Table 2: Exploring the parameter space for p and $\tau _0$ . The results of our adopted model are given in the first column. These results already take the opacity to photon escape into account.
F(E > E₀) p=2.3 p=2.3 p=2.3 p=2.2 p=2.2 p=2.2

$\tau_0=10$ Myr $\tau_0=5$ Myr $\tau_0=1$ Myr $\tau_0=10$ Myr $\tau_0=5$ Myr $\tau_0=1$ Myr

E₀=100 MeV
2.32E-8 2.36E-8 2.21E-8 2.95E-8 2.97E-8 2.75E-8

E₀=200 GeV 1.60E-12 1.23E-12 4.76E-13 4.04E-12 3.08E-12 1.15E-12

E₀=600 GeV 3.61E-13 2.67E-13 8.98E-14 1.00E-12 7.34E-13 2.40E-13

E₀=1 TeV 1.78E-13 1.29E-13 4.10E-14 5.16E-13 3.70E-13 1.14E-13

E₀=2 TeV 6.29E-14 4.46E-14 1.31E-14 1.92E-13 1.35E-13 3.87E-14

**Table 2:** Exploring the parameter space for p and $\tau _0$ . The results of our adopted model are given in the first column. These results already take the opacity to photon escape into account.
F(E > E₀)	p=2.3	p=2.3	p=2.3	p=2.2	p=2.2	p=2.2
	$\tau_0=10$ Myr	$\tau_0=5$ Myr	$\tau_0=1$ Myr	$\tau_0=10$ Myr	$\tau_0=5$ Myr	$\tau_0=1$ Myr
E₀=100 MeV	2.32E-8	2.36E-8	2.21E-8	2.95E-8	2.97E-8	2.75E-8
E₀=200 GeV	1.60E-12	1.23E-12	4.76E-13	4.04E-12	3.08E-12	1.15E-12
E₀=600 GeV	3.61E-13	2.67E-13	8.98E-14	1.00E-12	7.34E-13	2.40E-13
E₀=1 TeV	1.78E-13	1.29E-13	4.10E-14	5.16E-13	3.70E-13	1.14E-13
E₀=2 TeV	6.29E-14	4.46E-14	1.31E-14	1.92E-13	1.35E-13	3.87E-14

Source LaTeX | All tables | In the text

	1 Introduction
	2 CANGAROO observations of NGC 253
	3 Phenomenology of the central region of NGC 253
	4 Diffuse modelling
	5 Results
	6 HESS observations
	7 Concluding remarks
	References
	Online Material
	Appendix: Parameterizations of proton-proton cross sections for neutral pion decay