6 HI-fluxes

HI-fluxes $F_{\rm HI}$ (Table 2, Col. 13) are expressed in Jy km s^-1 and corrected for beam-filling according to Bottinelli et al. (1990):

$$F_{\rm HI} = R\cdot F$$

where F is the observed raw HI-flux,

$$R = \left[ 1 + \frac{D_{25}^2\sin^2\beta + d_{25}^2\cos^2\beta} {22} \right]^{\frac{1}{2}}$$

and $\beta$ is the position angle of the galaxy defined north-eastwards, D₂₅ and d₂₅ are the photometric major and minor axis respectively.

  

Figure 4: Evolution of the HI-flux ($F_{\rm HI}/F_0$) of our 9 calibrating galaxies during the HI survey

  

Table 1: Calibrating galaxies

These fluxes have been first calibrated according to a set of close calibrating galaxies, whose HI-fluxes F₀ (see Table 1) were accurately measured by Fouqué (1982) and which have been regularly observed (once a month each on average) during all the period covered by our programme. The evolution of the ratio $F_{\rm HI}/F_0$with time allows us to supervise the Nançay system and to get for each observation the optimal flux measurement. We have exhibited four main periods of gain stability separated by ponctual steps which can be related to a change of either a diode or a cable along the acquisition chain (Fig. 4).