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

2. Galactic positron annihilation
The pre-INTEGRAL epoch
OSSE, TGRS, SMM, …
Purcell et al. 1997
Morphology & Flux
3 components : - bulge - disk - PLE
Bulge morphology highly uncertain
Total flux : (1-3) x 10-3 ph cm-2 s-1
Bulge / Disk flux ratio :
Spectroscopy
centroid ~ 511 keV
Gaussian FWHM ~ keV
positronium fraction 0.93 ± 0.04
Kinzer et al. 2001

3. SPI/INTEGRAL image of 511 keV emission
OSSE image (to scale)
Knödlseder et al astro-ph/
Iteration 17 of accelerated Richardson-Lucy algorithm
5° x 5° boxcar smoothing
Integrated 511 keV flux : 1.4 x 10-3 ph cm-2 s-1

4. 511 keV bulge emission morphology
Modelling with a 2d Gaussian
l ° ± 0.3°
b ° ± 0.3°
Dl (FWHM) 8.1° ± 0.9°
Db (FWHM) 7.2° ± 0.9°
Db / Dl ± 0.14
511 keV flux ± (10-3 ph cm-2 s-1)

5. Galaxy models compatible with SPI data
1.17 x 10-3 ph cm-2 s-1
2.15 x 10-3 ph cm-2 s-1
1.62 x 10-3 ph cm-2 s-1
2.04 x 10-3 ph cm-2 s-1
B/D ratio : 1-3 (flux) / 3-9 (luminosity)

6. Comparison with tracer maps
Old stellar population
K+M giants
XRBs
Young stellar population (free-free, CO, cold dust)
Radio
µ-waves
FIR
NIR V
X-ray g

7. Galactic bulge spectrum
Model : Gauss + positronium + continuum
Energy ± 0.03 keV
FWHM ± 0.10 keV
Flux 10.0 x 10-4 ph cm-2 s-1

8. Galactic bulge spectrum
Model : 2 Gauss + positronium + cont.
Energy ± 0.03 keV
FWHM ± 0.40 keV
FWHM ± 1.11 keV
Flux1 6.9 x 10-4 ph cm-2 s-1
Flux2 3.8 x 10-4 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

9. Constraints on the disk source
1809 keV (26Al)
511 keV
44Sc decays via b+ decay (99%)
M44 ~ 4 x 10-6 M yr-1 (chem. evol.)
Morphology and escape fraction unknown
Expected : 8 x 10-4 ph cm-2 s-1
26Al decays via b+ decay (85%)
F511 = 0.5 x F1809 (fp = 0.93)
Expected : 5 x 10-4 ph cm-2 s-1
Observed disk flux ~ (4-8) x 10-4 ph cm-2 s-1
60% - 100% of the disk flux can be explained by 26Al
Rest (if any) is comfortably explained by 44Ti
There seems to exist a pure bulge positron source !

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

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

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

13. Constraints on the bulge source
Dark matter
SN Ia
LMXB
Novae

14. Low-mass X-ray binaries
Positron production processes
g + g  e++ e- (pair jet)
N + N’  N*  N + e+
Uncertainties
Yield
Line shape (broad versus narrow)
Observed LMXB B/D ~ 1
Grimm et al. 2002
Liu et al. 2000,2001
B/D too small ? (completeness)
Why only LMXB and not HMXB ?

15. Novae B/D probably OK (in particular if only CO novae contribute)
Positron production processes
13N  13C (t = 14 min, 100%)
18F  18O (t = 2.6 hr, 97%)
22Na  22Ne (t = 3.8 yr, 90%)
26Al  26Mg (t = 106 yr, 85%)
Yields CO (0.8 M) ONe (1.25 M)
13N 2 x x 10-8
18F 2 x x 10-9
22Na 7 x x 10-9
26Al 2 x x 10-8
Hernanz et al. 2001
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 13N and 18F)
B/D probably OK (in particular if only CO novae contribute)
13N : if 100% escape  bulge CO nova rate 25 century-1 required (but models predict that 13N e+ are absorbed in expanding shell)

16. Type Ia supernovae 57Ni : no chance for positrons to escape
Positron production processes
57Ni  57Co (t = 52 hr, 40%)
56Co  56Fe (t = 111 d, 19%)
44Sc  44Ca (t = 5.4 hr (87 yr), 99%)
Yields Ch Sub-Ch
57Ni
56Co
44Sc (7-20) x 10-6 (1-4) x 10-3
Woosley 1997; Woosley & Weaver 1994
Uncertainties
B/D ratio (poorly known)
SN Ia explosion mechanism
SN Ia rate ( per century)
Escape fraction (important for 57Ni and 56Co)
57Ni : no chance for positrons to escape
56Co : 3% escape would require bulge rate of 0.6 century-1
44Sc : always escape, Sub-Ch would require bulge rate of century-1 (but : overproduces galactic 44Ca abundance & makes bright 44Ti bulge)
Different types of SN Ia in bulge (underluminous) and disk (overluminous) ?

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

18. General conclusions
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)
The disk component can be entierly explained by b+ decay of radioactive 26Al and 44Ti
The origin of the bulge component is still mysterious (LMXB, Novae, SN Ia, dark matter ?)
What is the bulge / halo e+ source ?
Has the bulge / halo e+ source a disk component ?
Can we learn something about SN Ia / Novae distribution and types ?
Observe nearby candidate sources (SNR, LMXB)
Deep observations at high galactic latitudes & galactic plane