## 4. The spatial distribution of O VIOur data allow to investigate the distribution of O VI in the galactic halo. The absorption equivalent widths have been calculated from the result of the fits. Assuming that absorption is optically thin, the column density can be calculated from The column densities for all targets are given in Table 1. If we assume a hydrostatic Galactic halo (corona) of the type postulated by Spitzer (1956), we have an exponential density distribution of O VI , described by the equation with the O VI midplane density and scale height . The projected column density is then given by Fig. 4 shows the result we found when fitting equation (3) to our column densities. Best values for the parameters and
resulting from our We should note here that relies almost exclusively on the LMC measurements. To set an approximate lower limit for the scaleheight we applied the fit procedure to a dataset where the extragalactic stars are excluded. The result is kpc, and points to a substantially larger scaleheight of O VI in the halo than previous measurements do. The upper limit is 20 kpc. © European Southern Observatory (ESO) 1998 Online publication: September 8, 1998 |