Online Material

$\begin{figure} \par\includegraphics[width=18cm]{11870fg6.eps} \end{figure}$

Figure 6:

Galaxy NGC 0628 - Left panel: the color scale represents the image of the spectral index measured between 327 MHz and 1.4 GHz. Pixels with an intensity level above 3 $\sigma$ at both frequencies have been considered. Contours levels of the radio image at 1.4 GHz, starting from 3 $\sigma$ and scaling by a factor of $\sqrt {2}$ , are overlaid on the image. The FWHM of this image is $66\hbox {$^{\prime \prime }$ }\times 66\hbox {$^{\prime \prime }$ }$ . Right panel: the color scale represents the image of the spectral index uncertainty.

Open with DEXTER

$\begin{figure} \par\includegraphics[width=17.6cm]{11870fg7.eps} \end{figure}$	Figure 7: Galaxy NGC 0628: spectral index radial profile ( left panel) and spectral index variation with IR-70 $\mu$ m brightness ( right panel).
Open with DEXTER

$\begin{figure} \par\includegraphics[width=18cm]{11870fg8.eps} \end{figure}$

Figure 8:

Galaxy NGC 3627 - Left panel: the color scale represents the image of the spectral index measured between 327 MHz and 1.4 GHz. Pixels with an intensity level above 3 $\sigma$ at both frequencies have been considered. Contours levels of the radio image at 1.4 GHz, starting from 3 $\sigma$ and scaling by a factor of $\sqrt {2}$ , are overlaid on the image. The FWHM of this image is $20\hbox {$^{\prime \prime }$ }\times 20\hbox {$^{\prime \prime }$ }$ . Right panel: the color scale represents the image of the spectral index uncertainty.

Open with DEXTER

$\begin{figure} \par\includegraphics[width=17.65cm]{11870fg9.eps} \end{figure}$	Figure 9: Galaxy NGC 3627: Spectral index radial profile ( left panel) and spectral index variation with IR-70 $\mu$ m brightness ( right panel).
Open with DEXTER

$\begin{figure} \par\includegraphics[width=18cm]{11870fg10.eps} \end{figure}$

Figure 10:

Galaxy NGC 7331 - Left panel: the color scale represents the image of the spectral index measured between 327 MHz and 1.4 GHz. Pixels with an intensity level above 3 $\sigma$ at both frequencies have been considered. Contours levels of the radio image at 1.4 GHz, starting from 3 $\sigma$ and scaling by a factor of $\sqrt {2}$ , are overlaid on the image. The FWHM of this image is $20\hbox {$^{\prime \prime }$ }\times 20\hbox {$^{\prime \prime }$ }$ . Right panel: the color scale represents the image of the spectral index uncertainty.

Open with DEXTER

$\begin{figure} \par\includegraphics[width=18cm]{11870fg11.eps} \end{figure}$	Figure 11: Galaxy NGC 7331: spectral index radial profile ( left panel) and spectral index variation with IR-70 $\mu$ m brightness ( right panel).
Open with DEXTER