Dark matter physics from

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Dark matter physics from gamma-ray all sky
surveys
Savvas M. Koushiappas T-6 ISR-1 Los Alamos
National Laboratory
EGRET
GLAST
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What can be learned from something like this?
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What can be learned from something like this?
A lot of high energy astrophysics
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What can be learned from something like this?
A lot of high energy astrophysics
Perhaps something about the Dark matter
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What can be learned from something like this?
A lot of high energy astrophysics
Look at resolved sources
Perhaps something about the Dark matter
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What can be learned from something like this?
A lot of high energy astrophysics
Look at resolved sources
Perhaps something about the Dark matter
Look at the diffuse background
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What can be learned from something like this?
A lot of high energy astrophysics
Look at resolved sources Structure and
substructure of dark matter halos
Perhaps something about the Dark matter
Look at the diffuse background The origin of the
background-gtAngular fluctuations
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What is the Universe made up of?
Inflation
Big Bang nucleosynthesis
Cosmic microwave background
Supernovae
Weak lensing
Rotation curves
Galaxy cluster abundance
Large scale structure
Gravitational lensing
Lyman-alpha forest
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Gamma-ray friendly dark matter candidate
Lightest neutralino
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(No Transcript)
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The dwarf satellite problem and its disputable
existance
Klypin et al. (1999), Moore et al. (1999)
Figure courtesy James Bullock
Constributing factors

• Changing the properties of dark matter
• Modifying the spectrum of density fluctuations
• Feedback mechanisms

More massive
From Kravtsov, Gnedin Klypin, ApJ, 609, 482
(2004), but see also Klypin et al. (1991),
Bullock, Kravtsov Weinberg (2000), Benson et
al.(2001), Somerville (2001)
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The Milky Way substructure

• Cosmology sets the formation time, and therefore
  the distribution and properties of dark halo
  substructure
• Uncertainties in cosmological parameters result
  in uncertainties in the modelling of dark
  substructure

From SMK, Zentner Walker (2004)
Spread in luminosity
More luminous in gamma rays
Spread in radius
R(t)/R0
M(t)/M0
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The Milky Way substructure

• Cosmology sets the formation time, and therefore
  the distribution and properties of dark halo
  substructure
• Uncertainties in cosmological parameters result
  in uncertainties in the modelling of dark
  substructure

From Calcaneo-Roldan Moore (1999)
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GLAST
If then
detectable subhalo per GLAST field of
view, need a 450 hour exposure with VERITAS to
detect the line emission.
GLAST
VERITAS
VERITAS
If a detection must
rely on serendipitous discovery
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If then there will be
detectable subhalo per GLAST field of
view-need a 450 hour exposure with VERITAS to
detect the line emission.
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If then there will be
detectable subhalo per GLAST field of
view-need a 450 hour exposure with VERITAS to
detect the line emission.
Q How can this be done better?
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If then there will be
detectable subhalo per GLAST field of
view-need a 450 hour exposure with VERITAS to
detect the line emission.
Q How can this be done better?
Design an instrument like VERITAS, but with an
effective area of 5(10) times larger. Then the
exposure needed to detect the line will be only
90(45) hours!!
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LMC
Disk
Wilkinson et al. (2006)
More dark matter dominated
Disk
Circular velocity
Fainter
Why not the LMC or the galactic center?

• There is a disc
• There is potentially a bar
• Baryons dominate, hence not clear as to what the
  dark matter distribution is

From Alves Nelson (2000)
Radius from the center
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Local group dwarf spheroidal systems
From Strigari et al., astro-ph/0603775
Line of sight velocity dispersion
L.O.S. velocity
Fornax
Line-of-sight projection
Increasing radius away from the center
Dwarf spheroidals are easier to study because
they are dark matter dominated
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Draco dSph
Strigari, SMK, Bullock Kaplinghat, in
preparation (2006)
Increasing luminosity
From Strigari et al., astro-ph/0603775
Core? But where?
Increasing mass
Large degeneracy between cusped and cored profiles
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Profumo Kamionkowski, astro-ph/0601249
Dark matter halos are predicted to be described
by Universal profiles.
CACTUS measurement 1 deg angular res.
Test this picture using a suite of local group
dwarf galaxies
If gamma-rays originate from WIMP annihilation,
profiles must be cusped!!!!!
Improved angular resolution can map the dark
matter profile
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Draco dSph
From Strigari, SMK, Bullock Kaplinghat, in
preparation (2006)
Increasing luminosity
From Strigari et al., astro-ph/0603775
Core? But where?
Increasing mass
Large degeneracy between cusped and cored profiles
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Current GLAST prospects call for a 0.1-0.5 sigma
detections from within the inner 0.3deg of Draco
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Current GLAST prospects call for a 0.1-0.5 sigma
detections from within the inner 0.3deg of Draco
Q How can this be done better?
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Current GLAST prospects call for a 0.1-0.5 sigma
detections from within the inner 0.3deg of Draco
Q How can this be done better?
Design an instrument like GLAST, with an
effective area of 103 times larger and an angular
resolution of 5. Then observe many local
dwarves to determine the universality of the
central dark matter distribution.
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Gamma-ray background fluctuations
Comoving emissivity
Scale-dependent bias
Z3
Z1
Correlation function
More strongly clustered
Z0.5
Z0
From Ciardi, Miniati Di Matteo (2004)
Larger scales
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Gamma-ray luminosity function-model dependent
Use correlations between X-ray (e.g. Hasinjer et
al. (2005)) and radio (e.g. Salamon Stecker
(1996)) properties of blazars, or fit the
redshift distribution (e.g. Chung Mukherjee
(1998))of EGRET blazars
GLAST few x 1000
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Gamma-ray background fluctuations
Comoving emissivity
Scale-dependent bias
Z3
Z1
Correlation function
More strongly clustered
Z0.5
Z0
From Ciardi, Miniati Di Matteo (2004)
Larger scales
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From Ando Komatsu, astro-ph/0512217
From Miniati, SMK Di Matteo, in preparation,
2006
Fluctuations 20
More power
Smaller scales
Fluctuations in the gamma-ray background provide
information about the source of the background
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It may be impossible to identify the source of
the gamma-ray background if the dark matter is
the neutralino
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It may be impossible to identify the source of
the gamma-ray background if the dark matter is
the neutralino
Q How can this be done better?
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It may be impossible to identify the source of
the gamma-ray background if the dark matter is
the neutralino
Q How can this be done better?
Design an instrument like GLAST, with a
reasonably high angular (5) and frequency
(lt10) resolution and with 106 times (Aefftexp)
in order to identify the background through the
line emission of SUSY dark matter background
angular fluctuations
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Summary

• Probing the Milky Way dark substructure
• Dark matter distribution in halos
• Source of the gamma-ray background

Based on current experiments
What is needed
Survey to identify the sources (GLAST) a
VERITAS class instrument with Aeff x 10
Not promising, but not impossible
A GLAST instrument with an Aeff x 103 and with an
angular resolution of 5 arcmin
Worst, but perhaps not impossible
Perhaps identified, difficult if it is the dark
matter distribution
A GLAST instrument with an Aeffx106!!