The whole procedure we have adopted to compute this is described in detail in Ramachandran et al. The results of the fit are given in Table 1 . A plot of vs. DM for 188 pulsars. The values have been scaled to 400 MHz. Stars in the plot represent our measurements given in Table 1 .
Open circles are from the decorrelation band width measurements, using the relation .
Filled circles are the directly measured values. The best fit models are plotted as lines. Figure 1 gives the spatial distribution of the pulsars across the Gum nebula as a function of the galactic coordinates. This must be primarily due to the fact that pulsars are mostly concentrated in the galactic disk and at such galactic longitudes toward the Galactic anti-center one does have significant contribution from the disk. Pulsars with high appear to lie behind the IRAS vela shell, as marked by the small circle in the figure.