Context : The annihilation of positrons in the Galaxy ’ s interstellar medium produces characteristic gamma-rays with a line at 511 keV .
This gamma-ray emission has been observed with the spectrometer SPI on ESA ’ s INTEGRAL observatory , confirming a puzzling morphology with bright emission from an extended bulge-like region , while emission from the disk is faint .
Most known or plausible sources of positrons are , however , believed to be distributed throughout the disk of the Milky Way .

Aims : We aim to constrain characteristic spectral shapes for different spatial components in the disk and bulge using data with an exposure that has doubled since earlier reports .

Methods : We exploit high-resolution gamma-ray spectroscopy with SPI on INTEGRAL based on a new instrumental background method and detailed multi-component sky model fitting .

Results : We confirm the detection of the main extended components of characteristic annihilation gamma-ray signatures , altogether at 58 \sigma significance in the 511 keV line .
The total Galactic 511 keV line intensity amounts to ( 2.74 \pm 0.25 ) \times 10 ^ { -3 } ~ { } \mathrm { ph~ { } cm ^ { -2 } ~ { } s ^ { -1 } } for our assumed model of the spatial distribution .
We derive spectra for the bulge and disk , and a central source modelled as point-like and at the position of Sgr A* , and discuss spectral differences .
The bulge ( 56 \sigma ) shows a 511 keV line intensity of ( 0.96 \pm 0.07 ) \times 10 ^ { -3 } ~ { } \mathrm { ph~ { } cm ^ { -2 } ~ { } s ^ { -1 } } together with ortho-positronium continuum equivalent to a positronium fraction of ( 1.080 \pm 0.029 ) .
The two-dimensional Gaussian that represents the disk emission ( 12 \sigma ) has an extent of 60 ^ { +10 } _ { -5 } degrees in longitude and a rather large latitudinal extent of 10.5 ^ { +2.5 } _ { -1.5 } degrees ; the line intensity is ( 1.66 \pm 0.35 ) \times 10 ^ { -3 } ~ { } \mathrm { ph~ { } cm ^ { -2 } ~ { } s ^ { -1 } } with a marginal detection of the annihilation continuum and an overall diffuse Galactic continuum of ( 5.85 \pm 1.05 ) \times 10 ^ { -5 } ~ { } \mathrm { ph~ { } cm ^ { -2 } ~ { } s ^ { -1 } ~ { } keV ^ { -1 } } at 511 keV .
The disk shows no flux asymmetry between positive and negative longitudes , although spectral details differ .
The flux ratio between bulge and disk is ( 0.58 \pm 0.13 ) .
The central source ( 5 \sigma ) has an intensity of ( 0.80 \pm 0.19 ) \times 10 ^ { -4 } ~ { } \mathrm { ph~ { } cm ^ { -2 } ~ { } s ^ { -1 } } .

Conclusions :