PRESENT AND FUTURE DARK MATTER SEARCHES WITH I MAGING A TMOSPHERIC C HERENKOV T ELESCOPES

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)


Indirect DM searches with IACTs


)(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


Signal boosts: particle physics


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


Signal boosts: astrophysics


• 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


HESS searches towards the Galactic halo


− 112 hours collected (2004-2008)− 1 degree around GC− galactic plane (|b| < 0.3o) excluded− background estimated by reflected bakground technique


H.E.S.S. limits on WIMP annihilation in the Galactic halo


Excluded 95% C.L.

mSUGRA models

A.Abramovski et al. (HESS), Phys.Rev.Lett 106, 161301 (2011)


Searches towards globular clusters: M15


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


Dwarf spheroidal galaxies


• 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


Segue 1 dwarf galaxy


− 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


MAGIC observations of Segue1 dwarf


− 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


MAGIC searches towards Segue1: MSUGRA exclusion


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-)


VERITAS observations of Segue 1 dwarf


− 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


VERITAS searches towards Segue 1: exclusion limits


<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)


VERITAS searches towards Segue 1: boosts


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


Searches towards Segue 1: leptophilic models


A fraction of parameter space excluded by MAGIC @ low energyand VERITAS @ high energy

MAGIC

VERITAS


Sagittarius dwarf galaxy


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


The Fornax galaxy cluster


−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


H.E.S.S. observations of the Fornax galaxy cluster


− 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


HESS limits on Fornax: effect of source extension



H.E.S.S. results on Fornax: WIMPs exclusion


A. Abramovski et al., arXiv1202.5494 (2012), accepted in ApJ.


H.E.S.S limits on Fornax: KK models



HESS results on Fornax: boost factors


Excluded 95% CL


The next generation of IACTs: CTA (2015)


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


Sensitivity of CTA


x 10 flux sensitivity gain

energy range increase

Flux sensitivity for a 50 h observation


Dwarf galaxy searches with CTA


Low energy High energy

Several arrays layout studied

SculptorSegue 1

Courtesy A. VianaD.Nieto


dwarf galaxies with CTA (2)


Boos

t fa

ctor

A signal from Willman 1 or Segue 1 may be observable with CTAdepending on boost factor.


Galactic plane flux sensitivity (CTA)


― 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


Searches for clumps


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


Expected <v> limits with clumps (galactic plane)


Missing one order of mag. to reach thermal <v>

P.Brun, E.Moulin,J.Diemand, J-F.G, PRD 83, 015003 (2011)


Expected <v> limits with clumps (1/4 sky)


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.



39

Back-up slides



40Moriond Cosmology 2012


HESS searches towards the Galactic halo



44

CTA: array design

target performances


45Present and future DM searches with IACT


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

PRESENT AND FUTURE DARK MATTER SEARCHES WITH I MAGING A TMOSPHERIC C HERENKOV T ELESCOPES

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