Transcript INDIRECT DARK MATTER SEARCHES WITH THE MAGIC TELESCOPE Michele Doro
INDIRECT DARK MATTER SEARCHES WITH THE MAGIC TELESCOPE Michele Doro
University of Padua (Italy)
SUMMARY
1. Indirect DM search 2. DM observation with IACTs 3. Past MAGIC observations 4. Present interests 5. Outlook and conclusions 28/04/2020 Michele Doro - IDM 2006 2
1a. General Scenario: neutralino
Standard Cosmological scenario considered: Cold Dark Matter (CDM)
Roszkowski hep-ex/0404052
CDM made out of WIMPs • Neutral • Weak interaction • Stable • Massive NON-BARYONIC origin!
Among other particle candidates, the SUSY-WIMPs candidate neutralino is considered 28/04/2020 Michele Doro - IDM 2006 3
1b. Annihilations into gammas
Choosen scenario: SUSY WIMP with Neutralino Products from self-annihilation , can be identified in the channels: • Antimatter (e+,antip) • neutrinos • gammas • broad • line (suppressed) Target of gamma-ray astronomy
Z
h
28/04/2020 Neutral particles can trace back emission source Michele Doro - IDM 2006 4
1b. Annihilations
Number of gammas above 100 GeV for different DM annihilation channels Haefliger and Stark 28/04/2020 Michele Doro - IDM 2006 Simulation withing mSUGRA after WMAP cuts A WIMP particle must have mass large enough to be detected above the energy threshold by MAGIC 5
1c. Spectrum and Flux
SPECTRUM: • After hadronization of quark-antiquark, the gamma-spectrum is a continuum up to the Neutralino mass • In addition there are very weak direct gamma emission lines Gamma Spectra Important for The annihilation rate proportional to the square of the density
v
of DM
m
2 2 DM-astronomy: is Bertone et al,2006 Look for accumulation region (“amplification sites”) Galactic center Other dense objects 28/04/2020 Michele Doro - IDM 2006 6
1c. Spectrum and Flux
The -ray flux [photons•cm -2 •s -1 thus calculated: •sr -1 ] above a threshold energy E 0 is ( ,
E
E
0 )
N
8
m
2
v
1
d
los
2 [
r
(
s
)]
ds
Pointing angle Telescope angular acceptance FLUX uncertainties: • Astrophysical : strong dependence on the amplification region spatial distribution Modelization of the radial profile necessary • Particle Physics : cross section and branching ratios of the Hinderance: uncertainties of several order of magnitude!
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1d. Targets
• 2 dependence • DM accumulation (“amplifiers”) Signal features: • Low or high flux • VHE domain • Small-extended active region • Possible high background by other astrophysical emitters The Imaging Atmospheric Cherenkov Technique is suitable for DM investigation 28/04/2020 Michele Doro - IDM 2006 Density Density squared Moore 8
2. The MAGIC telescope
•SITE: – Roque de Los Muchachos – Northern emisphere – Canary islands 2200m.asl •Collaboration: – 9 countries – 18 institutes – 150 physicists •Chronology – 2001 start construction – 2003/Oct Inauguration – 2004/Sept Start Cycle I – regular observation period – 2006/June Start Cycle II 2007 MAGIC II array 28/04/2020 Michele Doro - IDM 2006 9
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Gamma ray Particle shower ~ 1 o
Observation Technique
~ 10 km
PHYSICS OF SHOWERS 1. Cosmic rays and gammas cascades is impinge the atmosphere 2. Electromagnetic • e-e+ pairs • bremsstrahlung Cherenkov radiation and Hadronic cascades • pions and muons 3. Typical Cherenkov signal bluish light with few ns duration
~ 120 m
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Imaging technique
Proton shower
NSB event Hadronic shower Gamma shower Crab Nebula
ON (blue) Pointing direclt to the emitters OFF (red) Pointing somewhere in the dark sky close to the emitters 28/04/2020 Statistical interpretation: ON over OFF signal Michele Doro - IDM 2006 Gamma shower 11
2. The MAGIC telescope
Large collection area 236m 2 surface 10 5 m 2 eff. area Good 2.5% crab/50hour (10 flux -11 sensitivity ph/cm 2 /s) Low energy-threshold (at zenith)
50 GeV (trigger) 70-100 GeV (analysis)
Energy resolution
30% (100 GeV) 20% (1 TeV)
28/04/2020 Such a characteristics allow ground-based Cherenkov Telescopes as DM annihilation MAGIC to be candidated for observation of signals from Michele Doro - IDM 2006 12
3. Past observations The galactic Center
[ApJ Letters 638 L101 (2006)] • From distance and DM density criteria, the Galactic Center was a good candidate place for indirect searches for Dark Matter.
• Observed by CANGAROO, VERITAS, HESS (2004) and MAGIC (2005) – difference between observ.
– very good agreement between HESS and MAGIC spectrum and flux • Show clear VHE signal steady signal over 2 years UNCUT power law spectrum up to > 10 TeV 28/04/2020 Michele Doro - IDM 2006 13
3. Past observations The galactic Center
[ApJ Letters 638 L101 (2006)] • Signal from SUSY DM would not extend up to 10 TeV and spectral index should be different • Signal associated to astrophysical source: • Central Black Hole SgrA* • SNR SgrA East • SNR G0.9+0.1
• Emission mechanism still unknown CONCLUSION Even if DM signal exists is hidden by astrophysical objects or below the energy threshold Background is challenging to overcome!
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4. Candidates for observation
Proposals of candidates for observ.
(> June 2006) High M/L dwarf spheroid galaxies
Draco UMa
Mini-spike Model
Unidentified EGRET SOURCES High galactic latitude 28/04/2020
Some observations are ongoing
!
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4. Dwarf spheroid galaxies
Two possible candidates for the MAGIC telescope: • Draco • (Ursa Maior) Galaxies with • high mass, low luminosity (M/L) • low stellar gas, dust content • have large DM content good candidates for DM search • CLEAN from other astrophysical emitters reduced background 28/04/2020 Michele Doro - IDM 2006 16
4. Candidates for obs.
DRACO high M/L dwarf Draco – 75kpc distant – Up to 300M sun /L sun – The halo is the most constrained by observation: • Circular velocities • Age first stars even if still not definite flux unpredictable – Northern hemisphere,
culmination at 29 o
Ursa Mayor •recently discovered •100kpc distance •250pc large •500M sun /L sun (or more?) •unknown radial profile •can have very large flux 28/04/2020 Michele Doro - IDM 2006 17
4. Cycle II observations The mini-spikes model
Bertone, Zentner, Silk 2006 “ A New Signature of Dark Matter Annihilations: -Rays from Intermediate-Mass Black Holes ” and see presentation by G.Bertone at IDM2006 • • • • • • • The miny-spikes theory in short • Context: CDM IMBH (10 2 -10 6 M sun ) in the galactic halo during SMBH formation No merging, adiabatic growth Formation of associated “ mini-spike ” of DM (high density ) Annihilation rate 2 bright gamma-ray sources Spherically-symmetric about the Galactic Center (~100 1000) Identical cut-offs (DM mass) and similar spectra May provide “smoking-gun” evidence for DM 28/04/2020 Michele Doro - IDM 2006 18
4. The mini-spikes model
The DM from a clump scenario has typical spetrum: Cross-section and mass prefactor Radial profile Central core In most DM scenarios, there goes the problematic interplay between m and the spatial distribution which affects the flux estimation.
v, In the “spike” instead, the central plateau size r cut = r cut ( ,m ) in such a way it partially compensates for the pre-factor .
After calculation, FINAL FLUX DEPENDENCE section and mass is weaker : ( from cross
v
) 2 / 7
m
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4. Cycle II observations The mini-spikes model
Where and which are best candidates mini-spikes search?
• Galactic halo • Clean signal for • Should be many in number (100) First search among UNIDENTIFIED EGRET SOURCES Bertone, Zentner, Silk 2006 (scenario B) m m =100GeV =1 TeV Unidentified EGRET sources • More than 100… 28/04/2020 Michele Doro - IDM 2006 20
4. Cycle II observations The mini-spikes theory
• Unidentified EGRET sources Among the Un.EGRET.Src
• Search for high galactic latitude (signal is more clean) • Flux must be wavelengths GLAST!
stable • No counterpart at large • Problem in EGRET source position determination SMOKING GUN… Observe a set of unidentified EGRET sources with the same spectral index and cut-off at DM mass!
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4. Conclusions and…
CONCLUSIONS • The IACT technique is suitable to detect gammas final states of DM annihilations • • Problems in estimating the flux MAGIC has very threshold high sensitivity as , due to unknown radial profiles and cross-sections and mass and low energy • • Observations are ongoing with Dwarf galaxies large amount of DM are expected to be where The mini-spikes scenario could be a smoking gun as it gets rid of some strong parameter dependencies 28/04/2020 Michele Doro - IDM 2006 22
4. …Outlook
OUTLOOK 1. At the end of 2007 a MAGIC clone should be operating ( MAGIC I + MAGIC II ) • • • Enhanced sensitivity Lower energy threshold Better overall performances 2. Important collaboration with space-satellite telescope as GLAST MAGIC telescope I MAGIC telescope II 28/04/2020 Michele Doro - IDM 2006 23
Euaitw (Thank you)
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