Interstellar Absorption Lines in the Spectrum of the Starburst Galaxy NGC 1705

I present a GHRS archival study of the interstellar absorption lines in theline-of-sight to the HI-rich starburst dwarf galaxy NGC 1705, in the 1170 to1740A range at ~ 120 km/s resolution. The absorption features arising due tophotospheric lines are distinctly different from the interstellar lines. Theinterstellar lines consist of three relatively narrow components at LSRvelocities of -20, 260 and 540 km/s and include absorption by neutral atoms,singly ionized atoms and atoms in higher ionization states. The analysispresented in this paper consists of (1) a list of all interstellar absorptionfeatures with > 3 sigma significance and their measured equivalent widths and(2) plots of the lines in the various atomic species together with the resultsof non-linear least square fit profiles to the observed data and (3)unpublished 21-cm maps from the Wakker & van Woerden survey showing thelarge-scale HI distribution in the region near the NGC 1705 sightline and highvelocity cloud HVC 487. Further, I report weak N I 1200A triplet absorption forthe supershell component, which in the absence of dust depletion and ionizationcorrections implies a low N abundance. A low N abundance for the supershell isconsistent with an interpretation of nucleosynthetic enrichment by time-delayed"primary" nitrogen production, the age estimate of 10 - 20 x 10^6 years for thecentral superstar cluster NGC 1705-1 (Heckman and Leitherer, 1997) and theunderabundance of Fe reported by Sahu and Blades (1997).Comment: 21 pages, AASTeX, 8 separate Postscript figure files, To appear in Astronomical Journal, September 1998 issu