The Relationship Between Gas and Cirrus Dust Filaments at the Edge of the Expanding Shell in Eridanus

Abstract

At the boundary of a large expanding shell in Eridanus around l = 187°, b = −50° the morphology observed in the HI emission is well mimicked by the 100 μm surface brightness but with associated structures offset by as much as 0.°5. A point-to-point comparison between I100μm and NHI in filaments of neutral hydrogen and dust (IR cirrus) produces only a weak dependence. However, when I100μm at a cirrus dust peak is compared with NHI at the associated H i peak, a relationship closer to that reported by other workers is found. Preliminary CO observations have set low limits on the molecular gas in these filaments. Since the H i and dust in our region are associated with a large expanding shell (or superbubble), shocks may be responsible for separation of gas and dust. The existence of small-scale structure in both the HI and IR is noted. We conclude that attempts to correlate HI and IR must invoke high-resolution area surveys.