Online material

Appendix A: Gamma-ray spectrum of M 31

Table A.1 provides the intensity values of the M 31 gamma-ray spectrum that is shown in Fig. 2. Statistical errors are at the 1σ confidence level, and the upper limit for the 16.6–50.0 GeV energy bin at the 2σ confidence level. Systematic errors include uncertainties in our knowledge of the effective area of the LAT and uncertainties in the modelling of diffuse Galactic gamma-ray emission. The former were determined using modifications of the instrument response functions that bracket the uncertainties in our knowledge of the LAT effective area. The latter were determined by deriving spectra for variations of the diffuse Galactic models that make use of either an E(B−V) template or for which the gas templates have been replaced by the IRIS 100 μm map, from which emission associated to M 31 has been removed. Both types of systematic uncertainties were added linearily.

The last column gives the number of counts attributed to M 31 in each of the energy bins from the fit of a spatial model to the present data.

© ESO, 2010