Analysis of Spatial Structure of the Spica H II Region

Far ultraviolet (FUV) spectral images of the Spica H II region are first presented here for the Si II* {lambda}1533.4 and Al II {lambda}1670.8 lines and then compared with the optical H{alpha} image. The H{alpha} and Si II* images show enhanced emissions in the southern part of the H II region where H I density increases outward. This high density region, which we identify as part of the 'interaction ring' of the Loop I superbubble and the Local Bubble, seems to bound the southern H II region. On the other hand, the observed profile of Al II shows a broad central peak, without much difference between the northern and southern parts, which we suspect results from multiple resonant scattering. The extended tails seen in the radial profiles of the FUV intensities suggest that the nebula may be embedded in a warm ionized gas. Simulation with a spectral synthesis code yields values of the Lyman continuum luminosity and the effective temperature of the central star similar to previous estimates with 10{sup 46.2} photons s{sup -1} and 26,000 K, respectively, but the density of the northern H II region, 0.22 cm{sup -3}, is much smaller than previous estimates for the H{alpha} brightest region.