Astron. Astrophys. 336, L29-L32 (1998)

3. Conclusion

We have shown that the interpretation of the HST and IUE spectra obtained by Webb et al. is not unique. The data can as well be modeled with a low value of the D/H ratio if one accounts for spatial correlations in the large scale velocity field.

The RMC results may be tested, in principle, by additional observations of higher order Lyman lines with the same spectral resolution as Webb et al. used for Ly-. Indeed, if is asymmetric, this will show up in the profile shapes of the higher order Lyman lines. For the physical parameters listed in Table 1, the effect becomes visible starting from Ly-4 [the Ly-, -, - lines are insensitive to the asymmetry of due to their high optical depth]. Fig. 5 shows simulated spectra (convolved with a Gaussian instrumental profile of FWHM = 0.1 Å) for Ly-4 and Ly-12 using the same distributions depicted in Fig. 4 - dotted curves for model (e) and solid curves for model (c) of Table 1. The line shapes clearly depend on the velocity field structure and are asymmetric in general.

Fig. 5. The H I Ly-4 and Ly-12 mesoturbulent spectra for model (c) (solid curves) and (e) (dotted curves) in Table 1. Short dashed curves show microturbulent profiles calculated for the mean N(H I ) = cm-1 and the mean Doppler parameter b(H I ) = 25.5 km s-1 of the data by Webb et al. The spectra are convolved with a Gaussian instrumental profile of FWHM = 0.1 Å

© European Southern Observatory (ESO) 1998

Online publication: July 20, 1998
helpdesk.link@springer.de