G326.3$-$1.8. In particular, we investigate its energy-dependent morphology and model the emission with different templates. We also report a spectral analysis of our best models using two spatial components for the $\gamma$-ray emission and derive physical properties using one-zone models for the SNR spectrum.

*Fermi*-LAT and Pass 8 description \[sec:Fermi\]
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The Large Area Telescope (LAT) on board the $\textit{Fermi}$ satellite is a pair-conversion instrument sensitive to $\gamma$ rays in the energy range from 30 MeV to more than 300 GeV.\
Since the launch in August 2008, the $\textit{Fermi}$-LAT event reconstruction algorithm has been progressively upgraded to make use of the increasing understanding of the instrument performance as well as the environment in which it operates. Following Pass 7, released in August 2011, Pass 8 is the latest version of the $\textit{Fermi}$-LAT data release [@Pass8:Atwood:2013]. The enhanced reconstruction and classification algorithms result in improvements of the effective area, the PSF and the energy resolution. One major advance with respect to previous releases is the classification of detected photon events according to their reconstruction quality. The data set is hence divided into types of events with different energy or angular reconstruction qualities. The PSF selection divides the data into four parts: 