The Orion OB1 Association II. The Orion-Eridanus Bubble

Observations of the interstellar medium in the vicinity of the Orion OB1 association show a cavity filled with hot ionized gas, surrounded by an expanding shell of neutral hydrogen (the Orion-Eridanus Bubble). In this paper we examine this cavity and the surrounding bubble with the aid of data from the Leiden/Dwingeloo HI survey. We present neutral-hydrogen maps for the Orion-Eridanus region which allow identification of the HI filaments and arcs delineating the Bubble and derivation of its expansion velocity. The HI data are compared to X-ray, CO and IRAS 100 micron data. Using models of wind blown bubbles that take the density stratification of the Galactic HI layer into account we show that the stellar winds and supernovae from stars in Orion OB1 can account for the size as well as the expansion velocity of the HI shell. However, density inhomogeneities in the ambient interstellar medium cause significant discrepancies between our model and the observed shell.