Spectral and intensity variations of Galactic 26^Al emission

TL;DR

This study uses INTEGRAL gamma-ray data to analyze the distribution, spectral characteristics, and dynamics of 26Al emission in the Galaxy, providing insights into nucleosynthesis and Galactic rotation effects.

Contribution

First detailed spectral and spatial analysis of 26Al emission across the Galaxy using INTEGRAL data, constraining line broadening, distribution, and Galactic rotation effects.

Findings

Detected 26Al line at 28σ significance in the inner Galaxy.

Constrained line broadening to <1.3 keV, indicating narrow emission.

Measured 26Al mass in the Galaxy as approximately 2.7 solar masses.

Abstract

Gamma-ray line emission from the radioactive decay of 26Al reflects nucleosynthesis in massive stars and supernovae. We use INTEGRAL 26Al measurements to characterize the distribution and characteristics of 26Al source regions throughout the Galaxy. We detect the 26Al line from the inner Galaxy at 28\sigma significance. The line appears narrow, and we constrain broadening in the source regions to <1.3 keV (2\sigma). Different sky distribution models do not significantly affect those large-scale results. The 26Al intensity for the inner Galaxy is derived as (2.9\pm 0.2)\times 10^{-4}ph\ cm^{-2} s^{-1} rad^{-1}, consistent with earlier results from COMPTEL and SPI data. This can be translated to an 26Al mass of 2.7\pm 0.7 solar mass in the Galaxy as a whole. The 26Al intensity is also confirmed to be somewhat brighter in the 4th than in the 1st quadrant (ratio 1.3\pm 0.2). 26Al spectra separately derived for regions along the Galactic plane show clear line centroid shifts, attributed largely to the Galaxy's large-scale rotation. The 26Al line toward the direction of the Aquila region (20deg < l < 40deg) appears somewhat broadened. Latitudinal variations of 26Al emission towards the inner Galaxy are studied, finding a latitudinal scale height of 130^{+120}_{-70} pc (1\sigma) for 26Al in the inner Galaxy and a hint of peculiar 26Al emission towards the region l<0deg, b>5deg.