The isotopes ^ { 60 } Fe and ^ { 26 } Al originate from massive stars and their supernovae , reflecting ongoing nucleosynthesis in the Galaxy .
We studied the gamma-ray emission from these isotopes at characteristic energies 1173 , 1332 , and 1809 keV with over 15 years of SPI data , finding a line flux in ^ { 60 } Fe combined lines of ( 0.31 \pm 0.06 ) \times 10 ^ { -3 } \mathrm { ph cm ^ { -2 } s ^ { -1 } } and the ^ { 26 } Al line flux of ( 16.8 \pm 0.7 ) \times 10 ^ { -4 } \mathrm { ph cm ^ { -2 } s ^ { -1 } } above the background and continuum emission for the whole sky .
Based on the exponential-disk grid maps , we characterise the emission extent of ^ { 26 } Al to find scale parameters R _ { 0 } = 7.0 ^ { +1.5 } _ { -1.0 } kpc and z _ { 0 } = 0.8 ^ { +0.3 } _ { -0.2 } kpc , however the ^ { 60 } Fe lines are too weak to spatially constrain the emission .
Based on a point source model test across the Galactic plane , the ^ { 60 } Fe emission would not be consistent with a single strong point source in the Galactic center or somewhere else , providing a hint for a diffuse nature .
We carried out comparisons of emission morphology maps using different candidate-source tracers for both ^ { 26 } Al and ^ { 60 } Fe emissions , and suggests that the ^ { 60 } Fe emission is more likely to be concentrated towards the Galactic plane .
We determine the ^ { 60 } Fe / ^ { 26 } Al \gamma -ray flux ratio at ( 18.4 \pm 4.2 ) \% , when using a parameterized spatial morphology model .
Across the range of plausible morphologies , it appears possible that ^ { 26 } Al and ^ { 60 } Fe are distributed differently in the Galaxy .
Using the best fitting maps for each of the elements , we constrain flux ratios in the range 0.2–0.4 .
We discuss its implications for massive star models and their nucleosynthesis .