsourced gamma rays
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
COSMICSHEAR&GAMMARAYS
•
Photometric redshift survey
•
Gamma-ray telescope
•
redshift range 0.3 < z < 1.5
•
energy range 1 < E/GeV < 300
•
sky coverage 5,000 sq. deg.
•
all sky
•
~13.3 galaxies per sq. arcmin
•
~0.27º beam size
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
COSMICSHEAR&GAMMARAYS
•
Gamma-ray – cosmic-shear cross-corr. angular power spectrum
[SC et al. (2013), Astrophys. J. 771, L5]
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
COSMICSHEAR&GAMMARAYS
•
•
Photometric redshift survey
Y
Gamma-ray telescope
P
H
A
•
energy range 1 < E/GeV < 300
•
all sky
~13.3
Tgalaxies per sq. arcmin
•
~0.27º beam size
3 redshift bins of width
∆z = 0.4 in the observed range
0.3 < z < 1.5
•
6 energy bins between 1 – 2,
2 – 5, 5 – 10, 10 – 20, 20 – 50,
50 – 100 and 100 – 300 GeV
•
redshift range 0.3 < z < 1.5
•
sky coverage 5,000 sq. O
deg.
•
•
O
G
M
R
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
FORECASTSFROMTOMOGRAPHY
•
In the Bayesian approach, and under the assumption of Gaussian
likelihoods, the Fisher information matrix approximates the
inverse of the covariance matrix of a given model parameters
[Fisher (1935), J. R. Stat. Soc. 98, 39;
Tegmark, Taylor & Heavens (2007), Astrophys. J. 480, 22]
F=
Fγκ
αβ =
�
�
(2� +
�
∂ ln L
−
∂ϑ2
2
�
γκ
γκ −1 ∂C�
(Γ� )
1)fsky
∂ϑα
∂ϑβ
γκ
∂C�
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
FORECASTSFROMTOMOGRAPHY
•
Given a future experiment, via its Fisher matrix we can
•
Infer accuracy on parameters measurements
σ (ϑα ) =
(F−1 )αα
Forecast error confidence regions
Parameter 2
•
�
Parameter 1
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
FORECASTSFROMTOMOGRAPHY
•
•
_
Benchmark DM model (dominant final state bb):
•
•
Decaying DM: mass 200 GeV, decay rate 3.3 × 10–27 s–1
Annihilating DM: mass 100 GeV, annihilation rate 8 × 10–26 cm3 s–1
Astrophysical sources: SFGs and Blazars
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
FORECASTSFROMTOMOGRAPHY
•
•
_
Benchmark DM model (dominant final state bb):
•
•
Decaying DM: mass 200 GeV, decay rate 3.3 × 10–27 s–1
Annihilating DM: mass 100 GeV, annihilation rate 8 × 10–26 cm3 s–1
Astrophysical sources: SFGs and Blazars
P
R
E
L
I
M
I
N
A
R
Y
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
FORECASTSFROMTOMOGRAPHY
•
•
_
Benchmark DM model (dominant final state bb):
•
•
Decaying DM: mass 200 GeV, decay rate 3.3 × 10–27 s–1
Annihilating DM: mass 100 GeV, annihilation rate 8 × 10–26 cm3 s–1
Astrophysical sources: SFGs and blazars
P
R
E
L
I
M
I
N
A
R
Y
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
TAKEHOMEMESSAGE
•
Albeit WIMP DM is currently an (almost) established ingredient
of our understanding of the Universe, we have so far failed to
detect it—with noticeable though controversial exceptions
•
The diffuse gamma-ray background does not, in itself, provide an
exploitable tool for probing WIMP DM through its annihilating/
decaying processes, because astrophysical emission is far dominant
•
Contrarily, the cross-correlation of extragalactic gamma-ray
background anisotropies with cosmic shear appears promising!
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
TAKEHOMEMESSAGE
•
Contrarily, the cross-correlation of extragalactic gamma-ray
background anisotropies with cosmic shear appears promising!
•
Cosmic shear window function nicely overlaps with that of ann./dec. DM,
whilst this happens only at intermediate or high redshift for SFGs or blazars
•
Since both the shear and WIMP-induced gamma-ray signals are stronger for
larger haloes, their cross-correlation is more effective compared to that of
astrophysical sources
•
The combination of Fermi with cosmic shear surveys like DES, and the
exploitation of energy and redshift tomography, can thus potentially provide
evidence for WIMPs
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
THANKYOU!
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
WIMPIMPRINTSINGAMMARAYS?
•
•
_
Benchmark DM model (dominant final state bb):
•
Annihilating DM
mass 100 GeV
ann. rate 8×10–26 cm3/s
•
Decaying DM
mass 200 GeV
dec. rate 3×1026 s
[SC et al. (2013), Astrophys. J. 771, L5]
Astrophysical sources:
•
•
SFGs
Blazars
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
WIMPIMPRINTSINGAMMARAYS?
Astrophysical sources:
SFGs
Ferm
-6
10
SFG
tota
l
i dat
a
astro
-7
10
c.
de
DM
mAG
N
blazars
-8
10
ann.
Blazars
DM
•
•
10
-1
•
Decaying DM
mass 200 GeV
dec. rate 3×1026 s
[SC et al. (2013, in prep.)]
-5
-2 -1
Annihilating DM
mass 100 GeV
ann. rate 8×10–26 cm3/s
2
•
•
E I [GeV cm s sr ]
•
_
Benchmark DM model (dominant final state bb):
-9
10
1
10
100
E [GeV]
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
WIMPIMPRINTSINGAMMARAYS?
•
•
_
Benchmark DM model (dominant final state bb):
•
Annihilating DM
mass 100 GeV
ann. rate 8×10–26 cm3/s
•
Decaying DM
mass 200 GeV
dec. rate 3×1026 s
[SC et al. (2013), Astrophys. J. 771, L5]
Astrophysical sources:
•
•
SFGs
Blazars
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
COSMICSHEAR&GAMMARAYS
•
Both cosmic shear and cosmological gamma-ray emission stem
from the presence of DM in the Universe:
•
•
DM structures are responsible for bending the light via gravitational lensing
Those same objects can emit gamma-rays, either because they host
astrophysical sources or directly by WIMP DM annihilations or decays
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
COSMICSHEAR&GAMMARAYS
•
Cross-correlation angular power spectrum of anisotropies in the
extragalactic gamma-ray background and cosmic shear
C�γκ =
�
�
�
dz W (z)W (z) s
�
P k=
,z
2
H(z)
χ (z)
χ(z)
γ
κ
•
The window functions, WX(z), encode the relative magnitude of the signals
and the overlap in the observed redshift range
•
The source power spectrum, P s(k, z), represents the three-dimensional
correlation between the large-scale gravitational potential—the lensing
source field—and the processes at the origin of astrophysical and WIMPsourced gamma rays
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
COSMICSHEAR&GAMMARAYS
-1
W / < IEGB > [Mpc ]
•
-3
10
Window
functions
Window
functions
•
dec.
Cosmic
DM shear: Poisson’s eq., galaxy redshift distribution and background
geometry
-4
10
•
•
SFG
mAGN
DM:
dec./ann. properties of the WIMP DM candidate
shear
ann. DM
-5
10
Astrophysical sources: bulk of unresolved sources depending upon Fermi
DE
gamma-ray threshold
S
-6
10
ars
cli
Eu
blaz
d
-7
10
0
1
2
redshift z
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
COSMICSHEAR&GAMMARAYS
•
3D source power spectra (halo-model approach)
•
•
•
•
Cosmic shear: density contrast
Decaying DM: DM density
Annihilating DM: DM density squared
Astrophysical sources: gamma-ray luminosity functions
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013
DETECTIONSCOSMOLOGY
•
Instituto Superior Técnico, Universidade de Lisboa, Lisboa,
Portugal
S. Camera – Detections of WIMP Signatures via Cosmic Shear - Gamma Ray Tomography @ Anisotropic Universe – Amsterdam, 27th September 2013