from Dark Matter Annihilation into e - -e + Pairs Maneenate - - PowerPoint PPT Presentation
Multi-Messenger Constraints and Pressure from Dark Matter Annihilation into e - -e + Pairs Maneenate Wechakama Kasetsart University, Thailand M. Wechakama 1 Outline Introduction to Dark Matter (DM) The e - and e + excess in the solar
Kasetsart University, Thailand
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Image credit: http://cdms.phy.queensu.ca/Public_Docs/DM_Intro.html
Rotation curves of galaxies Gravitational lensing Large scale structure
Image credit: Hubble Space Telescope
Image credit: S. Gottlöber, G. Yepes, A. Klypin, A. Khalatyan
Image credit: http://www.nasa.gov/mission_pages/planck/
Total amount of DM
Planck Collaboration et al. 2013
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Image credit: http://cdms.berkeley.edu/Education/DMpages/science/directDetection.shtml
Image credit: Sky & Telescope / Gregg Dinderman
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Figures from Cirelli 2012
Indirect detection experiments in the solar neighborhood show
Anti-proton flux Positron fraction e+/(e+ + e-) e+ + e- flux
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Figures from Cirelli 2012
Positron fraction e+/(e+ + e-) Anti-proton flux e+ + e- flux
DM annihilation.
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annihilation, then e- and e+ should be created everywhere in the Galactic DM halo.
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Positron
H
Dark Matter
+ H H H H
ISM and magnetic fields
+ + + + +
Dark Matter Halo
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e Spectrum Diffusion Energy Loss Source
is Lorentz factor
2
( )
e
E m c
is the space coordinate
is number density of e- and e+
d d d ( , ) ( , ) ( , ) ( , ) ( , ) ( , ) d d d n n n x K x x b x x Q x t
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We use a constant diffusion coefficient from Donato et al. 2004 & Delahaye et al. 2008
( ) K K
25 2 1
1.67 10 cm s , 0.7 K
d d d ( , ) ( , ) ( , ) ( , ) ( , ) ( , ) d d d n n n x K x x b x x Q x t
d d d ( , ) ( , ) ( , ) ( , ) ( , ) ( , ) d d d n n n x K x x b x x Q x t
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e - photon
e - thermal electron
e - hydrogen atom
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The electrons and positrons are produced from DM annihilation
DM Density Profile d d d ( , ) ( , ) ( , ) ( , ) ( , ) ( , ) d d d n n n x K x x b x x Q x t
2 0( )
( )
dm e dm
r m Q v r
DM Annihilation Cross-Section
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Navarro, Frenk &White 1997
s dm 3 s s
( ) 1 r r r r r
Characteristic Density
Characteristic Radius
Inner Logarithmic Slope
NFW Profile: =1
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The solution of e spectrum, depends on
d ( , ) d n r
d d (r, ) (r, ) (r, ) (r, ) (r, ) d d n n K b Q
Assuming steady-state + spherical symmetry
Tell us about the distribution of electrons and positrons from DM annihilation in a DM halo
Galactic properties (energy losses)
g
DM properties (Source term)
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Canonical Model
(ref 1.)
(ref 2.)
(ref 3.)
Fermi and HESS
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+ +
e-, e+ gas pressure
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2 2 e dm 1
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as a function of
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as a function of
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as a function of
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as a function of
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Image credit: NOAO, AURA, NSF, T.A.Rector
Circular velocity + DM pressure gradient
g
( ) ( ) ( ) ) d ( ) ( ) ( d
rot gas d dm m
P r r r r v r rg r rg r rg r
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without DM pressure with DM pressure Wechakama & Ascasibar MNRAS 2011
without DM pressure with DM pressure
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14 Low Surface Brightness Galaxies (de Blok & Bosma 2002)
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Observed Rotation Curve from de Blok&Bosma 2002
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star gas
Star & Gas Data from de Blok&Bosma 2002
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Rotation Curve Without DM pressure from de Blok&Bosma 2002
star gas
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1 GeV 100 MeV
Rotation Curve with DM Pressure HI g = 1 cm-3 Xion = 0
star gas
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Rotation Curve with DM Pressure HII g = 0.01 cm-3 Xion = 1
1 GeV 100 MeV
star gas
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Oh et al. (2011)
DM pressure might help to solve the cusp-core problem !!!!
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– up to kpc scales
– might help to solve the cusp-core problem
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Positron Dark Matter
+
e propagate and lose energy by ISRF, ISM and magnetic fields
H H H H H
+ + + +
Multi-wavelength photons are produced by synchrotron radiation and ICS Photons are produced by final state radiation (FSR)
Source Term Diffusion & Energy Losses Emission
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For synchrotron and ICS
Specific luminosity emitted by Syn.
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d ( , ) ( , ) ( , )d d n r r j
Depends on the properties of DM, diffusion and energy losses
For FSR
2 2 dm FSR dm
d ( ) 1 ( , ) 2 d( ) v r r h m h
Depends only on the properties of DM Depends on <σv>e
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( , ) ( , )d I r s
Figure from Springel et al. 2008
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Galactic properties (diffusion & energy losses)
g
K() DM properties (Source term)
Canonical Model
(ref 1.)
(ref 2.)
(ref 5.)
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Haslam 408 MHz (1 band) WMAP 23 – 94 GHz (5 bands) Fermi 0.3 – 300 GeV (12 bands)
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Intensity
Raw data After subtraction
All Sky Map
Masked Residual Map
b b
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by comparison of model and observed intensity
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Thermal Cross- section
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Navarro, Frenk &White 1997
s dm 3 s s
( ) 1 r r r r r
Characteristic Density
Characteristic Radius
Inner Logarithmic Slope
NFW Profile: =1
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NFW profile <σv>e = 3 x 10-26 cm3 s-1
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and synchrotron emission provide the tightest constraints at lower energies mdm < 20 GeV.
mdm > 20 - 30 GeV.
for mdm < 5 GeV.
α = 1.5 for mdm < 2 TeV.
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Image credit: Scientific American