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Stefano ProfumoStefano ProfumoUC Santa CruzUC Santa Cruz
Santa Cruz Institute for Particle PhysicsSanta Cruz Institute for Particle Physics
T.A.S.C. [Theoretical Astrophysics in Santa Cruz]T.A.S.C. [Theoretical Astrophysics in Santa Cruz]
TeV Particle Astrophysics 2009
SLAC National Accelerator Laboratory, Menlo Park, CA,
July 13-17, 2009
New Physics with ACTsin the Fermi Era
Annihilation debris: an unavoidable
consequence of thermal WIMPs
Gamma Rays
1. “Primary”
• Hadronization, 0
• Final State Radition (e.g. L+L- )
(included in e.g. DMFIT)
• “Intermediate State” Radiation
(model-dependent, incl. in DSv5)
• Loop-suppressed radiative
annihilation modes (, Z, h, …)
Credit: Fermilab Website
1. Source TermdE
EdN
m
xxEQ e )(
v)(
),( rel2DM
2DM
2. Transport Equation ),(),(),( xEQdE
dnxEb
EdE
dnxED
dE
dn
teee
WIMP annihilation also produces stable Electrons and Positrons,which diffuse and loose energy
Inverse Compton off CMB and starlight photons, Bremsstrahlung and Synchrotron emission
produce radiation from radio to gamma-ray frequencies
3. Compute the Signals (IC off CMB/starlight, Synchrotron emission,…) ),(EQ xEne
Gamma Rays
1. “Primary”
2. “Secondary”
• Inverse Compton (e+e+)
(where from CMB, starlight, IRB…)
• Bremsstrahlung
• Synchrotron (for large enough B)
Credit: Fermilab Website
Annihilation debris: an unavoidable
consequence of thermal WIMPs
The multi-wavelength spectrum expected from a 41 GeV “bino” annihilating in the Coma cluster
Colafrancesco, Profumo and Ullio (2005)
“Environment”-dependent
(B, gas density, diffusion)
Set by the
DM particle
mass scale
What is “magic” about gamma-ray telescopes
for the search for dark matter?
~m
~ m-2
~ m2
~ m2/mZ4
~ 1/ ~ m-2
Baltz (2004)
They probe the energy range where
the thermal cold DM mass scale is
WIMP Mass
RangeSecondary & Low-E
Primary Radiation
Non-thermal
Production
Gamma-Ray
“Debris”
What is “magic” about gamma-ray telescopes
for the search for dark matter?
an “old”
Morselli plot
WIMP Mass
RangeSecondary & Low-E
Primary Radiation
Non-thermal
Production
What is “magic” about gamma-ray telescopes
for the search for dark matter?
Role of ACT’s in
the multi-frequency
siege to dark matter
in the Fermi Era
1. Dwarf Galaxies
2. GalaxyClusters
3. GalacticCenter
4. Cosmic RayElectrons/Positrons
1. Dwarfs: a lesson from CACTUS
Solar Array ACT located at Solar Two,
Daggett (CA), operated by UC Davis in ’04-’05
Observed PSR/SNR (Crab, Geminga),
AGN (Mk421, 501) and dSph Draco
Reported GR excess from Draco, later attributed to problems with noise assisted trigger threshold connected to starlight
dSph are DM dominated and GR-quiet objects: the usual suspect, DM interpretation of the excess
L.Bergstrom & D.Hooper, hep-ph/0512317 and S.Profumo & M.Kamionkowski, astro-ph/0601249
An important lesson: dSph are ideal targets for indirect DM searches
Moreover: ACTs are complementary to satellite-based GR telescopes[EGRET didn’t detect Draco]
1. Dwarfs: a lesson from CACTUS
S.Profumo & M.Kamionkowski, astro-ph/0601249
Exc
ess
Cou
nts
!!!
1. Dwarfs: general features of Fermi vs ACTdark matter search sensitivity
CACTUS signal huge cross section
ACT Limitation: low-energy threshold
ACT Asset: Great sensitivity to final states producing hard GR spectrum!
1. Dwarfs: Fermi results (T. Jeltema’s talk)
* Asset of Fermi: sensitivity to Inverse Compton Gamma Rays!
* Large Uncertainties on Diffusionin small extragalactic systems!
Preliminary
1. Dwarfs: Comparing MAGIC and Fermi
* Even without IC, the Fermi survey-modegives it an edge over ACTs
* Comparable sensitivities for m~1 TeV,~100h ACT obs. time
Preliminary
1. Dwarfs: prospects for ACTs in the Fermi era
Is it worth it forACTs to observe
local dSph to searchfor DM in the
Fermi era?
YES: one example:DM model that fitspositron excess
TeV particle
Large Diffusion in dSph
makes ACT much
better than Fermi!
Another example:Standard Neutralino-
type DM particle,negligible IC
m~1 TeV, comparablesensitivities for Fermi vs ACTs
m~5 TeV, ACTs canoutperform Fermi
1. Dwarfs: prospects for ACTs in the Fermi era
2. Clusters: a new gamma-ray source class?
* Largest bound dark matter structures
* Non-thermal activity detected as synchrotron radio emission
* Likely source of gamma rays from hadronic or leptonic primary cosmic rays
* Not conclusively detected so far in gamma rays
* Excess hard X radiation detected in a few cases
Galaxy Cluster Abell 1689 Warps Space Credit: N. Benitez (JHU)
2. Clusters: non-thermal activity from cosmic rays
Ophiuchus cluster (hard X-ray from Integral, new radio data)
Leptonic Scenarios alone fail to provide self-consistent explanation
Potential complementarity between Fermi and ACTs
Perez-Torres, Zandanel, Guerrero, Pal, Profumo, Prada and Panessa (2009)
2. Clusters: new physics versus cosmic rays
Signal from DM and from CR
in local clusters of galaxies
predicted to be comparable!
Jeltema, Kehaijas and Profumo (2009)
2. Clusters: new physics versus cosmic rays
Jeltema, Kehaijas and Profumo (2009)
Most promising targets for
New Physics: nearby
(gas-poor) galaxy groups!
2. Clusters: ACT and Fermi searches
H.E.S.S. Collaboration, A&A, astro-ph 0907.0727 (~8h observations)
2. Clusters: ACT and Fermi searches
See Tesla Jeltema’s talk; paper in preparation by Fermi Coll.
More targets, biased
towards those where
the DM/CR ratio is
larger, and brighter
Again, Fermi signal
dominated by IC,
HESS by FSR
Preliminary
3. The Milky Way Center and fundamental physics
Rich and complicated Region, with several sources,
large diffuse emission, non-thermal activity
3. The Milky Way Center and fundamental physics
ACT and Fermi observations of Sag A* of fundamental importance
to understand background to the (possibly) brightest DM source
3. The Milky Way Center and fundamental physics
Jeltema and Profumo (2008)
In the limit of perfect control over the diffuse and Sag A* “background”
Fermi can determine fundamental properties of DM from the GC
Regis and Ullio (2008)
Self-consistent treatment of both the Sag A* source and DM emission
must however include a multi-wavelength approach
3. The Milky Way Center and fundamental physics
Regis and Ullio (2008)
With certain assumptions on magnetic fields at the GC,
and on the DM annihilation final state
Radio and X-ray data put the gamma-ray emission beyond Fermi sensitivity,
marginally detectable by a CTA
3. The Milky Way Center and fundamental physics
4. Electrons and Positrons
Great data delivered by H.E.S.S.
on high-energy e+e- flux
Help understanding spectrum
and origin of HE e+e-
Relevance to New Physics:
1. Claim of anomalousfeatures related to e+ excess
2. Feeds back to diffusegalactic gamma ray emission
Bottom line of Fermi
e+e- analysis:
* Hard spectrum
* Compatible with
diffuse CR models
* Positron excess
requires extra
primary source
4. Electrons and Positrons
Is there an “anomalous feature” in the Fermi data alone?
Is there a residual “anomalous spectral feature”
in the Fermi data?
Most probably NO: in the ~ TeV range
• CR Source Spectrum Cutoff• Diffusion Radius comparable to mean SNR separation source stochasticity effects! [breakdown of spatial continuity and steady-state hypotheses]
1- band for largeset of random
SNR realizations
4. Electrons and Positrons: role of ACT’s
• Maximize overlap with Fermi data at >TeV
• Check for potential Anisotropy?
• Cross check HESS results with other ACT
• Re-calibrate ACT results after Fermi data with GR sources
• Follow-up on potential local sources of e+e-
ConclusionsNew Physics with ACTs in the Fermi Era
• Complementary Observations
(e.g. dwarfs, clusters, GC, e+e-)
• ACTs: Potential for Discovery
even in Fermi era
(e.g. clusters as new GR sources, dwarfs)
• Fundamental to understand
and control Background
(e.g. clusters, GC, e+e-)