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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 1
Black Holes as DM annihilation “boosters”
Gianfranco BERTONE
INFN, Padova
http://home.fnal.gov/~bertone
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 2
True surface density of DM, Moore et al. 2005
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 3
But annihilation fluxes depend on the density SQUARED
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 4
But annihilation fluxes depend on the density SQUARED
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 5
But this is a very naïve picture!•Potential wells near galactic centers are dominated by baryons•Black Holes are ubiquitous and dominate the innermost regions•Take advantage of new developments in Astrophysics andCosmology
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 6
Given all these uncertainties (plus the particle physicsuncertainties):
How can you convince particle physicists thatyou have actually discovered DM?
i.e. can Astrophysics provide a smoking-gun signature for DM?
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 7
(Somewhat arbitrary)
Black Holes: Definitions
Stellar Mass BHs
•Endpoint of stellar evolution•Indirectly observed•Robust evidence•Lower limits on mass from obs.
Intermediate Mass BHs
•Maybe form in Glob. clusters•Maybe observed as ULXs•Seed for SMBHs?•Speculative but probable!
Supermassive BHs
•Unknown origin•Ubiquitous!•Robust evidence•Mass correlated with host halo
M ≤ 102 M 102 M ≤ M ≤ 106 M 106 M ≤ M ≤ 109 M
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 8
Convincing evidence for BHs, right in our (cosmic) backyard
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 9
Where do the observed BHs come from?
CREDIT: Sloan Digital Sky Survey, Apache Point Observatory
•We don’t know! Butthey are ubiquitous
•High-redshift quasarssuggest that 109 MsunBHs were already inplace when the Universewas only 1Gyr old
•Circumstance that canbe understood in termsof rapid growth startingfrom massive seeds
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 10
Scenario I: Seeds of 102 Msun
•At z ≈18, first stars form (image:formation of a protostar, fromhttp://www.tomabel.com)
•Zero metallicity Pop III starswith masses in the range M ⋲ 60 -140 Msun and M > 260 Msuncollapse directly to black holes
•Stars with 140 < M/ Msun < 260disrupted by pulsation pairproduction instability, leavingbehind no remnant
Gebhardt, Rich, & Ho 2002, Heger,Fryer, Woosley, Langer and Hartmann2003; Madau & Rees 2001; Islam Taylor& Silk 2003
http://www.tomabel.com
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 11
Scenario II: Seeds of 105 Msun
•In halos with efficientmolecular hydrogen coolingand which do not experienceany major mergers, aprotogalactic disk forms andcan evolve uninterrupted.
•Effective viscosity transfersmass inward
•A baryonic mass of order 105
Msun loses its angularmomentum and is transferredto the center of the halo.
•Central object may be brieflypressure-supported, but iteventually collapses to form ablack hole
Koushiappas, Bullock & Dekel 2004
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 12
Conserve Mass & Angular Momentum:
γsp=!
Mf
iM
*Adiabatic* growth of a Black Hole:BHs as “Annihilation Boosters”!
9-2γ4-γ
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 13
Collisional growth of Spikes (in presence of Stellar Cusps)
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 14
An intuitive description of Dark Matter “Spikes”
GB & Merritt 2005
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 15
Populating the MW halo with mini-spikes
GB 2006
•Populate halos at high z with prescription from given IMBHs model
•Evolve mini-halos with semi-analytic codes (Zentner, Bullock 2003, Zentner et al. 2004)
•Obtain statistical realization of MW halo at z=0 (RED dots)
•Iterate (BLUE dots)
•Average results over realizations (GB, Zentner & Silk 2005)
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 16
Gamma-Rays from DM Mini-spikes around IMBHs
Inserting typical values for the DM candidate and the spike, we find inscenario II
•One would naïvely expect that the flux scales with σv/m2
•BUT The maximum density is higher for the pessimistic case, andrcut=rcut(m,\sigma v). This partially compensates for the decrease in fluxdue to the prefactor σv/m2
•The final luminosity of the objects is thus proportional to ~ (σv)2/7m−9/7
KEY POINT!
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 17
Gamma-Rays from DM Mini-spikes
Inserting typical values for the DM candidate and the spike, we find inscenario II
Note the normalization of the flux:
Each Black Hole would be as luminous
(in terms of annihilation radiation) as the whole Galaxy!!
KEY POINT!
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 18
IMBH Scenario 2 (105 Msun)
GB, Zentner & Silk 2005
Results:
•Very high fluxes!
•Sources off the disk(need large field ofview to search forthem)
•Tens of sources withIDENTICAL spectrum:smoking-gun for DM
•Scatter amongdifferent realizationsrelatively small
•Can use ACTs tostudy sources ≥ 300GeV
Smoking gun!
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 19
IMBH Scenario 2 (103 Msun)
GB, Zentner & Silk 2005
Alternative strategy:
Use MAGIC or otherACTs to re-observeselected unidentifiedEGRET (and GLAST…)sources.
Criteria for EGRET:
• Off the disk
• Appropriate spectrum
• Extrapolate spectra athigh energies for areasonable guess onthe detectability
Ongoing collaborationwith MAGIC group
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 20
Probe high mχ with ACTsFull-sky search with GLAST
Observational Strategies
HESS
MAGIC
VERITASFull-sky search, simulation
of sources and spectra
G. Busetto, R. Rando
Re-observation of EGRET
sources, selection of candidates
M. Doro, M. Gaug, M. Mariotti, V. Scalzotto
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 21
Antares IceCube
Interesting alternative: Neutrino Telescopes
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 22
Prospects for detection with Neutrino Telescopes
GB 2006
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 23
C O N C L U S I O N S
• BHs can effectively “boost” the DM annihilation signal
• Intermediate Mass Black Holes may represent a uniqueopportunity to discover Dark Matter particles
• GLAST can rule out this scenario or prove it right.Importance of ACTs (MAGIC, HESS, VERITAS,CANGAROO) in extending the search at higher energies
• Neutrino telescopes IceCube and ANTARES might be ableto detect neutrinos from mini-spikes
• Further applications: see talks of S. Ando (gamma-raybackground) and P. Brun (anti-matter) in the DM session!
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 24
Why “annihilations”?
Early Universe
X
Today
X
X
X
SM
SM
SM
SM
Rough estimate of the relic density:
Electroweak-scale cross sections can reproduce correct relicdensity. LSP in SUSY scenarios KK DM in UED scenarios are OK!!
X = DARK MATTER SM = STANDARD MODEL PARTICLE
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 25
Spectrum per annihilation
GB, Zentner & Silk 2005
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 26
Annihilation Radiation
Direct productionHadronization and
decay
Neutrinos•direct production
•decay of heavy quarks•hadronization followed by decay of charged pions,
PhotonsDirect production
Hadronization thenDecay of neutral pions
e+e- pairsDirect production
Hadronization thenDecay of charged pions
Initial State (X= χ or B(1))Relevant final states
X
X
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8/28/06 G. Bertone, BHs as DM annihilation “boosters”, TeVPA II Madison, WI 27
Interesting applications: Work in progress…
Ahn, Bertone, Merritt & Zhang 2006 Bertone, Brun & Salati 2006
Gamma-ray Background Anti-matter searches
PRELIMINARY
PRELIMINARY