Post on 25-Feb-2016
description
PRESENT AND FUTUREDARK MATTER SEARCHES WITH
IMAGING ATMOSPHERIC CHERENKOV TELESCOPES
J-F. GlicensteinIRFU, CEA-Saclay
Outline
− Imaging Atmospheric Cherenkov Telescopes− Indirect dark matter searches with IACT− Results on the Galactic Halo (H.E.S.S)− Dwarf Galaxies: Segue (MAGIC, VERITAS)− Galaxy clusters: Fornax (H.E.S.S)− Dark matter searches with CTA
3
Major Active IACTs
H.E.S.S.
MAGIC
VERITAS
High Energy Stereoscopic System
located in Namibia, latitude=-23o, altitude=1800 m4 telescopes, 107 m2 eachcameras 960 PMTFOV= 5o
trigger threshold=100GeVinstalled: january 2004
installation of 5th telescope in 2011, first light expected 2012mirror: 600m2, 2048 PMT, FOV=3.5o, trigger threshold=20 GeV
Major Atmospheric Gamma-ray Imaging Cherenkov
located in La Palma (Canaries Islands),latitude=+29o, altitude=2225 mmirror: 234 m2
camera 534 PMTFOV=3.5o
trigger threshold=60 GeVinstalled late 2004installation 2nd telescope in 2009mirror 234m2, 1099 PMT
Very Energetic Radiation Imaging Telescope Array System
origin: Whipple collaboration (10 m, late 80s)located in Arizona,latitude=+32o, altitude=1275 m
4 telescopes, 106 m2 eachcameras 499 PMTFOV=3.5o
trigger threshold=100 GeVinstalled in april 2007
Gamma- ray
~ 10 kmParticleshower
~ 1o
Cher
enko
v lig
ht
~ 120 m
1
2
3
4− brief flash ~3 ns− steroscopy: cosmic ray background rejection improved gamma ray reconstruction
Imaging atmospheric Cherenkov telescopes
Present and future DM searches with IACT 8
VHE gamma-ray astronomy: catalog of sources
Moriond Cosmology 2012
The VHE gamma-ray sky (November 2011)http://www.mppmu.mpg.de/~rwagner/sources/
~100 sources (60 galactic)
Present and future DM searches with IACT 9
Indirect DM searches with IACTs
Moriond Cosmology 2012
)(MTeV 1
/10 3
2
326-
Jscm
vdEdN
dEd
WIMP annihilation flux into rays observed by an IACT:
particle model fAP: dark halo model
− Most current particle models:− neutralinos (MSSM)− U Extra Dimensions (Servant, Tait 2003) boson B− leptophilic models (PAMELA excess) − decaying dark matter
− Astrophysical factor: dense targets
Galactic Center nearby dwarf galaxies, globular clusters galaxy clusters (Fornax)
dark matter clumps
dlJfsolDM
AP ..
2
Present and future DM searches with IACT 10
Signal boosts: particle physics
Moriond Cosmology 2012
FSR IB
relative velocity b
– Sommerfeld effect:• effective low velocity dispersions
• resonances at:
– Internal Brehmstrahlung• annihilation to W+W-,ff
( heavy higgsino-like)
03.02 bcv
TeV45.4 22
2
nnMM Z
Present and future DM searches with IACT 11
Signal boosts: astrophysics
Moriond Cosmology 2012
• Boost effect B from unresolved DM clumps• estimated with Aquarius simulation (Springel et al 2008)• B sensitive the assumed value of Mlim ( Mlim
-0.226)• B ~ (a few) for point-like searches towards dwarf galaxies• B up to 2 order of mag. for extended searches (galaxy clusters)
Mlim = 10-6 M ⊙
Mlim = 5 10-3 M ⊙
Fornax galaxy cluster
Present and future DM searches with IACT 12
HESS searches towards the Galactic halo
Moriond Cosmology 2012
− 112 hours collected (2004-2008)− 1 degree around GC− galactic plane (|b| < 0.3o) excluded− background estimated by reflected bakground technique
Present and future DM searches with IACT 13
H.E.S.S. limits on WIMP annihilation in the Galactic halo
Moriond Cosmology 2012
Excluded 95% C.L.
mSUGRA models
A.Abramovski et al. (HESS), Phys.Rev.Lett 106, 161301 (2011)
Present and future DM searches with IACT 14
Searches towards globular clusters: M15
Moriond Cosmology 2012
UMiDrac
oM15 (adiabatic compression)
MSSM + WMAP constraints
Same (Woods et al) DM halo modelling
Excluded (95% CL)
HESS limit
• very small 0.04 pc core• low metalicity(“primordial”)• not dominated by DM
WHIPPLE
• Woods et al (Whipple) 2008: constraints at the 10-23 level (1.2 hour!)• A.Abramovski et al (HESS) ApJ 735 11 (2011): also at 10-23 level (15.2 h)• takes into account heating of DM by stars in GC core
Present and future DM searches with IACT 15
Dwarf spheroidal galaxies
Moriond Cosmology 2012
• dark matter dominated• mass range: 107-109 M ⊙• observed by IACTs:
Sagittarius, Carina, Sculptor, Draco,Willman1, Segue1, Umin, Canis Major, Boötes 1
• data on surface brightness,velocity dispersion, globular clusters,colors galactic structure wellmodeled
Walker et al 2007
Belokurov et al 2006
Present and future DM searches with IACT 16
Segue 1 dwarf galaxy
Moriond Cosmology 2012
− discovered 2006 in the SEGUE (Sloan) catalog by Belokurov et al.− located 23±2 kpc from the Sun− located at the intersection of Saggitarius and Orphan stellar streams− unclear whether dwarf galaxy or globular cluster− only 71 stars resolved. − velocity dispersion =3.7±1.5 km/s M = 5.8 106 M⊙−seems dominated by DM, but error on mass ~ 100%
log (core radius)
MV
GC dwarfgalaxies
Present and future DM searches with IACT 17
MAGIC observations of Segue1 dwarf
Moriond Cosmology 2012
− single telescope observations (MAGIC1), taken in 2008-2009− ~ 29.5 h good data− no evidence for signal− Segue 1 dwarf model was modelled as an Einasto profile (Essig et al 2010)− analysis in a slightly extended region ||< 0.14o ( = 10-5 sr)− J() = 1.78 1019 GeV5/cm2 sr
Emin = 100 GeV
Present and future DM searches with IACT 18
MAGIC searches towards Segue1: MSUGRA exclusion
Moriond Cosmology 2012
Excluded 95% C.L.
2 errors on J()(uncertainty on M)
J.Aleksic et al. (MAGIC), JCAP 06 035(2011)
<v>min ~ 10-23 cm3s-1
( t+t-)
Present and future DM searches with IACT 19
VERITAS observations of Segue 1 dwarf
Moriond Cosmology 2012
− 48.7 hours obtained in 2010 and 2011− no evidence for signal− same Einasto profile than the MAGIC paper− analysis in region q < 0.12o
− J() = 7.7 1018 GeV5/cm2 sr
-Emin = 300 GeV-Significance of signal inside q<0.12o: 1.4
-”contamination” by bright star(h-Leonis) -removed from background evaluation
target
Present and future DM searches with IACT 20
VERITAS searches towards Segue 1: exclusion limits
Moriond Cosmology 2012
<v> min ~ 2 10-24 cm3 s-1
(t+t-)
<v> from thermal models
Excluded 95% C.L.
E.Aliu et al (VERITAS), PRD 85, 062001 (2012)
Present and future DM searches with IACT 21
VERITAS searches towards Segue 1: boosts
Moriond Cosmology 2012
Wino-like neutralino self-annihilation self-annihilation to a 250 GeV particle pair
E.Aliu et al (VERITAS), PRD 85, 062001 (2012)
Excluded 95% C.L.
<v> from thermal models
Present and future DM searches with IACT 22
Searches towards Segue 1: leptophilic models
Moriond Cosmology 2012
A fraction of parameter space excluded by MAGIC @ low energyand VERITAS @ high energy
MAGIC
VERITAS
Present and future DM searches with IACT 23
Sagittarius dwarf galaxy
Moriond Cosmology 2012
old limits
− recent observations of Sgr stream allows better modellingof Sgr Dwarf (closest dwarf)
−update on former HESS limitsby Viana et al (AstroparticlePhysics 2012)
− should be detectable with CTA (Mwimp a few TeV,200 h observation)−However, expected signal from msecond pulsars in M54 (background)also detectable at 4-60
HESS
CTA
Present and future DM searches with IACT 24
The Fornax galaxy cluster
Moriond Cosmology 2012
−distance d=19 Mpc−central galaxy NGC1399 with a passive SMBH (109 M ⊙) − total mass ~ 1014 M ⊙ , extends over 1 Mpc (6o)− dark matter distribution well studied with X-rays, globular clusters, stars etc− 2 approaches in modelling:
− assume NFW profile with concentration param. from virial mass (RB02)− use directly measured profiles
Schuberth et al (2009)
X rays
GC
Present and future DM searches with IACT 25
H.E.S.S. observations of the Fornax galaxy cluster
Moriond Cosmology 2012
− 14.5 hours of data obtained in 2005− “minimal energy” of observations: Emin = 260 GeV− boost effect expected from substructure signal in extended regions− signal region:
−q < 0.1o, significance S = 2.3 −q < 0.5o, significance S=1.2−q< 1o, significance S=0.6
Present and future DM searches with IACT 26
HESS limits on Fornax: effect of source extension
Moriond Cosmology 2012
Present and future DM searches with IACT 27
H.E.S.S. results on Fornax: WIMPs exclusion
Moriond Cosmology 2012
A. Abramovski et al., arXiv1202.5494 (2012), accepted in ApJ.
Present and future DM searches with IACT 28
H.E.S.S limits on Fornax: KK models
Moriond Cosmology 2012
Present and future DM searches with IACT 29
HESS results on Fornax: boost factors
Moriond Cosmology 2012
Excluded 95% CL
Present and future DM searches with IACT 30
The next generation of IACTs: CTA (2015)
Moriond Cosmology 2012
low energy sectionEthresh ~ 10 GeV
4 ø=23 m telescopes
core array100 GeV-10 TeV23 ø=12 m telescopes
high energy section32 ø=5-6 m tel.on 10 km2 area
2 arrays: north+south all-sky coverage
Present and future DM searches with IACT 31
Sensitivity of CTA
Moriond Cosmology 2012
x 10 flux sensitivity gain
energy range increase
Flux sensitivity for a 50 h observation
Present and future DM searches with IACT 32
Dwarf galaxy searches with CTA
Moriond Cosmology 2012
Low energy High energy
Several arrays layout studied
SculptorSegue 1
Courtesy A. VianaD.Nieto
Present and future DM searches with IACT 33
dwarf galaxies with CTA (2)
Moriond Cosmology 2012
Boos
t fa
ctor
A signal from Willman 1 or Segue 1 may be observable with CTAdepending on boost factor.
Present and future DM searches with IACT 34
Galactic plane flux sensitivity (CTA)
Moriond Cosmology 2012
― assume Emin = 50 GeV― 500 GeV WIMP annihilating to bb― x10 gain in effective area, x2 gain in hadron rejection― reaches 10-13 cm-2 s-1 sensitivity, except on new sources
~400 hours total
10 hours each bin
Present and future DM searches with IACT 35
Searches for clumps
Moriond Cosmology 2012
HESS sensitivity
― clumps from ViaLacteaII (Diemand, Kuhlen, Madau, 2008)―~104 resolved halos in MW (M>105Msol)― 103 random realizations (rotate the observer position @8.5 kpc)― 168±44 clumps inside HESS galactic survey
Present and future DM searches with IACT 36
Expected <v> limits with clumps (galactic plane)
Moriond Cosmology 2012
Missing one order of mag. to reach thermal <v>
P.Brun, E.Moulin,J.Diemand, J-F.G, PRD 83, 015003 (2011)
Present and future DM searches with IACT 37
Expected <v> limits with clumps (1/4 sky)
Moriond Cosmology 2012
P.Brun, E.Moulin,J.Diemand, J-F.G, PRD 83, 015003 (2011)
― 1/4 survey in ~6 years― assume 5 10-13 cm-2s-1 sensitivity (5 hour/bin)― number of subhalos: 3907±324― thermal WIMPs region reachable
Present and future DM searches with IACT
38
Conclusion
− Best constraints on <v> from observation by H.E.S.S of galactic halo
− Many observations of dwarf galaxies. Most stringent constraints from observation of Segue 1 (Magic & Veritas)
− The limits have important astrophysical systematics (GC vs dwarf galaxies, modelling)
− Constraints on DM annihilation in the Fornax cluster (H.E.S.S) competitive with those from dwarf.
− With planned array CTA, observations of Segue1, Willman1 reach the thermal annihilation region with proper boost− Searches for clump with CTA may give detections or
provide stringent constraints.
Moriond Cosmology 2012
Present and future DM searches with IACT
39
Back-up slides
Moriond Cosmology 2012
Present and future DM searches with IACT
40Moriond Cosmology 2012
Present and future DM searches with IACT
41Moriond Cosmology 2012
Present and future DM searches with IACT
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Present and future DM searches with IACT 43
HESS searches towards the Galactic halo
Moriond Cosmology 2012
Present and future DM searches with IACT
44
CTA: array design
target performances
Moriond Cosmology 2012
45Present and future DM searches with IACT
Moriond Cosmology 2012
Expectations for Galactic plane survey
― assumes ―x 2 improvement in hadron rejection―x 2 gain in angular resolution ―x 10 gain in effective area
overall increase in sensitivity of ~ 9― expect ~ 300 sources in -30 deg≤ l ≤ 30 deg.
Funk,Hinton,Hermann,Digel, arXiV0901.1885
HESS map of the Gal.plane, total exp ~500 hours
simulated CTA map, flat exposure ~ 5 hours/field