many factors, such as object latitude, array configuration and data flagging. The typical major and minor axes are 18.3 and 9.0 arcsec, respectively.

We estimate the noise level of the continuum image ($\sigma_\mathrm{bkg}$) by computing the standard deviation of 3-$\sigma$ clipped pixel values in a $10'\times10'$ region centred at the galaxy. Within this region, any 3-$\sigma$ detected source is masked out to avoid source contamination. We note that the detail of the mask is not important because the original pixel histogram in the region is noise dominated. The size of the region is selected to be sufficiently large to get meaningful background noise, but small enough to represent the local noise level at the position of our galaxy (the rms is usually worse at the edge of the image due to the primary beam correction). The typical rms of our continuum image is $\sim0.05$ mJy/beam. Our continuum images of NGC 253 and NGC 4945 are discarded due to strong cleaning residuals, which significantly degrade the image quality. We use literature values instead for these two galaxies and any other galaxy without LVHIS broad band continuum data. Polarization data are not used for this study.

1.4 GHz flux density measurement
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