2 The sample

Table 1 lists the barred galaxies that have been observed with the VLA (declinations north of $-39\hbox{$^\circ$ }$). These have an optical extent ${\ge} 4\hbox{$^\prime$ }$, to obtain reasonable spatial resolution, a mean total intensity in radio continuum of ${\ge} 3~{\rm mJy}/\mbox{arcmin}^2$, and were selected from Condon's (1987) survey. Our sample of galaxies observed with the ATCA (declinations south of $-39\hbox{$^\circ$ }$) is shown in Table 2. The criteria are the same, except for the size limit of 3$^\prime$. The isophotal major-axis diameter in arcmin is denoted by d₂₅, and q₂₅ is the ratio of the major-to-minor isophotal diameters; the subscript 25 refers to the isophotal level of 25 mag/ $\mbox{arcsec}^2$. The systemic velocity $v_{\rm GSR}$ has been transformed into distance D using H₀=75 km s^-1 Mpc^-1, except for NGC 1365 and NGC 4535, for which Cepheid distances are available (Madore et al. 1998; Macri et al. 1999). The inclination and position angle of each projected galaxy disc are denoted i and PA (Martin 1995; Martin & Friedli 1997; Ma et al. 1997, 1998; Wilke et al. 2000; Möllenhoff & Heidt 2001); i=0 means face-on and $\mbox{PA}=0$ is the north-south direction. For several southern galaxies, no values of i and PA are available, as indicated by "?''. The deprojected ratio of the bar's minor and major axes is denoted b/a, and 2a/d₂₅ is its relative length according to Elmegreen & Elmegreen (1985) or Martin (1995), derived from deprojected images according to the galaxy's inclination and position angle, assuming that the bars are flat. Values in brackets are our estimates from optical images.

The far-infrared flux densities at $\lambda60~ \mu$m, denoted $S_{60~\mu \rm m}$, are from Fullmer & Lonsdale (1989). Their values for NGC 2442 and NGC 3992 are obviously underestimated and were recalculated from the flux density at 100 $\mu$m using $S_{60~\mu \rm m} = fS_{100~\mu \rm m}$ with f=0.5 for the luminous galaxy NGC 2442 and f=0.3 for the faint galaxy NGC 3992 (see Fig. 5b in Young et al. 1989). The integrated radio continuum flux densities at $\lambda20~{\rm cm}$ and $\lambda6~{\rm cm}$, $S^{\rm tot}_{20~\rm cm}$ in Table 1 and $S^{\rm tot}_{6~\rm cm}$ in Table 2, were taken from Condon (1987) and Whiteoak (1970), respectively.