Metallicity and physical conditions in the Magellanic Bridge

We present a new analysis of the diffuse gas in the Magellanic Bridge ( R. A. >= 3(h)) based on HST STIS E140M and FUSE spectra of two early- type stars lying within the Bridge and a QSO behind it. We derive the column densities of the HI ( from Ly alpha), Ni, OI, ArI, SiII, SII, and FeII of the gas in the Bridge. Using the atomic species, we determine the first gas- phase metallicity of the Magellanic Bridge, [Z/H] = - 1. 02 +/- 0: 07 toward one sight line and - 1: 7< [Z/ H] < - 0: 9 toward the other, a factor of 2 or more smaller than the present- day SMC metallicity. Using the metallicity and N( H I), we show that the Bridge gas along our three lines of sight is similar to 70% - 90% ionized, despite high H I columns, log N( HI) similar or equal to 19: 6 20: 1. Possible sources for the ongoing ionization are certainly the hot stars within the Bridge, hot gas ( revealed by O VI absorption), and leaking photons from the SMC and LMC. From the analysis of C II *, we deduce that the overall density of the Bridge must be low (< 0.03 - 0.1 cm(-3)). We argue that our findings combined with other recent observational results should motivate new models of the evolution of the SMC- LMC- Galaxy system.