Antimatter in our Galaxy unveiled by INTEGRAL Jürgen Knödlseder Centre d’Etude Spatiale des Rayonnements, Toulouse, France

Antimatter annihilation E = m c 2

Galactic positron annihilation Morphology & Flux 3 components : - bulge - disk - PLE Bulge morphology highly uncertain Total flux : (1-3) x ph cm -2 s -1 Bulge / Disk flux ratio : Purcell et al OSSE, TGRS, SMM, … Kinzer et al Spectroscopy centroid ~ 511 keV Gaussian FWHM ~ keV positronium fraction 0.93 ± 0.04 The pre-INTEGRAL epoch

INTEGRAL ESA’s INTErnational Gamma-Ray Astrophysics Laboratory Launch : 17 october 2002 Mission duration : 2008 Orbit : 72 h, excentric Guest observer time : % IBIS : Imager on Board the Integral Satellite keV, 12’, R ≈ 12 SPI : SPectrometer onboard Integral keV, 2.5°, R ≈ 500 JEM-X : Joint European Monitor for X-rays keV, 3’, R ≈ 10 OMC : Optical Monitoring Camera550 nm (V band), 6"

SPI SPectrometer onboard INTEGRAL

SPI all-sky exposure after ~ first year Jürgen Knödlseder, Pierre Jean, Vincent Lonjou, Georg Weidenspointner, Nidhal Guessoum, William Gillard, Gerry Skinner, Peter von Ballmoos, Gilbert Vedrenne, Jean-Pierre Roques, Stéphane Schanne, Bonnard Teegarden, Volker Schönfelder, C. Winkler, submitted to A&A 10 7 cm 2 s 1 x 10 7 cm 2 s = 133 ks

maximum : 5 x ph cm -2 s -1 at GC large parts of galactic plane better than 2 x ph cm -2 s -1 several high latitude regions better than 2 x ph cm -2 s -1 SPI 511 keV point-source sensitivity ph cm -2 s -1

Background modelling Step 1

511 keV background ~ 5 % variations

511 keV background model r(t) = r cont (t) +  1 +  2 x g(t) +  3 x ∫ g(t’) x exp((t’-t)/  ) dt’ r cont (t) : continuum background (from adjacent energies) r(t) : predicted 511 keV line background rate g(t) : GEDSAT rate  = 352 days  1,  2,  3 : fitted coefficients (detector / orbit & detector) r cont (t) g(t) ∫ g(t’) x exp((t’-t)/  ) dt’ constant

Residuals 1 %

Model fitting Step 2

511 keV bulge emission morphology Modelling with a 2d Gaussian l ° ± 0.3° b ° ± 0.3°  l (FWHM)8.1° ± 0.9°  b (FWHM)7.2° ± 0.9°  b /  l0.89 ± keV flux 1.09 ± 0.04 (10 -3 ph cm -2 s -1 )

Bulge/Halo models SPI 511 keV bulge flux : ( ) x ph cm -2 s x ph cm -2 s x ph cm -2 s x ph cm -2 s x ph cm -2 s -1

Bulge/Halo + Disk models SPI flux (imaging) ( ) x ph cm -2 s -1 SMM flux (wide FOV)( ) x ph cm -2 s x ph cm -2 s x ph cm -2 s x ph cm -2 s x ph cm -2 s -1

Comparison with tracer maps FIRRadioNIRµ-wavesVX-ray  Old stellar population K+M giants XRBs Young stellar population (free-free, CO, cold dust)

Step 2 : Conclusions BulgeHaloDisk Flux (10 -3 ph cm -2 s -1 )1.05 ± ± ± 0.5 L 511 (10 43 ph s -1 )0.90 ± ± ± 0.1 L p (10 43 s -1 )*1.50 ± ± ± 0.2 * assuming f p = 0.93 The 511 keV line emission is bulge dominated : B/D flux ratio: B/D luminosity ratio: 3 - 9

Imaging Step 3

An all-sky image of 511 keV emission Iteration 17 of accelerated Richardson-Lucy algorithm 5° x 5° boxcar smoothing Integrated 511 keV flux : 1.4 x ph cm -2 s -1

Choice of iteration Iteration 1 Exposure Log likelihoodFlux

Choice of iteration Iteration 5 Exposure Log likelihoodFlux

Choice of iteration Iteration 10 Exposure Log likelihoodFlux

Choice of iteration Iteration 17 Exposure Log likelihoodFlux

Choice of iteration Iteration 25 Exposure Log likelihoodFlux

Choice of iteration Iteration 40 Exposure Log likelihoodFlux

Choice of iteration Iteration 70 Exposure Log likelihoodFlux

Choice of iteration Iteration 100 Exposure Log likelihoodFlux

511 keV line and Ps continuum emission Galactic Centre emission Weidenspointner et al. (2005) Positronium continuum same morphology Ps fraction ~98 %

Spectroscopy Step 4

Galactic bulge spectrum Model : Gauss + positronium + continuum Energy ± 0.03 keV FWHM 2.07 ± 0.10 keV Flux10.0 x ph cm -2 s -1

Galactic bulge spectrum Model : 2 Gauss + positronium + cont. Energy ± 0.03 keV FWHM ± 0.40 keV FWHM ± 1.11 keV Flux x ph cm -2 s -1 Flux x ph cm -2 s -1 Narrow Gauss (FWHM = 1.1 keV) : ~65 % Thermalised positrons Broad Gauss (FWHM = 5.1 keV) : ~35 % Inflight positronium formation (quenched if fully ionised) Consistent with 8000 K ISM with ionisation fraction of ~ Churazov et al. 2005

Comparison with OSSE Results basically consistent with OSSE - emission centred on GC - bulge dominates emission - flux consistent Results basically consistent with OSSE - emission centred on GC - bulge dominates emission - flux consistent SPI bulge slightly larger than OSSE bulge SPI bulge slightly larger than OSSE bulge No PLE (flux 3  < 1.5 x ph cm -2 s -1 ) No PLE (flux 3  < 1.5 x ph cm -2 s -1 ) QuantitySPI (1 yr)OSSE (9 yr) l ° ± 0.3° -0.25° ± 0.25° b ° ± 0.3°-0.3° ± 0.2°  l (FWHM)8.1° ± 0.9° 6.3° ± 1.5°  b (FWHM)7.2° ± 0.9°4.9° ± 0.7° 511 keV flux (10 -3 ph cm -2 s -1 ) B/D flux ratio

Constraints on the disk source 511 keV1809 keV ( 26 Al) 26 Al decays via  + decay (85%) F 511 = 0.5 x F 1809 (f p = 0.93) Expected : 5 x ph cm -2 s Sc decays via  + decay (99%) M 44 ~ 4 x M  yr -1 (chem. evol.) Morphology and escape fraction unknown Expected : 8 x ph cm -2 s -1 Observed disk flux ~ (4-8) x ph cm -2 s -1 Observed disk flux ~ (4-8) x ph cm -2 s -1 60% - 100% of the disk flux can be explained by 26 Al 60% - 100% of the disk flux can be explained by 26 Al Rest (if any) is comfortably explained by 44 Ti Rest (if any) is comfortably explained by 44 Ti There seems to exist a pure bulge positron source ! There seems to exist a pure bulge positron source !

Constraints on the bulge source Wolf-Rayet stars Hypernovae / GRB Core-collapse SNe Pulsars CR interactions with ISM Dark matter SN Ia Novae HMXB LMXB Stellar flares

Constraints on the bulge source Wolf-Rayet stars Hypernovae / GRB Core-collapse SNe Pulsars CR interactions with ISM Dark matter SN Ia Novae HMXB LMXB Stellar flares Strong disk component expected

Constraints on the bulge source Wolf-Rayet stars Hypernovae / GRB Core-collapse SNe Pulsars CR interactions with ISM Dark matter SN Ia Novae HMXB LMXB Stellar flares

Constraints on the bulge source Dark matter SN Ia Novae LMXB

Low-mass X-ray binaries Positron production processes  +   e + + e - (pair jet) N + N’  N*  N + e +Uncertainties Yield Line shape (broad versus narrow) Grimm et al Observed LMXB B/D ~ 1 Liu et al. 2000,2001 B/D too small ? (completeness) B/D too small ? (completeness) Why only LMXB and not HMXB ? Why only LMXB and not HMXB ?

Novae Positron production processes 13 N  13 C (  = 14 min, 100%) 18 F  18 O (  = 2.6 hr, 97%) 22 Na  22 Ne (  = 3.8 yr, 90%) 26 Al  26 Mg (  = 10 6 yr, 85%) Uncertainties B/D ratio (values up to 4 proposed for M31) M31 : 2 types of novae (bulge & disk) bulge : slow-dim, associated with CO disk : fast-bright, associated with ONe Nova rate (20-40 per year) Escape fractions (important for 13 N and 18 F) B/D probably OK (in particular if only CO novae contribute) B/D probably OK (in particular if only CO novae contribute) 13 N : if 100% escape  bulge CO nova rate 25 century -1 required (but models predict that 13 N e + are absorbed in expanding shell) 13 N : if 100% escape  bulge CO nova rate 25 century -1 required (but models predict that 13 N e + are absorbed in expanding shell) Yields YieldsCO (0.8 M  ) ONe (1.25 M  ) 13 N2 x x F2 x x Na7 x x Al2 x x Hernanz et al. 2001

Type Ia supernovae Positron production processes 57 Ni  57 Co (  = 52 hr, 40%) 56 Co  56 Fe (  = 111 d, 19%) 44 Sc  44 Ca (  = 5.4 hr (87 yr), 99%) Uncertainties B/D ratio (poorly known) SN Ia explosion mechanism SN Ia rate ( per century) Escape fraction (important for 57 Ni and 56 Co) 57 Ni : no chance for positrons to escape 57 Ni : no chance for positrons to escape 56 Co : 3% escape would require bulge rate of 0.6 century Co : 3% escape would require bulge rate of 0.6 century Sc : always escape, Sub-Ch would require bulge rate of century -1 (but : overproduces galactic 44 Ca abundance & makes bright 44 Ti bulge) 44 Sc : always escape, Sub-Ch would require bulge rate of century -1 (but : overproduces galactic 44 Ca abundance & makes bright 44 Ti bulge) Different types of SN Ia in bulge (underluminous) and disk (overluminous) ? Different types of SN Ia in bulge (underluminous) and disk (overluminous) ? Yields Yields ChSub-Ch 57 Ni Co Sc(7-20) x (1-4) x Woosley 1997; Woosley & Weaver 1994

Dark matter Distribution not well known Distribution not well known No flux prediction No flux prediction Sgr dwarf not detected Sgr dwarf not detected

General conclusions The 511 keV sky is bulge / halo dominated (B/D > 3) The 511 keV sky is bulge / halo dominated (B/D > 3) Besides bulge / halo and disk, no further 511 keV emission is observed (no PLE) Besides bulge / halo and disk, no further 511 keV emission is observed (no PLE) The disk component can be entierly explained by  + decay of radioactive 26 Al and 44 Ti The disk component can be entierly explained by  + decay of radioactive 26 Al and 44 Ti The origin of the bulge component is still mysterious (LMXB, Novae, SN Ia, dark matter ?) The origin of the bulge component is still mysterious (LMXB, Novae, SN Ia, dark matter ?) What is the bulge / halo e + source ? What is the bulge / halo e + source ? Has the bulge / halo e + source a disk component ? Has the bulge / halo e + source a disk component ? Can we learn something about SN Ia / Novae distribution and types ? Can we learn something about SN Ia / Novae distribution and types ? Observe nearby candidate sources (SNR, LMXB) Observe nearby candidate sources (SNR, LMXB) Deep observations at high galactic latitudes & galactic plane Deep observations at high galactic latitudes & galactic plane