Table 2:

Scale-lengths and relative contributions of the core component.

	M 81			M 100
Band	('')	Fit	fc	('')	Fit	fc
(1)	(2)	(3)	(4)	(5)	(6)	(7)
M 24 m	7.2	E+E	8.8	10.3	G+G	20.1
M 70 m	38.8	G+G	6.2	13.2	G+G	12.2
P 70 m	27.9	G+G	6.3	n.a.
M 160 m	28.5	G+G	0.3	5.14	G+G	3.5
P 160 m	26.4	G+G	1.2	n.a.
S 250 m	25.2	G+G	0.3	9.5	G+G	7.8
S 350 m	10.2	G+G	0.2	5.4	G+G	7.4
S 500 m	11.8	G+G	0.2	6.5	G+G	7.6

Notes. For M 99, the profile fit revealed no central component except at 24 m so we report this in the text. In column (1), M, P and S are MIPS, PACS and SPIRE, respectively, (2) and (5) the core component scale-length in arcseconds, (3) and (6) the best fit functions, E for exponential and G for Gaussian, and (4) and (7) the core component contribution to the total flux in %, respectively for M 81 and M 100. Relative uncertainties on the scale parameters are typically of , while on the core fractions these are typically